Title of the invention: Carrier frequency setting method, motor drive system and carrier frequency setting device
Technical field
[0001]
　The present invention relates to a carrier frequency setting method, a motor drive system, and a carrier frequency setting device, and is particularly suitable for use in driving a motor using an inverter.
　The present application claims priority based on Japanese Patent Application No. 2018-126066 filed in Japan on July 2, 2018, the contents of which are incorporated herein by reference.
Background technology
[0002]
　A PWM (Pulse Width Modulation) control type inverter is used as a power supply device for driving a motor of a train, a hybrid vehicle, a home electric appliance, or the like. In such an inverter, the width of the pulse signal (time to turn on the pulse) is determined by comparing the carrier wave (for example, a triangular wave) with the voltage command signal, and the switching element (for example, IGBT (Insulated Gate Bipolar)) is determined according to the generated pulse signal. By turning on / off Transistor)), the input DC power is converted into AC power having the frequency required to drive the motor and supplied to the motor. When driving a motor, it is necessary to reduce the loss of the motor, reduce the loss in the inverter, and realize high efficiency of the motor drive system as a whole.
[0003]
　Patent Document 1 prepares table data that sets the relationship between the carrier frequency (carrier wave frequency) of PWM control that minimizes the total loss of the motor and the inverter and the electric angle frequency of the motor, and prepares the electric angle frequency of the motor. It is disclosed that the inverter is operated to drive the motor at the carrier frequency of PWM control corresponding to the detected value of.
[0004]
　Patent Documents 2 and 3 describe that the carrier frequency is set according to the rotation speed and torque of the motor.
　Specifically, in Patent Document 2, the carrier frequency is set to the lowest first frequency in the first region where the rotation speed of the motor is low and the torque of the motor is large. Further, in the second region where the rotation speed of the motor is higher than the rotation speed set in the first region and the torque of the motor is about the same as the torque set in the first region, the second region The carrier frequency is set to a second frequency higher than the frequency of 1. Further, the rotation speed of the motor is higher than the rotation speed set in the first region and the second region, and the torque of the motor is higher than the torque set in the first region and the second region. In the third region where the lower second torque is obtained, the carrier frequency is set to the highest third frequency.
[0005]
　Further, in Patent Document 3, a low carrier frequency is set in a region where the rotation speed of the motor is low and the torque of the motor is small, and the carrier frequency is set higher as the rotation speed of the motor increases. Patent Document 3 states that it is effective to lower the carrier frequency in the non-small torque region in the low rotation speed region.
Prior art literature
Patent documents
[0006]
Patent Document 1: Japanese Patent Application Laid-Open No. 2007-2822998
Patent Document 2: Japanese Patent Application Laid-Open No. 2008-22671
Patent Document 3: Japanese Patent Application Laid-Open No. 2009-171768
Outline of the invention
Problems to be solved by the invention
[0007]
　However, in the technique described in Patent Document 1, there is no reference to the carrier frequency when the torque of the motor fluctuates. Further, in the techniques described in Patent Documents 2 and 3, the carrier frequency is lowered when the torque of the motor is large. Patent Document 2 states that as the torque increases, the drive current of the motor increases and the current loss increases. Therefore, the current loss is reduced by lowering the carrier frequency. In Patent Document 3, the larger the torque, the larger the current, so the on-loss of the switching element increases, the loss of the inverter increases in the large torque region, and the lower the rotation speed of the motor, the more concentrated the flow is in each phase arm. Since the amount of current increases, the carrier frequency in the low rotation speed and non-small torque region is set low. Without being bound by such findings, the present inventor investigated the relationship between the torque of the motor and the total loss of the loss of the motor and the loss of the inverter for each rotation speed of the motor. It has been found that setting the carrier frequency by the method described may not be preferable from the viewpoint of the total efficiency calculated from the total loss of the motor loss and the inverter loss.
[0008]
　The present invention has been made in view of the above problems, and an object of the present invention is to enable the motor to be driven so that the total loss of the loss of the motor and the loss of the inverter is reduced.
Means to solve problems
[0009]
　The carrier frequency setting method of the present invention is a carrier frequency setting method for setting a carrier frequency in an inverter for driving a motor, and the loss of the inverter and the motor when the motor is driven by the inverter. The total loss, which is the sum of the losses, is derived by the loss derivation step and the loss derivation step, in which the torque generated in the motor, the rotation speed of the motor, and the carrier frequency in the inverter are made different from each other. Based on the derived total loss, the carrier frequency derivation step of deriving the carrier frequency at which the total loss is minimized as the optimum carrier frequency in each of the combination of the plurality of motors and the plurality of rotation speeds, and the carrier Based on the optimum carrier frequency derived by the frequency derivation step, the relationship derivation step of deriving the relationship between the torque of the motor and the optimum carrier frequency for each rotation speed of the motor and the relationship derivation step of the motor When the motor is driven after the relationship is memorized by the relationship storage step for storing the relationship derived for each rotation speed of the motor and the rotation of the motor and the command value of the torque of the motor. It is characterized by having a carrier frequency setting step of setting a carrier frequency according to a number of command values ​​based on the relationship.
[0010]
　A first example of the motor drive system of the present invention is a motor drive system including an inverter, a motor driven by receiving supply of AC power from the inverter, and a control device for controlling the operation of the inverter. The inverter has a switching element configured by using a wide band gap semiconductor, and the control device determines the relationship between the torque of the motor derived for each rotation speed of the motor and the carrier frequency in the inverter. Based on this, there is a carrier frequency setting means for setting the carrier frequency of the inverter, and the relationship between the torque of the motor and the carrier frequency derived for each rotation speed of the motor is such that when the torque of the motor increases, the carrier It is characterized by having a portion where the frequency becomes high.
　A second example of the motor drive system of the present invention is a motor drive system including an inverter, a motor driven by receiving supply of AC power from the inverter, and a control device for controlling the operation of the inverter. The inverter has a switching element configured by using a semiconductor other than the wideband gap semiconductor, and the control device has a torque of the motor derived for each rotation speed of the motor and a carrier frequency in the inverter. The carrier frequency setting means for setting the carrier frequency of the inverter is provided based on the above relationship, and the relationship between the torque of the motor and the carrier frequency derived for each rotation speed of the motor is related to the torque of the motor. However, the carrier frequency is characterized by having substantially the same value.
[0011]
　The carrier frequency setting device of the present invention is a carrier frequency setting device that sets a carrier frequency of an inverter for driving a motor, and the carrier frequency setting device is a torque of the motor, a loss of the inverter, and the motor. As a relationship with the optimum carrier frequency, which is the carrier frequency when the total loss, which is the sum of the losses, is minimized, when the inverter has a switching element configured by using a wide band gap semiconductor, the motor In the range where the torque of the motor is equal to or greater than the torque of the motor corresponding to the carrier frequency at which the optimum carrier frequency is the lowest value, when the torque of the motor increases, the optimum carrier frequency becomes higher. In the range where the torque of the motor is equal to or less than the torque of the motor corresponding to the carrier frequency at which the optimum carrier frequency becomes the minimum value, when the torque of the motor increases, the optimum carrier frequency further decreases. When the inverter has the switching element which is derived for each rotation speed of the motor and is configured by using a semiconductor other than the wide band gap semiconductor, the optimum carrier frequency is approximately the same regardless of the torque of the motor. A characteristic of a constant value is derived for each rotation speed of the motor, and the carrier frequency of the inverter is set based on the relationship between the torque of the motor and the optimum carrier frequency.
Effect of the invention
[0012]
　According to the present invention, the motor can be driven so that the total loss of the loss of the motor and the loss of the inverter becomes small.
A brief description of the drawing
[0013]
[Fig. 1] Fig. 1 is a diagram showing an example of a schematic configuration of a motor drive system.
FIG. 2-1 is a diagram showing a first embodiment, and is a diagram showing a measurement result of loss when the rotation speed ratio of the motor is 1.00 in a table format.
FIG. 2-2 is a diagram showing a first embodiment, and is a second diagram showing a measurement result of loss when the rotation speed ratio of the motor is 1.00 in a table format.
FIG. 3 is a diagram showing a first embodiment, and is a graph showing the relationship between the total efficiency ratio and the carrier frequency when the rotation speed ratio of the motor is 1.00.
FIG. 4-1 is a diagram showing a first embodiment, and is a graph showing the relationship between the total loss ratio and the carrier frequency when the rotation speed ratio of the motor is 1.00.
FIG. 4-2 is a diagram showing a first embodiment, and is a second diagram showing the relationship between the total loss ratio and the carrier frequency when the rotation speed ratio of the motor is 1.00 in a graph format.
FIG. 5-1 is a diagram showing a first embodiment, and is a diagram showing a measurement result of loss when the rotation speed ratio of the motor is 0.75 in a table format.
FIG. 5-2 is a diagram showing a first embodiment, and is a second diagram showing a measurement result of loss when the rotation speed ratio of the motor is 0.75 in a table format.
FIG. 5-3 is a diagram showing a first embodiment, and is a third diagram showing a measurement result of loss when the rotation speed ratio of the motor is 0.75 in a table format.
FIG. 6 is a diagram showing a first embodiment, and is a graph showing the relationship between the total efficiency ratio and the carrier frequency when the rotation speed ratio of the motor is 0.75.
FIG. 7-1 is a diagram showing a first embodiment, and is a graph showing the relationship between the total loss ratio and the carrier frequency when the rotation speed ratio of the motor is 0.75.
FIG. 7-2 is a diagram showing a first embodiment, and is a second diagram showing the relationship between the total loss ratio and the carrier frequency when the rotation speed ratio of the motor is 0.75 in a graph format.
FIG. 7-3 is a diagram showing a first embodiment, and is a third diagram showing the relationship between the total loss ratio and the carrier frequency when the rotation speed ratio of the motor is 0.75 in a graph format.
FIG. 8-1 is a diagram showing a first embodiment, and is a diagram showing a measurement result of loss when the rotation speed ratio of the motor is 0.50 in a table format.
