FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
DRIVING SYSTEM
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED AND
EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3,
MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
2
5 DESCRIPTION
Technical Field
[0001] The present disclosure relates to a drive system.
Background Art
10 [0002] Some drive systems installed in electric railway vehicles convert DC power
fed from a substation via an overhead wire into desired AC power and feed the AC power
to motors to drive the motors to generate propulsive force of the electric railway vehicles.
Because of the limited space under the floor of the railway vehicle, such a drive system
preferably includes a small number of motors to generate propulsive force for allowing
15 the railway vehicle to run at a target speed.
[0003] Some of the drive systems employ synchronous motors having a higher
efficiency than induction motors as the motors. A typical example of this type of drive
system is disclosed in Patent Literature 1. The electric vehicle control device disclosed
in Patent Literature 1 includes permanent-magnet synchronous motors, inverters
20 associated with the respective permanent-magnet synchronous motors on a one-to-one
basis, and gate controllers for controlling the inverters.
Citation List
Patent Literature
[0004] Patent Literature 1: Unexamined Japanese Patent Application Publication
25 No. 2012-075317
Summary of Invention
Technical Problem
[0005] In an exemplary case where an inverter stops due to a short-circuit fault in
the inverter under no loads, the permanent-magnet synchronous motor unintentionally
30 generates a no-load induced voltage proportional to the rotational speed of the motor
because of the permanent magnet. In the electric vehicle control device disclosed in
3
5 Patent Literature 1, this phenomenon causes a current to flow from the permanent-magnet
synchronous motor to the inverter when the inverter stops. This current resulting from
the no-load induced voltage and flowing from the permanent-magnet synchronous motor
to the inverter can cause a failure. In order to avoid such a failure, the electric vehicle
control device disclosed in Patent Literature 1 is also provided with contactors between
10 the inverters and the permanent-magnet synchronous motors.
[0006] The electric vehicle control device disclosed in Patent Literature 1 requires
contactors of which the number is equal to the number of permanent-magnet synchronous
motors, and thus inevitably has a more complicated structure and a larger size. This
problem can occur not only in drive systems fed with electric power from overhead wires
15 but also in drive systems for driving permanent-magnet synchronous motors by means of
electric power fed from power sources.
[0007] An objective of the present disclosure, which has been accomplished in
view of the above situations, is to provide a drive system having a simple structure.
Solution to Problem
20 [0008] In order to achieve the above objective, a drive system according to an
aspect of the present disclosure includes a reluctance motor, a converter, and a controller.
The reluctance motor rotates in response to feeding of electric power. The power
converter includes multiple switching elements and is connected directly to the reluctance
motor. The power converter converts electric power fed from a power source into
25 electric power to be fed to the reluctance motor and feeds the converted electric power to
the reluctance motor. The controller controls the switching elements included in the
power converter.
Advantageous Effects of Invention
[0009] In the drive system according to an aspect of the present disclosure, the
30 power converter is connected directly to the reluctance motor. The drive system does
not require a contactor between the power converter and the reluctance motor and
4
5 therefore has a simplified structure.
Brief Description of Drawings
[0010] FIG. 1 is a block diagram illustrating a drive system according to an
embodiment;
FIG. 2 is a block diagram illustrating a controller according to the embodiment;
10 FIG. 3 is a block diagram illustrating a gate signal generator according to the
embodiment;
FIG. 4 is a block diagram illustrating a drive system according to a first
modification of the embodiment; and
FIG. 5 is a block diagram illustrating a drive system according to a second
15 modification of the embodiment.
Description of Embodiments
[0011] A drive system according to an embodiment of the present disclosure is
described in detail below with reference to the accompanying drawings. In the
drawings, the components identical or corresponding to each other are provided with the
20 same reference symbol.
[0012] The following description is directed to a drive system 1 according to an
embodiment, focusing on an exemplary drive system for generating propulsive force of a
railway vehicle. The drive system 1 illustrated in FIG. 1 is installed under the floor of
the railway vehicle, for example. The drive system 1, for example, converts DC power
25 into three-phase AC power, feeds the three-phase AC power to a motor, and thus drives
the motor, thereby generating propulsive force of the railway vehicle.
[0013] The drive system 1 includes a terminal 1a connected to a power source, a
terminal 1b that is grounded, a filter capacitor FC1 to be charged with DC power fed
from the power source, and a power converter 11, which is a DC/AC three-phase
30 converter to convert the DC power fed from the power source via the filter capacitor FC1
into three-phase AC power. The drive system 1 further includes a motor M1, which is a
5
5 reluctance motor to rotate in response to feeding of the three-phase AC power from the
power converter 11, current sensors CT11, CT12, and CT13 to measure values of phase
currents flowing to the motor M1, and a controller 12 to control switching elements
SW11, SW12, SW13, SW14, SW15, and SW16 included in the power converter 11.
[0014] The power converter 11 is connected directly to the motor M1. This direct
10 connection means the connection of components without an active element therebetween.
Specifically, the power converter 11 is connected to the motor M1 without a switching
circuit therebetween, which serves to electrically disconnect the motor M1 from the
power converter 11. Examples of the switching circuit include electromagnetic
contactors, semiconductor switches, and mechanical switches to be manually operated.
15 Since the power converter 11 is connected directly to the motor M1, the drive system 1
has a simpler structure than that of a drive system provided with a contactor between a
power converter and a permanent-magnet synchronous motor.
[0015] The individual components of the drive system 1 are described in detail
below.
20 The terminal 1a is electrically connected to the power source, which is not
illustrated. A typical example of the power source is a current collector to acquire
electric power from a power supply line. The power supply line is an overhead wire or
a third rail, for example. The current collector is a pantograph or a contact shoe, for
example. The terminal 1a is preferably electrically connected to the current collector via
25 a device, such as contactor or filter reactor. The terminal 1b is grounded via a wheel.
[0016] The filter capacitor FC1 has one end electrically connected to the terminal
1a, and the other end electrically connected to the terminal 1b. The filter capacitor FC1
constitutes a filter together with the filter reactor, which is provided between the terminal
1a and the current collector as described above, and thereby reduces harmonic
30 components.
[0017] The power converter 11 is an inverter to convert DC power into three-phase
6
5 AC power, for example, an inverter capable of variable voltage variable frequency
control. The power converter 11 according to the embodiment includes the switching
elements SW11 and SW12 connected to a U-phase coil of the motor M1, the switching
elements SW13 and SW14 connected to a V-phase coil of the motor M1, and the
switching elements SW15 and SW16 connected to a W-phase coil of the motor M1.
10 The power converter 11 also includes freewheeling diodes D11, D12, D13, D14, D15,
and D16 connected in parallel to the respective switching elements SW11, SW12, SW13,
SW14, SW15, and SW16.
[0018] The switching elements SW11 and SW12 are connected in series to each
other, the switching elements SW13 and SW14 are connected in series to each other, and
15 the switching elements SW15 and SW16 are connected in series to each other. The
point of connection between the switching elements SW11 and SW12 is connected
directly to the U-phase coil of the motor M1. The point of connection between the
switching elements SW13 and SW14 is connected directly to the V-phase coil of the
motor M1. The point of connection between the switching elements SW15 and SW16
20 is connected directly to the W-phase coil of the motor M1. The serially connected
switching elements SW11 and SW12, the serially connected switching elements SW13
and SW14, and the serially connected switching elements SW15 and SW16 are
connected in parallel to one another.
[0019] The switching elements SW11, SW12, SW13, SW14, SW15, and SW16 are
25 switched between on and off states by the controller 12. The power converter 11 thus
converts the DC power fed from the power source via the filter capacitor FC1 into
three-phase AC power to be fed to the motor M1. The power converter 11 then feeds
the three-phase AC power to the motor M1. For example, the switching elements
SW11, SW12, SW13, SW14, SW15, and SW16 are insulated gate bipolar transistors
30 (IGBTs).