FIG. 8-2 is a diagram showing a first embodiment, and is a second diagram showing a measurement result of loss when the rotation speed ratio of the motor is 0.50 in a table format.
FIG. 8-3 is a diagram showing a first embodiment, and is a third diagram showing a measurement result of loss when the rotation speed ratio of the motor is 0.50 in a table format.
FIG. 9 is a diagram showing a first embodiment, and is a graph showing the relationship between the total efficiency ratio and the carrier frequency when the rotation speed ratio of the motor is 0.50.
FIG. 10-1 is a diagram showing a first embodiment, and is a diagram showing the relationship between the total loss ratio and the carrier frequency when the rotation speed ratio of the motor is 0.50 in a graph format.
FIG. 10-2 is a diagram showing a first embodiment, and is a second diagram showing the relationship between the total loss ratio and the carrier frequency when the rotation speed ratio of the motor is 0.50 in a graph format.
FIG. 10-3 is a diagram showing a first embodiment, and is a third diagram showing the relationship between the total loss ratio and the carrier frequency when the rotation speed ratio of the motor is 0.50 in a graph format.
FIG. 11-1 is a diagram showing a first embodiment, and is a diagram showing a measurement result of loss when the rotation speed ratio of the motor is 0.25 in a table format.
FIG. 11-2 is a diagram showing a first embodiment, and is a second diagram showing a measurement result of loss when the rotation speed ratio of the motor is 0.25 in a table format.
FIG. 11-3 is a diagram showing a first embodiment, and is a third diagram showing a measurement result of loss when the rotation speed ratio of the motor is 0.25 in a table format.
FIG. 12 is a diagram showing a first embodiment, and is a graph showing the relationship between the total efficiency ratio and the carrier frequency when the rotation speed ratio of the motor is 0.25.
FIG. 13-1 is a diagram showing a first embodiment, and is a graph showing the relationship between the total loss ratio and the carrier frequency when the rotation speed ratio of the motor is 0.25.
FIG. 13-2 is a diagram showing a first embodiment, and is a second diagram showing the relationship between the total loss ratio and the carrier frequency when the rotation speed ratio of the motor is 0.25 in a graph format.
FIG. 13-3 is a diagram showing a first embodiment, and is a third diagram showing the relationship between the total loss ratio and the carrier frequency when the rotation speed ratio of the motor is 0.25 in a graph format.
FIG. 14 is a flowchart illustrating an example of a method of deriving the relationship between the torque of the motor M and the carrier frequency for each rotation speed of the motor M.
FIG. 15-1 is a diagram showing a second embodiment, and is a first diagram showing a measurement result of loss when the rotation speed ratio of the motor is 1.00 in a table format.
FIG. 15-2 is a diagram showing a second embodiment, and is a second diagram showing a measurement result of loss when the rotation speed ratio of the motor is 1.00 in a table format.
FIG. 16 is a diagram showing a second embodiment, and is a graph showing the relationship between the total efficiency ratio and the carrier frequency when the rotation speed ratio of the motor is 1.00.
FIG. 17-1 is a diagram showing a second embodiment, and is a first diagram showing the relationship between the total loss ratio and the carrier frequency when the rotation speed ratio of the motor is 1.00 in a graph format.
FIG. 17-2 is a diagram showing a second embodiment, and is a graph showing the relationship between the total loss ratio and the carrier frequency when the rotation speed ratio of the motor is 1.00.
FIG. 18-1 is a diagram showing a second embodiment, and is a first diagram showing a measurement result of loss when the rotation speed ratio of the motor is 0.75 in a table format.
FIG. 18-2 is a diagram showing a second embodiment, and is a second diagram showing a measurement result of loss when the rotation speed ratio of the motor is 0.75 in a table format.
FIG. 18-3 is a diagram showing a second embodiment, and is a third diagram showing a measurement result of loss when the rotation speed ratio of the motor is 0.75 in a table format.
FIG. 19 is a diagram showing a second embodiment, and is a graph showing the relationship between the total efficiency ratio and the carrier frequency when the rotation speed ratio of the motor is 0.75.
FIG. 20-1 is a diagram showing a second embodiment, and is a first diagram showing the relationship between the total loss ratio and the carrier frequency when the rotation speed ratio of the motor is 0.75 in a graph format.
FIG. 20-2 is a diagram showing a second embodiment, and is a graph showing the relationship between the total loss ratio and the carrier frequency when the rotation speed ratio of the motor is 0.75.
FIG. 20-3 is a diagram showing a second embodiment, and is a third diagram showing the relationship between the total loss ratio and the carrier frequency when the rotation speed ratio of the motor is 0.75 in a graph format.
FIG. 21-1 is a diagram showing a second embodiment, and is a first diagram showing a measurement result of loss when the rotation speed ratio of the motor is 0.50 in a tabular format.
FIG. 21-2 is a diagram showing a second embodiment, and is a second diagram showing a measurement result of loss when the rotation speed ratio of the motor is 0.50 in a table format.
FIG. 21-3 is a diagram showing a second embodiment, and is a third diagram showing a measurement result of loss when the rotation speed ratio of the motor is 0.50 in a table format.
FIG. 22 is a diagram showing a second embodiment, and is a graph showing the relationship between the total efficiency ratio and the carrier frequency when the rotation speed ratio of the motor is 0.50.
FIG. 23-1 is a diagram showing a second embodiment, and is a diagram showing the relationship between the total loss ratio and the carrier frequency when the rotation speed ratio of the motor is 0.50 in a graph format.
FIG. 23-2 is a diagram showing a second embodiment, and is a graph showing the relationship between the total loss ratio and the carrier frequency when the rotation speed ratio of the motor is 0.50.
FIG. 23-3 is a diagram showing a second embodiment, and is a third diagram showing the relationship between the total loss ratio and the carrier frequency when the rotation speed ratio of the motor is 0.50 in a graph format.
FIG. 24-1 is a diagram showing a second embodiment, and is a diagram showing a measurement result of loss when the rotation speed ratio of the motor is 0.25 in a table format.
FIG. 24-2 is a diagram showing a second embodiment, and is a second diagram showing a measurement result of loss when the rotation speed ratio of the motor is 0.25 in a table format.
FIG. 24-3 is a diagram showing a second embodiment, and is a third diagram showing a measurement result of loss when the rotation speed ratio of the motor is 0.25 in a table format.
FIG. 25 is a diagram showing a second embodiment, and is a graph showing the relationship between the total efficiency ratio and the carrier frequency when the rotation speed ratio of the motor is 0.25.
FIG. 26-1 is a diagram showing a second embodiment, and is a diagram showing the relationship between the total loss ratio and the carrier frequency when the rotation speed ratio of the motor is 0.25 in a graph format.
FIG. 26-2 is a diagram showing a second embodiment, and is a graph showing the relationship between the total loss ratio and the carrier frequency when the rotation speed ratio of the motor is 0.25.
FIG. 26-3 is a diagram showing a second embodiment, and is a third diagram showing the relationship between the total loss ratio and the carrier frequency when the rotation speed ratio of the motor is 0.25 in a graph format.
Mode for carrying out the invention
[0014]
　Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(
　First Embodiment) First, the first embodiment will be described.
　FIG. 1 is a diagram showing an example of a schematic configuration of a motor drive system.
　In the present embodiment, a case where the motor M is an IPMSM (Interior Permanent Magnet Synchronous Motor) in which a permanent magnet is built in a rotor is described as an example.
[0015]
　In FIG. 1, the motor drive system for driving such a motor M includes an AC power supply 10, a rectifier circuit 20, an electrolytic capacitor 30, a voltage sensor 40, an inverter 50, and current sensors 61 to 63. It has a control device 70 that controls the operation of the inverter 50.
[0016]
　The AC power supply 10 supplies AC power having a commercial frequency (50 Hz / 60 Hz).
　The rectifier circuit 20 is, for example, a full-wave rectifier circuit composed of four diodes, and converts AC power into DC power.
　The electrolytic capacitor 30 removes the pulsating current of the DC power output from the rectifier circuit 20.
[0017]
　The voltage sensor 40 measures the DC input voltage Vi input to the inverter 50.
　The inverter 50 is, for example, a circuit including six switching elements constituting a three-phase full bridge. The inverter 50 turns the switching element on and off based on the PWM signal S output from the control device 70 and input to the switching element, so that the input DC power has a frequency required to drive the motor M. It is converted into AC power having the above and output (supplied) to the motor M. In the present embodiment, a case where the switching element is a switching element configured by using a wide bandgap semiconductor (SiC, GaN, etc.) will be described as an example.
[0018]
　The current sensors 61 to 63 are, for example, CTs (Current Transformers), and measure the AC motor currents Iu, Iv, and Iw flowing in the windings of the respective phases u, v, and w of the motor M.
[0019]
　The control device 70 includes an applied voltage calculation unit 71, a carrier wave generation unit 72, a comparison unit 73, a PWM signal output unit 74, and a carrier frequency setting device 7A. The control device 70 can be realized by using, for example, a microcomputer or an arithmetic circuit. Further, the control device 70 can control the operation of the motor M by, for example, vector control. Since the configuration other than the configuration related to the carrier frequency can be realized by a known technique, detailed description thereof will be omitted here.
　The applied voltage calculation unit 71 measures the speed command value (command value of the rotation speed of the motor M) input from the outside, the torque command value (command value of the torque of the motor M) input from the outside, and the voltage sensor 40. The input voltage Vi and the motor currents Iu, Iv, and Iw measured by the current sensors 61 to 63 are input, and based on these, the voltage applied to each phase of the motor M is calculated and the voltage is shown. Generates a voltage command signal. The carrier frequency setting device 7A has a carrier frequency setting unit 75.
[0020]
　The carrier wave generation unit 72 generates a carrier wave (carrier wave used for generating the PWM signal S) in PWM control. In the present embodiment, a case where the carrier wave is a triangular wave will be described as an example.
　The comparison unit 73 compares the voltage command signal generated by the applied voltage calculation unit 71 with the triangular wave (carrier wave) generated by the carrier wave generation unit 72.