[0020] The motor M1 to be fed with the three-phase AC power from the power
7
5 converter 11 is a reluctance motor, and thus has a low power factor and requires a
reactive current. A conceivable solution is expansion of the volume of the power
converter 11, but the power converter 11 having an expanded volume inevitably has an
increased size.
In order to reduce the iron loss in the motor M1, the power converter 11 needs to
10 execute high-frequency switching. In the case where the switching elements SW11,
SW12, SW13, SW14, SW15, and SW16 are semiconductor devices made of silicon, the
high-frequency switching generates increased amounts of heat, and requires a larger
cooling device for cooling the switching elements SW11, SW12, SW13, SW14, SW15,
and SW16.
15 [0021] Existing railway vehicles do not include reluctance motors because a vehicle
control apparatus including a large power converter and a large cooling device cannot be
readily installed in the limited space under the floor or on the roof of a railway vehicle.
In this embodiment, wide-gap semiconductors are employed as the switching elements
SW11, SW12, SW13, SW14, SW15, and SW16 included in the power converter 11.
20 This configuration can achieve expansion of the volume of the power converter 11 and
execution of high-frequency switching while maintaining the sufficiently small size of the
power converter 11, and allow a reluctance motor to be employed as the motor M1. The
wide-gap semiconductors are made of a material, such as silicon carbide, gallium nitride
material, or diamond, having a larger bandgap than silicon.
25 [0022] The anodes of the freewheeling diodes D11, D12, D13, D14, D15, and D16
are respectively connected to the emitters of the switching elements SW11, SW12, SW13,
SW14, SW15, and SW16, and the cathodes are respectively connected to the collectors of
the switching elements SW11, SW12, SW13, SW14, SW15, and SW16. This circuitry
suppress an inverse current from flowing to the switching elements SW11, SW12, SW13,
30 SW14, SW15, and SW16.
[0023] The motor M1 is a reluctance motor to rotate in response to feeding of
8
5 three-phase AC power from the power converter 11. The motor M1 according to the
embodiment is a synchronous reluctance motor including no permanent magnet. The
motor M1 lacks a permanent magnet and thus is free from a no-load induced voltage.
This configuration therefore does not require a contactor between the power converter 11
and the motor M1 for electrically disconnecting the motor M1 from the power converter
10 11 in order to suppress a current from flowing from the motor M1 to the power converter
11 when the power converter 11 stops. In other words, the configuration allows the
power converter 11 to be connected directly to the motor M1.
[0024] The current sensors CT11, CT12, and CT13 measure values of phase
currents flowing to the motor M1 and output the measured current values to the controller
15 12. For example, the current sensors CT11, CT12, and CT13 are current transformer
(CT) sensors.
In detail, the current sensor CT11 is provided to a bus bar that connects the point of
connection between the switching elements SW11 and SW12 to the U-phase coil of the
motor M1, and measures a value of U-phase current flowing from the power converter 11
20 to the motor M1. The current sensor CT12 is provided to a bus bar that connects the
point of connection between the switching elements SW13 and SW14 to the V-phase coil
of the motor M1, and measures a value of V-phase current flowing from the power
converter 11 to the motor M1. The current sensor CT13 is provided to a bus bar that
connects the point of connection between the switching elements SW15 and SW16 to the
25 W-phase coil of the motor M1, and measures a value of W-phase current flowing from
the power converter 11 to the motor M1.
[0025] The controller 12 generates gate signals S1 for controlling the switching
elements SW11, SW12, SW13, SW14, SW15, and SW16, on the basis of a torque
command value τ*
in accordance with an operation at a master controller installed in a
30 cab, which is not illustrated, of the railway vehicle, and the measured current values
acquired from the current sensors CT11, CT12, and CT13. The controller 12 then
9
5 outputs the generated gate signals S1.