　The PWM signal output unit 74 outputs a pulse signal corresponding to the result of comparison in the comparison unit 73 to the inverter 50 as a PWM signal S. As described above, the inverter 50 turns on / off the switching element based on the PWM signal S, converts the input DC power into AC power, and outputs it to the motor M.
[0021]
　The carrier frequency setting unit 75 sets the carrier frequency (carrier frequency of the inverter 50), which is the frequency of the carrier wave. The carrier wave generation unit 72 generates a triangular wave having a carrier frequency set by the carrier frequency setting unit 75. In the present embodiment, the carrier frequency setting unit 75 sets the carrier frequency according to the command value of the rotation speed of the motor M and the command value of the torque of the motor M.
[0022]
　As explained in the section of the problem to be solved by the invention, in Patent Documents 2 and 3, the carrier frequency is increased when the motor torque is small (the carrier frequency is decreased when the motor torque is large). In some cases it is not desirable to do so. In order to demonstrate this, the present inventor has made a highly efficient motor drive system from the viewpoint of total high efficiency calculated from the total loss of the motor loss and the inverter loss as the total efficiency of the motor drive system. The carrier frequency was investigated. The results will be described below.
[0023]
　Here, the total efficiency of the motor drive system is a value obtained by dividing the output (= torque × rotation speed) of the motor M by the input power to the inverter 50 (total efficiency = output ÷ input power).
　The value obtained by subtracting the output of the motor M from the input power to the inverter 50 is the energy (loss) lost in the motor drive system. Here, the breakdown of the loss was examined assuming that this loss is equal to the sum of the loss of the motor M and the loss of the inverter 50. The loss of the motor M includes not only iron loss and copper loss, but also mechanical loss, wind loss, bearing loss and the like. However, if the shape of the motor M is the same and the rotation speed is the same, these losses (mechanical loss, wind loss, bearing loss, etc.) can be considered to be constant even if the operation of the inverter 50 is changed. .. Therefore, the iron loss shown below shall include these losses. Even in this way, if the number of revolutions is the same, the loss of the motor M includes a certain amount of these losses (mechanical loss, wind loss, bearing loss, etc.), but the torque of the motor M changes. However, it is considered that there is no problem in verifying the tendency of increase / decrease in the loss of the motor drive system. Therefore, here, it is assumed that the loss of the motor M consists of iron loss (however, loss including mechanical loss, wind loss, bearing loss, etc.) and copper loss. Further, here, the range of the carrier frequency is set to 5 kHz to 50 kHz.
[0024]
　As described above, in the present embodiment, the motor M to be evaluated is IPMSM. The basic specifications of the motor M are as follows. Further, as the semiconductor element constituting the switching element of the inverter 50, a SiC semiconductor element which is one of the wide bandgap semiconductor elements was used.
・ Number of phases; 3
・ Number of poles; 12
・ Stator outer diameter; 135 mm
・ Stator inner diameter; 87 mm
・ Stator slot number; 18 (concentrated winding)
・ Stator (core) material: Non-oriented electrical steel sheet (35A300) -Rotor
outer diameter: 85 mm
-Rotor (core) product thickness: 30 mm
-Residual magnetic flux density of permanent magnet in rotor 1.1T
[0025]
　FIGS. 2-1 to 2-2 are diagrams showing the measurement results of the loss when the rotation speed ratio of the motor M is 1.00 in a table format. The rotation speed ratio is the ratio of the rotation speed at the time of measurement to the maximum rotation speed of the motor M. The rotation speed ratio of 1.00 indicates that the measurement was performed at the same rotation speed as the maximum rotation speed. 2-1 (a), 2-1 (b), 2-1 (c), 2-2 (a), and 2-2 (b) have torque ratios of 0.05, respectively. The measurement results at the time of 0.125, 0.25, 0.375, 0.5 are shown. The torque ratio is the ratio of the torque at the time of measurement to the maximum torque of the motor M. A torque ratio of 0.5 indicates that the measurement was performed at a torque of 50% of the maximum torque. Here, the maximum rotation speed and the maximum torque of the motor M are appropriately designed and determined according to the application of the motor M.
[0026]
　In FIGS. 2-1 and 2-2, f c indicates a carrier frequency. Here, the ratio of the output power of the motor M to the input power of the inverter 50 is referred to as total efficiency. In Figure 2-1 and Figure 2-2, the overall efficiency is the highest, the torque ratio 0.5, the carrier frequency f c f of is when the 40 kHz (Fig. 2-2 (b) c = 40 kHz ). In Figure 2-1 and Figure 2-2, the overall efficiency ratio, to the maximum overall efficiency in the same rotational speed ratio, each carrier frequency f c is a ratio of overall efficiency in.
[0027]
　Further, the sum of the copper loss and iron loss of the motor M and the loss of the inverter 50 is referred to as a total loss. In Figure 2-1 and Figure 2-2, the overall loss ratio is the same carrier frequency f in the rotational speed ratio and the same torque ratio c Overall to loss, the carrier frequency when the minimum (5 kHz in this case) It is the ratio of the total loss at f c .
　Further, in FIGS. 2-1 and FIG. 2-2, the copper loss ratio, the carrier frequency f in the same rotational speed ratio and the same torque ratio c for total loss when the lowest (5 kHz in this case), the It is the ratio of the copper loss of the motor M at the carrier frequency f c . Iron loss ratio, the carrier frequency f in the same rotational speed ratio and the same torque ratio c for total loss when the lowest (5 kHz in this case), the carrier frequency f c the ratio of the iron loss of the motor M in Is. Inverter loss ratio, the carrier frequency f in the same rotational speed ratio and the same torque ratio c for total loss when the lowest (5 kHz in this case), the carrier frequency f c at a ratio of loss of the inverter 50 in is there.
　FIG. 3 is a graph showing the relationship between the total efficiency ratio and the carrier frequency shown in FIGS. 2-1 and 2-2 in a graph format.
[0028]
　As shown in FIGS. 2-1 and 2-2, and FIG. 3, under the condition that the torque ratio is relatively small (torque ratio is 0.05, 0.125), the total efficiency ratio is when the carrier frequency is 40 kHz. Became the largest. On the other hand, under the condition of the torque ratio of 0.25, the total efficiency ratio became the largest when the carrier frequency was 20 kHz. Under the condition that the torque ratio is larger (torque ratio is 0.375 and 0.5), the total efficiency ratio is the largest when the carrier frequencies are 30 kHz and 40 kHz, respectively, and the larger the torque ratio, the larger the total efficiency ratio. The carrier frequency becomes higher. In the following description, the carrier frequency that maximizes the total efficiency (minimum total loss) within the same torque ratio is referred to as the optimum carrier frequency, if necessary. In FIG. 2-2 (b), the total efficiency ratios when the carrier frequencies are 30 kHz and 40 kHz are both 1.000, but when calculated up to the fourth decimal place, the total efficiency when the carrier frequency is 40 kHz. The ratio (1.0000) was larger than the total efficiency ratio (0.9997) when the carrier frequency was 30 kHz.
[0029]
　As described above, when the rotation speed ratio of the motor M is 1.00, it can be seen that the optimum carrier frequency has a minimum value in relation to the optimum carrier frequency and the torque of the motor M. Further, it can be seen that there is only one torque range corresponding to the lowest carrier frequency (torque ratio 0.250 only). Then, in the range where the torque of the motor M is equal to or higher than the torque of the motor M corresponding to the lowest optimum carrier frequency, it can be seen that the optimum carrier frequency becomes the same or higher as the torque of the motor M increases. On the other hand, in the range where the torque of the motor M is equal to or less than the torque of the motor M corresponding to the lowest optimum carrier frequency, it can be seen that the optimum carrier frequency becomes the same or lower as the torque of the motor M increases. As described above, in the techniques described in Patent Documents 2 and 3, the carrier frequency is lowered as the torque of the motor M increases. On the other hand, the present inventor has a minimum value for the optimum carrier frequency in the relationship between the optimum carrier frequency derived for each motor rotation speed and the torque of the motor M, and corresponds to the lowest optimum carrier frequency. In the range above the torque of the motor M, when the torque of the motor M increases, the optimum carrier frequency must be the same or higher, and further, it is equal to or less than the torque of the motor M corresponding to the lowest optimum carrier frequency. For the first time, we have found that the overall efficiency of the motor drive system can be improved by making the carrier frequency the same or lower as the torque of the motor M increases.
[0030]
　Therefore, the present inventor has investigated a factor that can improve the efficiency of the motor drive system by increasing the carrier frequency under the condition that the torque of the motor M is large.
　4-1 and 4-2 are graphs showing the relationship between the total loss ratio and the carrier frequency shown in FIGS. 2-1 and 2-2 in a graph format. FIGS. 4-1 (a), 4-1 (b), 4-1 (c), 4-2 (a), and 4-2 (b) each have a torque ratio of 0.05. , 0.125, 0.25, 0.375, 0.5 (FIG. 2-1 (a), FIG. 2-1 (b), FIG. 2-1 (c), FIG. 2-2 (a), FIG. The result in the case of 2-2 (b)) is shown.
[0031]
　As shown in FIGS. 4-1 (a) and 4-1 (b), under the conditions where the torque ratios are 0.05 and 0.125 (hereinafter referred to as low load conditions), the iron of the motor M with respect to the total loss The loss ratio is large. Therefore, by increasing the carrier frequency, the iron loss of the motor M can be reduced. On the other hand, if the carrier frequency is increased, the loss of the inverter 50 increases. Further, the sum of the iron loss ratio and the copper loss ratio approaches a constant value while gradually decreasing as the carrier frequency increases. The carrier frequency that minimizes the total loss is determined by the balance between the decrease in the loss of the motor M and the increase in the loss of the inverter 50 as described above. Therefore, when the torque ratios are 0.05 and 0.125, it is considered that the optimum carrier frequency is 40 kHz.