[0026] As illustrated in FIG. 2, the controller 12 includes a current command
calculator 21 to calculate current command values from the torque command value τ
*
, a
voltage command calculator 22 to calculate voltage command values from the current
command values, and a rotating coordinate inverse transformer 23 to execute coordinate
10 transformation of the voltage command values. The controller 12 further includes a
position estimator 24 to estimate a position of the magnetic pole of the rotor included in
the motor M1, a rotating coordinate transformer 25 to execute coordinate transformation
of the measured current values, and a gate signal generator 26 to generate gate signals S1.
[0027] The current command calculator 21 calculates current command values i*
d
and i*
15 q in the rotating coordinate for achieving the target torque of the motor M1 indicated
by the torque command value τ
*
. For example, the current command values i*
d and i*
q
provide the minimum current effective value relative to the torque, that is, the minimum
copper loss of the motor M1.
The voltage command calculator 22 calculates voltage command values v*
d and v*
q
in the rotating coordinate, by obtaining the proportional integral of the differences (i*
20 d-id)
and (i*
q-iq) between the current command values i*
d and i*
q calculated by the current
command calculator 21 and the measured current values id and iq generated by the
rotating coordinate transformer 25.
[0028] The rotating coordinate inverse transformer 23 converts the voltage
command values v*
d and v*
q in the rotating coordinate into voltage command values v*
25 α
and v*
β in the two-phase coordinate, on the basis of a transformation matrix containing an
estimated position θ^, that is, a position of the magnetic pole of the rotor included in the
motor M1 estimated by the position estimator 24. The rotating coordinate inverse
transformer 23 then converts the voltage command values v*
α and v*
β in the two-phase
coordinate into voltage command values v*
u, v
*
v, and v*
30 w in the three-phase coordinate,
on the basis of a two-phase/three-phase transformation matrix.
10
5 [0029] The position estimator 24 estimates a position of the magnetic pole of the
rotor included in the motor M1, on the basis of the measured current values iu, iv, and iw
acquired from the current sensors CT11, CT12, and CT13, and the voltage command
values v*
u, v
*
v, and v*
w in the three-phase coordinate calculated by the rotating coordinate
inverse transformer 23. The estimated position θ^, that is, the position of the magnetic
10 pole of the rotor estimated by the position estimator 24 is represented in terms of
electrical angle.
[0030] The rotating coordinate transformer 25 converts the measured current values
iu, iv, and iw in the three-phase coordinate into measured current values iα and iβ in the
two-phase coordinate, on the basis of a three-phase/two-phase transformation matrix.
15 The rotating coordinate transformer 25 then converts the measured current values iα and
iβ in the two-phase coordinate into measured current values id and iq in the rotating
coordinate, on the basis of a transformation matrix containing the estimated position θ^.
[0031] The gate signal generator 26 generates gate signals S1 through pulse width
modulation (PWM) control. In detail, as illustrated in FIG. 3, the gate signal generator
20 26 includes a modulated wave generator 31 to generate modulated waves in accordance
with the voltage command values v*
u, v
*
v, and v*
w, a differentiator 32 to calculate a
rotational speed ω^ of the motor M1 through differentiation of the estimated position θ^,
a carrier wave generator 33 to generate a carrier wave in accordance with the rotational
speed ω^ of the motor M1, and a comparator 34 to generate gate signals on the basis of
25 comparison between the modulated waves and the carrier wave.
[0032] The modulated wave generator 31 generates modulated waves on the basis
of the voltage command values v*
u, v
*
v, and v*
w in the three-phase coordinate acquired
from the rotating coordinate inverse transformer 23. The modulated waves are signals
obtained through standardization of the voltage command values v*
u, v
*
v, and v*
w using
30 the value of the voltage between the terminals of the filter capacitor FC1.
The differentiator 32 calculates a rotational speed ω^ of the motor M1 through
11
5 differentiation of the estimated position θ^.