[0032]
　Next, as shown in FIG. 4-1 (c), under the condition of the torque ratio of 0.25 (hereinafter referred to as the medium load condition), FIGS. 4-1 (a) and 4-2 (b) are shown. The ratio of the copper loss of the motor M to the total loss is larger than that under the low load condition shown. Further, as in the case of low load conditions, the sum of the iron loss ratio and the copper loss ratio gradually decreases and approaches a constant value as the carrier frequency increases, but the sum of the iron loss ratio and the copper loss ratio becomes The carrier frequency that becomes substantially constant is 20 kHz, which is lower than that under the low load condition. Further, as in the case of the low load condition, when the carrier frequency is increased, the loss of the inverter 50 becomes large. However, when the carrier frequency becomes 20 kHz or more, the amount of increase in the loss of the inverter 50 with respect to the increase in the carrier frequency becomes larger than in the low load condition (when the carrier frequency in 40 kHz or more) (how the loss of the inverter 50 increases). Suddenly). The carrier frequency at which the total loss is minimized is determined in consideration of the decrease in the loss of the motor M and the increase in the loss of the inverter 50 as described above, and the carrier frequency is lower than in the low load condition. Therefore, when the torque ratio is 0.25, it is considered that the optimum carrier frequency is 20 kHz.
[0033]
　Next, as shown in FIGS. 4-2 (a) and 4-2 (b), under the conditions where the torque ratios are 0.375 and 0.5 (hereinafter referred to as high load conditions), FIG. 4-1 The ratio of the copper loss of the motor M to the total loss is larger than that under the medium load condition shown in (c). Further, even under high load conditions, as in the case of low load conditions and medium load conditions, as the carrier frequency increases, the sum of the iron loss ratio and the copper loss ratio gradually decreases and approaches a constant value. , Inverter loss ratio increases. Further, the larger the torque of the motor M, the larger the inverter loss ratio at each carrier frequency.
[0034]
　As the torque of the motor M increases (that is, when the load becomes high), the motor current required to generate the torque increases. Therefore, a higher carrier frequency is required in order to control the waveform with high accuracy by PWM control. That is, under high load conditions, the copper loss of the motor M becomes larger than that under medium load conditions due to the increase in motor current, and under conditions where the carrier frequency is low, the waveform of the magnetic flux density is distorted and there are many harmonic components. Since it is generated, the iron loss of the motor M increases as compared with the medium load condition.
[0035]
　The carrier frequency that minimizes the total loss is determined by the balance between the decrease in the loss of the motor M and the increase in the loss of the inverter 50 as described above, and the carrier frequency is higher than that under the medium load condition. Further, the carrier frequency becomes higher as the torque of the motor M increases. Therefore, when the torque ratios are 0.375 and 0.5, it is considered that the optimum carrier frequencies are 30 kHz and 40 kHz, respectively.
[0036]
　As described above, when the rotation speed ratio of the motor M is 1.00, the torque of the motor M is large in the range where the torque of the motor M is equal to or less than the torque of the motor M corresponding to the lowest optimum carrier frequency. Then, the optimum carrier frequency is set to be the same or lower, and in the range where the torque of the motor M is equal to or higher than the torque of the motor M corresponding to the lowest optimum carrier frequency, the optimum carrier frequency becomes higher when the torque of the motor M increases. By making the same or higher, the efficiency of the entire motor drive system can be maximized (loss is minimized).
[0037]
　Next, the present inventor has a minimum value for the optimum carrier frequency in the relationship between the optimum carrier frequency and the torque of the motor M regardless of the rotation speed of the motor M, and corresponds to the lowest optimum carrier frequency. It was confirmed that it is necessary to make the optimum carrier frequency the same or higher as the torque of the motor M increases in the range of the torque of the motor M or more. This is shown in FIGS. 5-1 to 13-3. The contents of the items in the tables of FIGS. 5-1 to 5-3, 8-1 to 8-3, and 11-1 to 11-3 are shown in FIGS. 2-1 and 2-2. It is the same as the contents of the item.
[0038]
　In "Fig. 5-1 to Fig. 5-3", "Fig. 8-1 to Fig. 8-3", and "Fig. 11-1 to Fig. 11-3", the rotation speed ratio of the motor M is 0.75, respectively. It is a figure which shows the measurement result of the loss at the time of 0.50, 0.25 in a tabular form. "Fig. 5-1 (a), Fig. 8-1 (a), Fig. 11-1 (a)", "Fig. 5-1 (b), Fig. 8-1 (b), Fig. 11-1 (b)" , "Fig. 5-1 (c), Fig. 8-1 (c), Fig. 11-1 (c)", "Fig. 5-2 (a), Fig. 8-2 (a), Fig. 11-2 ( a) ”,“ Fig. 5-2 (b), Fig. 8-2 (b), Fig. 11-2 (b) ”,“ Fig. 5-2 (c), Fig. 8-2 (c), Fig. 11- 2 (c) ”,“ Fig. 5-3 (a), Fig. 8-3 (a), Fig. 11-3 (a) ”,“ Fig. 5-3 (b), Fig. 8-3 (b), Fig. "11-3 (b)" and "Fig. 5-3 (c), Fig. 8-3 (c), Fig. 11-3 (c)" have torque ratios of 0.05, 0.125, and 0, respectively. The measurement results at the time of 25, 0.375, 0.5, 0.625, 0.75, 0.875, 1.0 are shown. When the rotation speed ratio of the motor M was 0.75 or less, the torque of the motor M could be applied up to the maximum torque.
[0039]
　In addition, FIGS. 6, 9, and 12 show the total efficiency ratio and the carrier shown in FIGS. 5-1 to 5-3, 8-1 to 8-3, and 11-1 to 11-3, respectively. It is a figure which shows the relationship with a frequency in a graph format. FIG. 6B is an enlarged view of a region in which the total efficiency ratio of FIG. 6A is 0.980 to 1.005. FIG. 9B is an enlarged view of a region in which the total efficiency ratio of FIG. 9A is 0.95 to 1.01. FIG. 12B is an enlarged view of a region in which the total efficiency ratio of FIG. 12A is 0.90 to 1.00.
[0040]
　7-1 to 7-3, 10-1 to 10-3, and 13-1 to 13-3 are FIGS. 5-1 to 5-3 and 8-1 to 8, respectively. -3, is a graph showing the relationship between the total loss ratio shown in FIGS. 11-1 to 11-3 and the carrier frequency in a graph format. "Fig. 7-1 (a), Fig. 10-1 (a), Fig. 13-1 (a)", "Fig. 7-1 (b), Fig. 10-1 (b), Fig. 13-1 (b)" , "Fig. 7-1 (c), Fig. 10-1 (c), Fig. 13-1 (c)", "Fig. 7-2 (a), Fig. 10-2 (a), Fig. 13-2 ( a) ”,“ FIG. 7-2 (b), FIG. 10-2 (b), FIG. 13-2 (b) ”,“ FIG. 7-2 (c), FIG. 10-2 (c), FIG. 13- 2 (c) ”,“ FIG. 7-3 (a), FIG. 10-3 (a), FIG. 13-3 (a) ”,“ FIG. 7-3 (b), FIG. 10-3 (b), FIG. "13-3 (b)", "Fig. 7-3 (c), Fig. 10-3 (c), Fig. 13-3 (c)" have torque ratios of 0.05, 0.125, and 0, respectively. The results at the time of .25, 0.375, 0.5, 0.625, 0.75, 0.875.1.0 are shown.
[0041]
　As shown in FIGS. 5-1 to 13-3, when the rotation speed ratios of the motors M are 0.25, 0.50, and 0.75, the optimum carrier is also used as in the case of 1.00. Regarding the relationship between the frequency and the torque of the motor M, there is a minimum value for the optimum carrier frequency, and in the range where the torque of the motor M is equal to or greater than the torque of the motor M corresponding to the lowest optimum carrier frequency, the motor M It can be seen that as the torque increases, the optimum carrier frequency becomes the same or higher. In FIG. 5-2 (b), the total efficiency ratios when the carrier frequencies are 10 kHz and 15 kHz are both 0.999, but when calculated up to the fourth decimal place, the total efficiency when the carrier frequency is 10 kHz. The ratio was higher than the total efficiency ratio when the carrier frequency was 15 kHz. Further, in FIGS. 5-3 (b) and 5-3 (c), the total efficiency ratios when the carrier frequencies are 10 kHz and 15 kHz are 0.995 and 0.991, respectively, but when calculated up to the fourth decimal place, respectively. The total efficiency ratio when the carrier frequency is 15 kHz is larger than the total efficiency ratio when the carrier frequency is 10 kHz. Further, in FIGS. 8-1 (c) and 11-2 (c), the total efficiency ratios when the carrier frequencies are 5 kHz and 10 kHz are 0.977 and 0.983, respectively, but the fourth decimal place. When calculated up to that point, the total efficiency ratio when the carrier frequency was 10 kHz was larger than the total efficiency ratio when the carrier frequency was 5 kHz.
[0042]
　When the motor M rotation speed ratios are 0.25, 0.50, and 0.75, the carrier frequency is increased because the excitation basic frequency is lower than when the motor M rotation speed ratio is 1.00. As a result, the effect of reducing the sum of the copper loss ratio and the iron loss ratio becomes smaller (partly due to the influence of measurement variations, etc., the sum of the copper loss ratio and the iron loss ratio increases as the carrier frequency increases. ing). Therefore, when the rotation speed ratios of the motor M are 0.25, 0.50, and 0.75, the torque of the motor M is the lowest optimum as in the case where the rotation speed ratio of the motor M is 1.00. When there is no range smaller than the torque of the motor M corresponding to the carrier frequency and the torque of the motor M increases, the efficiency of the entire motor drive system is maximized (loss) by making the optimum carrier frequency the same or higher. Can be minimized).
[0043]
[table 1]

[0044]
　The above results are shown in Table 1. Table 1 shows the optimum carrier frequency for each torque ratio and motor M rotation speed ratio obtained from the results shown in FIGS. 2-1 to 13-2. Here, the case where the interval for changing the torque ratio is 0.125 (or 0.075) is shown as an example. The intervals for changing the torque ratio are as shown in FIGS. 2-1 to 2-2, 5-1 to 5-3, 8-1 to 8-3, and 11-1 to 11-3. If it is also reduced, the optimum carrier frequency may increase or decrease (slightly) even in the range of torque ratios in which the optimum carrier frequencies are the same in Table 1 due to measurement variations and the like. For example, when the rotation speed ratio of the motor is 0.25, the optimum carrier frequency is 5 kHz in the range of the torque ratio of 0.05 to 0.125, but the torque ratio is between 0.05 and 0.125. The optimum carrier frequency may increase or decrease with respect to 5 kHz. Therefore, in the above description, in order to maximize the overall efficiency of the motor drive system, in the range of the torque ratio derived from the relationship that the optimum carrier frequency is the same value even if the torque of the motor M changes. , It is not necessary to set the carrier frequency to be completely the same as the optimum carrier frequency, and it is sufficient that the carrier frequency is substantially the same.
　A difference of about 5% of the carrier frequency has a small effect on the value of the optimum carrier frequency that minimizes the total loss. Therefore, "substantially equivalent" in the present specification means "the difference in carrier frequency is 5% or less".
[0045]
　As is clear from Table 1, the relationship between the torque of the motor M and the optimum carrier frequency is that the optimum carrier frequency increases as the torque of the motor M increases, regardless of the rotation speed ratio of the motor M. Has a part. For example, when the rotation speed ratio of the motor M is 0.75, the optimum carrier frequency changes from 5 kHz to 10 kHz when the torque ratio changes from 0.125 to 0.250 and the torque of the motor M increases. It gets higher. Further, when the torque ratio changes from 0.625 to 0.750 and the torque of the motor M increases, the optimum carrier frequency changes from 10 kHz to 15 kHz, which increases. Further, when the rotation speed ratio of the motor M is 1.00, the torque ratio changes from 0.250 to 0.375 and 0.375 to 0.500, and when the torque of the motor M increases, the optimum carrier frequency Is higher because it changes from 20 kHz to 30 kHz and from 30 kHz to 40 kHz, respectively. Further, when the rotation speed ratio of the motor M is 1.00, the optimum carrier frequency becomes lower as the torque of the motor M increases. Specifically, when the torque ratio changes from 0.125 to 0.250 and the torque of the motor M increases, the optimum carrier frequency changes from 40 kHz to 20 kHz, and thus decreases.
　Further, it can be seen that there is only one range of the torque ratio corresponding to the optimum carrier frequency of the lowest value regardless of the rotation speed ratio of the motor M. For example, when the rotation speed ratio of the motor M is 0.75, the optimum carrier frequency is the lowest value of 5 kHz in the range of the torque ratio of 0.05 to 0.125, and is optimal in the range of other torque ratios. The value of the carrier frequency is higher than 5 kHz. When the rotation speed ratio of the motor M is 1.00, the optimum carrier frequency is the lowest value of 20 kHz at a torque ratio of 0.250, and the value of the optimum carrier frequency is 20 kHz in the range of other torque ratios. Higher than. Therefore, in the range where the torque ratio of the motor M is smaller than the range of the torque ratio corresponding to the lowest optimum carrier frequency, the optimum carrier frequency becomes the same or lower as the torque ratio of the motor M increases. Or, in the range where the torque ratio of the motor M is larger than the range of the torque ratio corresponding to the lowest optimum carrier frequency, the optimum carrier frequency is the same or higher as the torque ratio of the motor M increases. As a result, the efficiency of the entire motor drive system can be maximized (loss can be minimized).
[0046]
　In other IPMSMs and inverters 50, the present inventor maximizes the efficiency of the entire motor drive system by making the optimum carrier frequency substantially equal to or higher when the torque of the motor M increases ( It was confirmed that there is a torque range that can minimize the loss).
　Further, the value of the sum of the inverter loss ratio, the iron loss ratio, and the copper loss ratio itself differs depending on the type of the inverter or the motor M, but the inverter loss ratio, the iron loss ratio, and the copper loss ratio with respect to the change in the carrier frequency It is considered that the behavior of the change with the sum does not differ significantly depending on the type of the motor M. Therefore, when the torque of the motor M is increased, the efficiency of the entire motor drive system can be maximized (loss is minimized) by making the carrier frequencies substantially equal to or higher than those of the IPMSM. Not limited to this, it is considered that the same applies to other types of motors M.
[0047]
　As described above, the carrier frequency setting unit 75 sets the carrier frequency according to the command value of the rotation speed of the motor M and the command value of the torque of the motor M. Therefore, the relationship between the rotation speed and torque of the motor M and the optimum carrier frequency is stored in advance. An example of a method of deriving the relationship between the torque of the motor M and the optimum carrier frequency for each rotation speed of the motor M will be described with reference to the flowchart of FIG. The flowchart of FIG. 14 is an example of a preparatory process performed before the motor M is used in an actual machine (for example, a train, a hybrid vehicle, a home electric appliance, etc.).
[0048]
　First, in step S1401, the control device 70 designates one unselected candidate from the plurality of candidates for the rotation speed of the motor M preset for the control device 70.
　Next, in step S1402, the control device 70 designates one unselected candidate from the plurality of candidates for the torque of the motor M preset for the control device 70.
[0049]
　Next, in step S1403, the control device 70 designates one unselected candidate from the plurality of candidates for the carrier frequency preset for the control device 70.
　Next, in step S1404, the control device 70 generates a PWM signal S based on the contents specified in steps S1401 to S1403 and outputs the PWM signal S to the inverter 50. The inverter 50 operates the motor M based on the PWM signal S. At this time, the applied voltage calculation unit 71 uses the rotation speed specified in step S1401 as the command value of the rotation speed of the motor M and the torque specified in step S1402 as the command value of the torque of the motor M, respectively. The voltage applied to the phase is calculated, and a voltage command signal indicating the voltage is generated. Further, the carrier wave generation unit 72 generates a triangular wave having a carrier frequency specified in step S1403.
[0050]
　Next, in step S1405, the total loss when the motor M is operated in step S1404 (total loss when the motor M is driven by using the inverter 50) is measured. As described above, the total loss is the sum of the copper loss and iron loss of the motor M and the loss of the inverter 50. The total loss is derived as a value obtained by subtracting the output of the motor M from the input power to the inverter 50. The copper loss of the motor M is derived as a Joule loss from the current flowing through the windings of each of the phases u, v, and w of the motor M and the winding resistance. The iron loss of the motor M is derived as a value obtained by subtracting the output of the motor M and the copper loss from the input power to the motor M. The loss of the inverter 50 is derived as a value obtained by subtracting the output power of the inverter (input power to the motor M) from the input power to the inverter 50.
　Next, in step S1406, the control device 70 determines whether or not all of the plurality of candidates for the carrier frequency preset for the control device 70 have been designated. As a result of this determination, if all the plurality of candidates for the carrier frequency are not specified, the process returns to step S1403. Then, the processes of steps S1403 to S1406 are repeatedly executed until all of the plurality of candidates for the carrier frequency are specified. That is, the measurement (derivation) of the total loss in step S1405 is performed with different carrier frequencies in the inverter 50.
[0051]
　When it is determined in step S1406 that all of the plurality of carrier frequency candidates have been specified, the rotation speed specified in step S1401 and the number of rotations specified in step S1402 are specified using the triangular waves of all the carrier frequency candidates. The total loss when the motor M is driven by generating the PWM signal S with the generated torque as the command value is obtained in the repeatedly executed step S1405. Then, the process proceeds to step S1407.
　In step S1407, the control device 70 drives the motor M by generating a PWM signal S whose command values ​​are the rotation speed of the motor M specified in step S1401 and the torque of the motor M specified in step S1402. The carrier frequency that is the smallest total loss among the total losses in the case is specified as the optimum carrier frequency (that is, the carrier frequency when the total loss is minimized is the optimum carrier frequency based on the total loss derived in step S1405). Derived as).
[0052]
　At this time, the optimum carrier frequency may be specified as follows. At the stage where the process proceeds to step S1407, the number of pairs of the carrier frequency candidates specified in step S1403 and the total loss measured in step S1405 when the carrier frequency is specified is obtained by the number of carrier frequency candidates. Has been done. The control device 70 derives an equation showing the relationship between the carrier frequency and the total loss by a known method such as the least squares method, based on the pair of the carrier frequency candidate and the total loss. In this equation, the control device 70 specifies the carrier frequency that minimizes the total loss as the optimum carrier frequency.
[0053]
　Next, in step S1408, the control device 70 determines whether or not all of the plurality of candidates for the torque of the motor M preset for the control device 70 are designated. As a result of this determination, if all the plurality of candidates for the torque of the motor M are not specified, the process returns to step S1402. Then, the processes of steps S1402 to S1408 are repeatedly executed until all of the plurality of candidates for the torque of the motor M are specified. That is, the measurement (derivation) of the total loss in step S1405 is performed by making the torque generated in the motor M different. Further, the optimum carrier frequency is derived in step S1407 for each of the plurality of torques.
　When it is determined in step S1408 that all the plurality of candidates for the torque of the motor M are specified, the rotation speed of the motor M specified in step S1401 and the rotation speed of the motor M specified in step S1401 are used by using the triangular waves of all the candidates of the carrier frequency. The optimum carrier frequency when the motor M is driven by generating the PWM signal S with each of all the torque candidates of the motor M as a command value is obtained in the repeatedly executed step S1407. Then, the process proceeds to step S1409.
[0054]
　In step S1409, the control device 70 derives the relationship between the torque of the motor M and the optimum carrier frequency with respect to the rotation speed of the motor M specified in step S1401. A specific example of a method for deriving the relationship between the torque of the motor M and the optimum carrier frequency will be described. First, the control device 70 extracts the optimum carrier frequency in the torque of the motor M specified in step S1402 for each of the torques of the motor M specified in step S1402 which is repeatedly executed. As a result, for the rotation speed of the motor M specified in step S1401, a set of the torque of the motor M and the optimum carrier frequency in the torque of the motor M is obtained for the number of candidates for the torque of the motor M. The control device 70 derives a set of the torque of the motor M obtained as described above and the optimum carrier frequency in the torque of the motor M as the relationship between the torque of the motor M and the optimum carrier frequency.
[0055]
　Next, in step S1410, the control device 70 determines whether or not all of the plurality of candidates for the rotation speed of the motor M preset for the control device 70 are designated. As a result of this determination, if all the plurality of candidates for the rotation speed of the motor M are not specified, the process returns to step S1401. Then, the processes of steps S1401 to S1410 are repeatedly executed until all of the plurality of candidates for the rotation speed of the motor M are specified. That is, the measurement (derivation) of the total loss in step S1405 is performed at different rotation speeds of the motor M. Further, the derivation of the optimum carrier frequency in step S1407 is performed for each of the plurality of rotation speeds.
　When it is determined in step S1410 that all the plurality of candidates for the rotation speed of the motor M are specified, the relationship between the torque of the motor M and the optimum carrier frequency is determined for each of the candidates for the rotation speed of the motor M. Obtained in step S1409, which was repeatedly executed. Then, the process proceeds to step S1411.
[0056]
　In step S1411, the control device 70 derives and stores the relationship between the torque of the motor M and the optimum carrier frequency for each rotation speed of the motor M based on the optimum carrier frequency derived in step S1407. This relationship is as shown in Table 1.
[0057]
　At this time, based on the findings explained with reference to Table 1, the relationship between the torque of the motor M derived for each rotation speed of the motor M by the control device 70 and the optimum carrier frequency (relationship derived in step S1411) is , The torque of the motor M is a plurality of optimum carrier frequencies specified in step S1407 (a plurality of optimum carriers specified under the condition that the rotation speed of the motor M is common and the torque of the motor M is different from each other). In the range where the torque of the motor M corresponding to the lowest optimum carrier frequency of the frequency) is equal to or higher than the torque of the motor M, the carrier frequency becomes higher as the torque of the motor M becomes larger (first part).
[0058]
　In the example shown in Table 1, when the rotation speed ratios of the motor M are 0.25, 0.50, 0.75, and 1.00, the minimum optimum carrier frequencies are 5 kHz, 5 kHz, 5 kHz, and 20 kHz, respectively. The torque ratios corresponding to the lowest optimum carrier frequency are 0.050 and 0.125, 0.050 and 0.125, 0.050 and 0.125, and 0.250, respectively. When the rotation speed ratio of the motor M is 0.25, 0.50, 0.75, 1.00, the torque ratio is in the range of 0.125, which is equal to or higher than the torque ratio corresponding to the lowest optimum carrier frequency. In the range of ~ 0.250, 0.125 to 0.250, 0.125 to 0.250, and 0.250 to 0.500, the torque ratios are 0.125 to 0.250 and 0.125, respectively. From 0.250, 0.125 to 0.250, 0.250 to 0.375 and 0.375 to 0.500, the optimum carrier frequencies are 5 to 10, 5 to 10, respectively. It changes from 5 to 10, 20 to 30 and 30 to 40, respectively, and becomes higher. The relationship between the torque of the motor M and the optimum carrier frequency derived for each rotation speed of the motor M by the control device 70 is such a relationship.
[0059]
　In the example in which the rotation speed ratio of the motor M in Table 1 is "0.25", the relationship derived in step S1411 is that the torque ratio of the motor M is the plurality of rotation speed ratios of the motor M derived in step S1407. The optimum carrier frequency ("5", "" corresponding to the rotation speed ratio "0.25" of one of ("0.25", "0.50", "0.75", "1.00")). Of the 10 "), it is optimal when the torque ratio of the motor M becomes large in the range where the torque ratio of the motor M corresponding to the lowest carrier frequency" 5 "is equal to or higher than ("0.050 "," 0.125 "). It has a first portion (a portion where the torque ratio of the motor M is 0.050 or more and 1.000 or less) in which the carrier frequency becomes high.
　The "first portion in which the optimum carrier frequency increases as the torque ratio of the motor M increases" may include "a portion in which the optimum carrier frequency is substantially the same even when the torque ratio of the motor M increases". ..
　In the example in which the rotation speed ratio of the motor M in Table 1 is "0.25", the "torque ratio of the motor M is 0.050 or more and 1.000 or less" in the first portion (the torque ratio of the motor M is 0.050 or more and 1.000 or less). The part where the optimum carrier frequency is substantially the same even if it increases (the part where the torque ratio of the motor M is 0.050 or more and 0.125 or less, and the part where the torque ratio of the motor M is 0.250 or more and 1.000 or less. Part) ”is included.
[0060]
　In the example in which the rotation speed ratio of the motor M in Table 1 is "0.50", the relationship derived in step S1411 is that the torque ratio of the motor M is the optimum carrier frequency ("5", "5" derived in step S1407. 10 ”), it is optimal when the torque ratio of the motor M becomes large in the range where the torque ratio of the motor M corresponding to the lowest carrier frequency“ 5 ”(“ 0.050 ”,“ 0.125 ”) or more. It has a first portion (a portion where the torque ratio of the motor M is 0.050 or more and 1.000 or less) in which the carrier frequency becomes high.
　In the example in which the rotation speed ratio of the motor M in Table 1 is "0.50", the "torque ratio of the motor M is 0.050 or more and 1.000 or less" in the first part (the torque ratio of the motor M is 0.050 or more and 1.000 or less). Parts where the optimum carrier frequency is substantially the same even if it increases (the torque ratio of the motor M is 0.050 or more and 0.125 or less, and the torque ratio of the motor M is 0.250 or more and 1.000 or less. Part) ”is included.
[0061]
　In the example in which the rotation speed ratio of the motor M in Table 1 is "0.75", the relationship derived in step S1411 is that the torque ratio of the motor M is the optimum carrier frequency ("5", "5" derived in step S1407. Of 10 ”and“ 15 ”), the torque ratio of the motor M is within the range of the torque ratio of the motor M (“0.050”, “0.125”) corresponding to the lowest carrier frequency “5”. When it becomes large, it has a first portion (a portion where the torque ratio of the motor M is 0.050 or more and 0.750 or less) in which the optimum carrier frequency becomes high.
　In the example in which the rotation speed ratio of the motor M in Table 1 is "0.75", the "torque ratio of the motor M is 0.050 or more and 0.750 or less" in the first portion (the torque ratio of the motor M is 0.050 or more and 0.750 or less). The part where the optimum carrier frequency is substantially the same even if it becomes large (the part where the torque ratio of the motor M is 0.050 or more and 0.125 or less, and the part where the torque ratio of the motor M is 0.250 or more and 0.625 or less. Part) ”is included.
[0062]
　In the example where the rotation speed ratio of the motor M in Table 1 is "1.00", the relationship derived in step S1411 is that the torque ratio of the motor M is the optimum carrier frequency ("20", "20" derived in step S1407. Among 30 ”and“ 40 ”), when the torque ratio of the motor M increases in the range of the torque ratio (“0.250”) of the motor M corresponding to the lowest carrier frequency “20”, the optimum carrier frequency Has a first portion (a portion where the torque ratio of the motor M is 0.250 or more and 0.500 or less).
[0063]
　Further, when the torque of the motor M is equal to or less than the torque of the motor M corresponding to the lowest optimum carrier frequency among the plurality of optimum carrier frequencies specified as described above, the control device is in the range. The relationship between the torque of the motor M derived for each rotation speed of the motor M by 70 and the optimum carrier frequency has a portion (second portion) in which the carrier frequency decreases as the torque of the motor M increases.
[0064]
　In the example shown in Table 1, when the rotation speed ratio of the motor M is 1.00, the minimum optimum carrier frequency is 20 kHz, the torque ratio corresponding to the minimum optimum carrier frequency is 0.250, and the torque is the same. There are torque ratios (= 0.250, 0.125, 0.050) equal to or less than the ratio (= 0.250). Then, in the range of 0.125 to 0.250, which is the range of the torque ratio of 0.250 or less, which is the torque ratio corresponding to the lowest optimum carrier frequency, the torque ratio changes from 0.125 to 0.250. As the frequency increases, the optimum carrier frequency changes from 40 to 20, and decreases. The relationship between the torque of the motor M derived by the control device 70 and the optimum carrier frequency is such a relationship.
[0065]
　In the example where the rotation speed ratio of the motor M in Table 1 is "1.00", the relationship derived in step S1411 is that the torque ratio of the motor M is the optimum carrier frequency ("20", "20" derived in step S1407. Among 30 ”and“ 40 ”), when the torque ratio of the motor M increases within the range of the torque ratio (“0.250”) of the motor M corresponding to the lowest carrier frequency “20”, the optimum carrier frequency Has a second portion (a portion where the torque ratio of the motor M is 0.050 or more and 0.250 or less).
　The "second portion in which the optimum carrier frequency decreases as the torque ratio of the motor M increases" may include "a portion in which the optimum carrier frequency is substantially the same even when the torque ratio of the motor M increases". ..
　In the example where the rotation speed ratio of the motor M in Table 1 is "1.00", the "torque ratio of the motor M is 0.050 or more and 0.250 or less" in the second part (the torque ratio of the motor M is 0.050 or more and 0.250 or less). A portion where the optimum carrier frequency is substantially the same even if the value is increased (a portion where the torque ratio of the motor M is 0.050 or more and 0.125 or less) ”is included.
[0066]
　For example, the control device 70 has a relationship between the torque of the motor M and the optimum carrier frequency for each of the candidates for the rotation speed of the motor M (a set of the torque of the motor M and the optimum carrier frequency of the motor M). Therefore, a table for correlating and storing the motor M rotation speed, the motor M torque, and the optimum carrier frequency can be derived for each motor M rotation speed as the relationship between the motor M torque and the optimum carrier frequency. it can. Further, the control device 70 has a relationship between the torque of the motor M and the optimum carrier frequency for each of the candidates for the rotation speed of the motor M (a set of the torque of the motor M and the optimum carrier frequency of the motor M). Therefore, an equation showing the relationship between the torque of the motor M and the optimum carrier frequency can be derived for each rotation speed of the motor M by a known method such as the minimum square method. Then, the process according to the flowchart of FIG. 14 is completed.
[0067]
　According to the flowchart of FIG. 14, after the relationship between the torque of the motor M and the optimum carrier frequency is stored for each rotation speed of the motor M (after the preparation process is completed), the relationship between the torque of the motor M and the optimum carrier frequency is stored. An actual use step of driving the motor M in the actual machine is carried out by using each rotation speed of the motor M. In the actual use process, for example, the following processing is executed.
　When driving the motor M, the carrier frequency setting unit 75 commands the torque command value of the motor M and the rotation speed of the motor M from the relationship between the torque of the motor M and the optimum carrier frequency for each rotation speed of the motor M. The optimum carrier frequency corresponding to the value is extracted as the carrier frequency in the inverter 50 (that is, the carrier frequency is set according to the command value of the torque of the motor M and the command value of the rotation speed of the motor M based on the above-mentioned relationship. To do).
　For example, when the carrier frequency in the inverter 50 is set from the relationship between the torque ratio of the motor M and the optimum carrier frequency at the rotation speed ratio 1.00 of the motor M shown in Table 1, the carrier frequency setting unit 75 of the motor M is used. In the range where the torque is equal to or higher than the torque of the motor M corresponding to the lowest optimum carrier frequency (20 kHz) (the torque ratio of the motor M is in the range of 0.250 to 0.500), when the torque of the motor M increases, the torque is 20 kHz to 40 kHz. The optimum carrier frequency that becomes higher is set as the carrier frequency in the inverter 50. Further, the carrier frequency setting unit 75 has a range in which the torque of the motor M is equal to or less than the torque of the motor M corresponding to the minimum optimum carrier frequency (20 kHz) (the torque ratio of the motor M is in the range of 0.050 to 0.250). The optimum carrier frequency, which decreases from 40 kHz to 20 kHz as the torque of the motor M increases, is set as the carrier frequency in the inverter 50.
[0068]
　When the relationship is used as a table, the table may not have the same value as the command value (rotation speed of the motor M, torque). In this case, the carrier frequency setting unit 75 performs interpolation processing or extrapolation processing on the values ​​stored in the table based on the command value, so that the same value as the command value (of the motor M). The optimum carrier frequency corresponding to (rotation speed, torque) can be derived as the carrier frequency in the inverter 50.
　The carrier wave generation unit 72 generates a triangular wave having a carrier frequency set by the carrier frequency setting unit 75 in this way. As described above, the value of the optimum carrier frequency in the relationship between the torque of the motor M and the optimum carrier frequency for each rotation speed of the motor M is used as the carrier frequency applied to the inverter 50. Therefore, the relationship between the torque of the motor M and the optimum carrier frequency for each rotation speed of the motor M is synonymous with the relationship between the torque of the motor M and the carrier frequency applied to the inverter 50 for each rotation speed of the motor M.
[0069]
　As described above, in the present embodiment, when the inverter 50 having the switching element configured by using the wide band gap semiconductor is used as the inverter 50, the torque of the motor M is equal to or more than the torque at which the optimum carrier frequency becomes the minimum. In the region, the relationship between the torque of the motor M and the optimum carrier frequency is determined for each rotation speed of the motor M so that the optimum carrier frequency becomes substantially the same or higher as the torque of the motor M increases. Therefore, the carrier frequency can be set so as to increase the efficiency of the entire motor drive system in consideration of the iron loss and copper loss of the motor M and the switching loss in the inverter 50. Therefore, the motor M can be driven so that the total loss of the loss of the motor M and the loss of the inverter 50 becomes small.
[0070]
　In this embodiment, the relationship between the torque of the motor M and the optimum carrier frequency has been described by taking as an example a case where the relationship between the torque of the motor M and the optimum carrier frequency is derived for each rotation speed of the motor M by performing actual measurement. However, the relationship between the motor torque and the optimum carrier frequency does not necessarily have to be derived for each rotation speed of the motor M in this way. For example, the total loss of the motor drive system when the motor M is excited by the inverter 50 may be derived by using numerical analysis.
[0071]
　Further, in the present embodiment, the relationship between the torque of the motor M and the optimum carrier frequency has been described by taking as an example a case where the control device 70 derives the relationship for each rotation speed of the motor M. However, the relationship between the torque of the motor M and the optimum carrier frequency may be derived for each rotation speed of the motor M by an information processing device different from the control device 70. For example, this is preferable when the total loss of the motor drive system when the motor M is excited by the inverter 50 is derived by using numerical analysis. Further, in this case, the control device 70 acquires the relationship between the torque of the motor M and the optimum carrier frequency derived for each rotation speed of the motor M in the information processing device. At this time, the relationship between the torque of the motor M and the optimum carrier frequency may be stored inside the control device 70 for each rotation speed of the motor M, or outside the control device 70 for each rotation speed of the motor M. It may be remembered.
[0072]
　Further, in the present embodiment, the case where the input power to the inverter 50 is generated by using the AC power supply 10 and the rectifier circuit 20 has been described as an example. However, it is not always necessary to do this. For example, a DC power supply can be used as an alternative to the AC power supply 10 and the rectifier circuit 20. Further, the DC power supply may have a buck-boost function. Alternatively, the DC power supply has a power storage function and may be configured to store the regenerative power from the motor M.
[0073]
(Second Embodiment)
　Next, the second embodiment will be described. In the first embodiment, the case where the switching element constituting the inverter 50 is a switching element configured by using a wide bandgap semiconductor has been described as an example. On the other hand, in the present embodiment, the case where the switching element constituting the inverter 50 is a switching element configured by using a semiconductor other than the wide bandgap semiconductor (semiconductor having a general bandgap) will be described. As described above, the present embodiment and the first embodiment are mainly different in configuration due to the difference in the switching elements constituting the inverter 50. Therefore, in the description of the present embodiment, detailed description of the same parts as those of the first embodiment will be omitted by adding the same reference numerals as those given in FIGS. 1 to 14.
[0074]
　The present inventor uses a Si semiconductor element, which is one of the semiconductors having a general bandgap, as the semiconductor element constituting the switching element of the inverter 50, and sets the carrier frequency range to 5 kHz to 40 kHz. Others investigated the carrier frequency for obtaining a highly efficient motor drive system under the same conditions as described in the first embodiment. The results will be described below.
　15-1 to 15-2 are diagrams showing the measurement results of the loss when the rotation speed ratio of the motor M is 1.00 in a table format. 15-1 (a), (b), 15-2 (a), (b) are shown in FIGS. 2-1 (a), (b), 2-2 (a), (b), respectively. It is a figure corresponding to. FIG. 16 is a graph showing the relationship between the total efficiency ratio and the carrier frequency shown in FIGS. 15-1 and 15-2 in a graph format. FIG. 16 is a diagram corresponding to FIG. 17-1 and 17-2 are graphs showing the relationship between the total loss ratio and the carrier frequency shown in FIGS. 15-1 and 15-2 in a graph format. 17-1 (a), (b), (c), 17-2 (a), (b) are shown in FIGS. 4-1 (a), (b), (c), and FIG. 4-, respectively. It is a figure corresponding to 2 (a), (b).
[0075]
　18-1 to 18-3, 21-1 to 21-3, and 24-1 to 24-3 show that the rotation speed ratios of the motors M are 0.75, 0.50, and 0, respectively. It is a figure which shows the measurement result of the loss at the time of 25 in a tabular form. 18-1 (a), (b), (c) to 18-3 (a), (b), (c), FIG. 21-1 (a), (b), (c) to 21 -3 (a), (b), (c), FIG. 24-1 (a), (b), (c) to FIGS. 24-3 (a), (b), (c) are shown in FIGS. 5-1 (a), (b), (c) to 5-3 (a), (b), (c), 8-1 (a), (b), (c) to 8- 3 (a), (b), (c), FIGS. 11-1 (a), (b), (c) to 11-3 (a), (b), (c). ..
[0076]
　19, FIG. 22, and FIG. 25 show the total efficiency ratio and the carrier frequency shown in FIGS. 18-1 to 18-3, 21-1 to 21-3, and 24-1 to 24-3, respectively. It is a figure which shows the relationship of.
　20-1 to 20-3, 23-1 to 23-3, and 26-1 to 26-3 are FIGS. 18-1 to 18-3 and 21-1 to 21, respectively. -3, is a graph showing the relationship between the total loss ratio shown in FIGS. 24-1 to 24-3 and the carrier frequency in a graph format. 20-1 (a), (b), (c) to 20-3 (a), (b), (c), FIG. 23-1 (a), (b), (c) to 23. -3 (a), (b), (c), FIGS. 26-1 (a), (b), (c) to 26-3 (a), (b), (c) are shown in FIGS. 7-1 (a), (b), (c) -Fig. 7-3 (a), (b), (c), Fig. 10-1 (a), (b), (c) -Fig. 10- 3 (a), (b), (c), FIGS. 13-1 (a), (b), (c) to 13-3 (a), (b), (c). ..
[0077]
　As shown in FIGS. 17-1 to 17-2, 20-1 to 20-3, 23-1 to 23-3, and 26-1 to 26-3, the switching element of the inverter 50. When a wide bandgap semiconductor is used as the above (FIGS. 4-1 to 4-2, 7-1 to 7-3, 10-1 to 10-3, and 13-1 to 13-3. ), The inverter loss ratio is larger. This is because the switching loss of the switching element is smaller when the wide bandgap semiconductor is used as the switching element than when a general semiconductor other than the wide bandgap semiconductor is used as the switching element. This switching loss tends to increase as the carrier frequency increases.
[0078]
　Further, as shown in FIGS. 16, 19, 22, and 25, the optimum carrier frequency becomes 5 kHz even if the rotation speed ratio and the torque ratio of the motor M are changed. Even if a semiconductor other than the wide bandgap semiconductor is used as the switching element, as described in the first embodiment, in the region where the carrier frequency is low, the sum of the iron loss ratio and the copper loss ratio gradually increases as the carrier frequency increases. After that, it approaches a certain value. On the other hand, as described above, when a semiconductor other than the wideband gap semiconductor is used as the switching element, the loss (and the inverter loss ratio) of the inverter 50 becomes larger than that when the wideband gap semiconductor is used as the switching element, and further. The amount of increase in the loss (and inverter loss ratio) of the inverter 50 with respect to the increase in carrier frequency also increases (the loss (and inverter loss ratio) of the inverter 50 increases rapidly).
　From the above, when a semiconductor other than the wide bandgap semiconductor is used as the switching element, the optimum carrier frequency becomes substantially the same regardless of the rotation speed and torque of the motor M.
[0079]
　As described in the first embodiment, the intervals for changing the torque ratio are shown in FIGS. 15-1 to 15-2, 18-1 to 18-3, 21-1 to 21-3, and so on. If the interval is smaller than the interval shown in FIGS. 24-1 to 24-3, the optimum carrier frequency may increase or decrease due to variations in measurement or the like. Therefore, it is not necessary to make the optimum carrier frequencies completely the same, but they may be made substantially the same.
　As described above, when the present inventor uses a general semiconductor other than the wide bandgap semiconductor as the switching element of the inverter 50, the optimum carrier frequency is determined regardless of the rotation speed and torque of the motor M. For the first time, I found the finding that they are almost equivalent. Further, as described in the first embodiment, it was confirmed that the efficiency of the entire motor drive system can be maximized (loss can be minimized) by doing the same for the other motor M and the inverter 50.
[0080]
　Further, the above optimum carrier frequency can be derived, for example, by performing the processes of steps S1401 to S1408 and S1410 in the flowchart of FIG. When the optimum carrier frequency differs (slightly) depending on the torque of the motor M, the motor has a representative value (for example, average value, most frequent value, median value, minimum value, or maximum value) as the optimum carrier frequency. One may be derived for each rotation speed of M, or as described in the flowchart of FIG. 14, the relationship between the torque of the motor M and the optimum carrier frequency (optimal regardless of the torque and rotation speed of the motor M). The relationship that the carrier frequencies have substantially the same value) may be derived for each rotation speed of the motor M. In any of the derivation methods, the carrier frequency set for each rotation speed of the motor M by the carrier frequency setting unit 75 is substantially the same value (for example, the lowest optimum carrier frequency) regardless of the rotation speed and torque of the motor M. The value is almost the same as the value).
　That is, in the present embodiment, in the actual use process, the carrier frequency setting unit 75 sets the optimum carrier frequency to the inverter based on the relationship that the optimum carrier frequency becomes substantially the same value regardless of the torque and the rotation speed of the motor M. The carrier frequency at 50 is set for each rotation speed of the motor M.
[0081]
　As described above, in the present embodiment, when the inverter 50 having a switching element configured by using a semiconductor other than the wide bandgap semiconductor is used as the inverter 50, the carrier frequency is abbreviated regardless of the rotation speed and torque of the motor M. Make it equivalent. Therefore, even if a switching element configured by using a general semiconductor other than the wide bandgap semiconductor is used, the same effect as described in the first embodiment can be obtained.
　Also in this embodiment, various modifications described in the first embodiment can be adopted.
　The above-mentioned value of the rotation speed ratio of the motor M is only an example, and the present invention can be applied to a value other than the above-mentioned value of the rotation speed ratio of the motor M.
[0082]
　The configuration of the control device 70 in the embodiment of the present invention described above can be realized by executing a program by a computer. Further, a computer-readable recording medium on which the program is recorded and a computer program product such as the program can also be applied as an embodiment of the present invention. As the recording medium, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a magnetic tape, a non-volatile memory card, a ROM, or the like can be used.
　In addition, the embodiments of the present invention described above are merely examples of embodiment of the present invention, and the technical scope of the present invention should not be construed in a limited manner by these. It is a thing. That is, the present invention can be implemented in various forms without departing from the technical idea or its main features.
Description of the sign
[0083]
　10: AC power supply, 20: Rectifier circuit, 30: Electrolytic capacitor, 40: Voltage sensor, 50: Inverter, 61-63: Current sensor, 70: Control device, 71: Applied voltage calculation unit, 72: Carrier wave generator, 73: Comparison unit, 74: PWM signal output unit, 75: Carrier frequency setting unit
The scope of the claims
[Claim 1]
　A carrier frequency setting method for setting a carrier frequency in an inverter for driving a motor,
　which is a total loss which is the sum of the loss of the inverter and the loss of the motor when the motor is driven by the inverter. Is derived based on the loss derivation step in which the torque generated in the motor, the rotation speed of the motor, and the carrier frequency in the inverter are made different from each other, and the
　total loss derived by the loss derivation step. , The
　carrier frequency derivation step of deriving the carrier frequency at the time when the total loss is minimized as the optimum carrier frequency in each of the combination of the plurality of motors and the plurality of rotation speeds, and the optimum carrier frequency deriving step derived by the carrier frequency deriving step. A relationship derivation step of deriving the relationship between the motor torque and the optimum carrier frequency based on the carrier frequency for
　each rotation speed of the motor, and a relationship derived for each rotation speed of the motor by the relationship deriving step. And
　the carrier frequency corresponding to the command value of the torque of the motor and the command value of the rotation speed of the motor when the motor is driven after the relationship is memorized by the relationship storage step. , A carrier frequency setting step for setting based on the relationship,
　and a carrier frequency setting method.
[Claim 2]
　The inverter has a switching element configured by using a wide band gap semiconductor,
　and the relationship between the torque of the motor and the optimum carrier frequency derived for each rotation speed of the motor in the relationship derivation step is as described above. When the torque of the motor increases in the range where the torque of the motor is equal to or higher than the torque of the motor corresponding to the lowest carrier frequency among the optimum carrier frequencies derived by the carrier frequency derivation step, the optimum carrier frequency The carrier frequency setting method according to claim 1, wherein the carrier frequency setting method has a first portion in which the frequency is increased.
[Claim 3]
　The relationship between the torque of the motor and the optimum carrier frequency derived for each rotation speed of the motor in the relationship derivation step is that the torque of the motor is among the optimum carrier frequencies derived in the carrier frequency derivation step. The carrier according to claim 2, wherein the carrier has a second portion in which the optimum carrier frequency becomes lower when the torque of the motor becomes larger in the range of the torque of the motor corresponding to the lowest carrier frequency. Frequency setting method.
[Claim 4]
　The relationship between the torque of the motor and the optimum carrier frequency derived for each rotation speed of the motor in the relationship derivation step is that the torque of the motor is derived from the carrier frequency derivation step of the motor. The carrier frequency setting method according to claim 2 or 3, wherein the motor has only one torque range corresponding to the lowest carrier frequency among the frequencies.
[Claim 5]
　The inverter has a switching element configured by using a semiconductor other than a wideband gap semiconductor,
　and the relationship between the torque of the motor and the optimum carrier frequency derived for each rotation speed of the motor in the relationship derivation step. The carrier frequency setting method according to claim 1, wherein the optimum carrier frequency has substantially the same value regardless of the torque of the motor.
[Claim 6]
　A motor drive system including an inverter, a motor driven by receiving AC power from the inverter, and a control device for controlling the operation of the
　inverter. The inverter is configured by using a wide band gap semiconductor. The
　controller has a switching element, and the control device sets a carrier frequency of the inverter based on the relationship between the torque of the motor derived for each rotation speed of the motor and the carrier frequency of the inverter.
　The relationship between the torque of the motor and the carrier frequency , which has a setting means and is derived for each rotation speed of the motor, is characterized by having a portion in which the carrier frequency increases as the torque of the motor increases. Drive system.
[Claim 7]
　The relationship between the torque of the motor and the carrier frequency derived for each rotation speed of the motor corresponds to the lowest carrier frequency of the portion where the torque of the motor increases as the torque of the motor increases. The motor drive system according to claim 6, wherein the motor drive system has a portion in which the carrier frequency becomes lower when the torque of the motor becomes larger in the range of being equal to or less than the torque of the motor.
[Claim 8]
　A motor drive system including an inverter, a motor driven by receiving AC power from the inverter, and a control device for controlling the operation of the
　inverter. The inverter is a semiconductor other than a wideband gap semiconductor. The
　control device has a switching element configured in use, and the control device sets the carrier frequency of the inverter based on the relationship between the torque of the motor derived for each rotation speed of the motor and the carrier frequency in the inverter. a carrier frequency setting unit that,
　the relationship between the torque and the carrier frequency of the motor is derived for each rotation speed of the motor, regardless of the torque of the motor, the carrier frequency is substantially equal to the value Characterized motor drive system.
[Claim 9]
　A carrier frequency setting device for setting a carrier frequency of an inverter for driving a motor,
　wherein the carrier frequency setting device uses
　the torque of the motor and the motor of the inverter when the motor is driven by the motor. As a relationship with the optimum carrier frequency, which is the carrier frequency when the total loss, which is the sum of the loss and the loss of the motor, is minimized, the
　inverter has a switching element configured by using a wide band gap semiconductor. In addition, in the range where the torque of the motor is equal to or greater than the torque of the motor corresponding to the carrier frequency at which the optimum carrier frequency is the lowest value, when the torque of the motor increases, the optimum carrier frequency increases. Then, in the range where the torque of the motor is equal to or less than the torque of the motor corresponding to the carrier frequency at which the optimum carrier frequency becomes the lowest value, when the torque of the motor increases, the portion where the optimum carrier frequency becomes lower is further increased. The relationship to be obtained is derived for each rotation speed of the motor, and when the
　inverter has the switching element configured by using a semiconductor other than the wide band gap semiconductor, the optimum A relationship in which the carrier frequency is a substantially constant value is derived for each rotation speed of the
　motor, and the carrier frequency of the inverter is set based on the relationship between the torque of the motor and the optimum carrier frequency. Carrier frequency setting device.