[0033] The carrier wave generator 33 generates a carrier wave in accordance with
the rotational speed ω^ of the motor M1 calculated by the differentiator 32. The
frequency of the carrier wave increases in accordance with acceleration of the rotational
speed of the motor M1. In other words, the frequency of the carrier wave has a positive
10 correlation with the rotational speed of the motor M1. The carrier wave generator 33
according to the embodiment generates a carrier wave, which is a signal obtained by
multiplying the frequency of the modulated waves. The operation mode of the gate
signal generator 26, in the case where the carrier wave is synchronized with the
modulated waves and is a signal obtained by multiplying the frequency of the modulated
15 waves, is defined as a synchronous multiple pulse mode. For example, when the gate
signal generator 26 operates in the synchronous multiple pulse mode, the carrier wave
generator 33 generates a carrier wave of which the frequency is 15 times higher than the
frequency of the modulated waves.
[0034] The comparator 34 generates gate signals S1 on the basis of comparison
20 between the modulated waves generated by the modulated wave generator 31 and the
carrier wave generated by the carrier wave generator 33, and outputs the generated gate
signals S1 to the switching elements SW11, SW12, SW13, SW14, SW15, and SW16.
In detail, the gate signals S1 for the switching elements SW11, SW13, and SW15 are at a
high (H) level when the value of the modulated waves is equal to or higher than the value
25 of the carrier wave, and at a low (L) level when the value of the modulated waves is
lower than the value of the carrier wave. The gate signals S1 for the switching elements
SW12, SW14, and SW16 are at an L level when the value of the modulated waves is
equal to or higher than the value of the carrier wave, and at an H level when the value of
the modulated waves is lower than the value of the carrier wave.
30 [0035] The switching elements SW11, SW12, SW13, SW14, SW15, and SW16 are
switched between on and off states in accordance with the gate signals S1 output from the
12
5 comparator 34. The gate signal generator 26 operating in the synchronous multiple
pulse mode can reduce the distortion of currents flowing to the motor M1 and allow the
motor M1 to function with high efficiency.
[0036] As described above, the motor M1 included in the drive system 1 according
to the embodiment is a synchronous reluctance motor including no permanent magnet
10 and thus is free from a no-load induced voltage. The drive system 1 therefore does not
require a contactor for electrically disconnecting the motor M1 from the power converter
11 in the case of stop of the inverter due to a short-circuit fault in the inverter, for
example, and allows the power converter 11 to be connected directly to the motor M1.
The drive system 1 according to the embodiment does not need a contactor and thus has a
15 simpler structure than that of a drive system provided with a contactor between a power
converter and a motor.
[0037] The above-described examples are not to be construed as limiting the
present disclosure. The drive system 1 may include multiple power converters 11 and
multiple motors M1. Because the power converters 11 and the motors M1 need to be
20 associated with each other on a one-to-one basis, the number of power converters 11 is
equal to the number of motors M1 in the drive system 1.
[0038] For example, FIG. 4 illustrates a drive system 2 including two power
converters 11 and 13, two motors M1 and M2, and two filter capacitors FC1 and FC2 to
be charged with electric power fed from a power source, which is not illustrated. The
25 power converters 11 and 13 have the identical configuration. The motors M1 and M2
have the identical configuration. The filter capacitors FC1 and FC2 have the identical
configuration. The drive system 2 also includes current sensors CT11, CT12, and CT13
to measure values of phase currents flowing to the motor M1, current sensors CT21,
CT22, and CT23 to measure values of phase currents flowing to the motor M2, and a
30 controller 12 to control multiple switching elements included in each of the power
converters 11 and 13.
13
5 [0039] The filter capacitors FC1 and FC2 are connected to the power source so as
to be in parallel to each other. In detail, the filter capacitor FC1 has one end connected
to the terminal 1a, and the other end connected to the terminal 1b. The filter capacitor
FC2 has one end connected to the terminal 1a, and the other end connected to the
terminal 1b. The filter capacitors FC1 and FC2 are charged with electric power fed
10 from the power source.
[0040] As in the above-described embodiment, the current sensors CT11, CT12,
and CT13 measure values of phase currents flowing to the motor M1 and output the
measured current values to the controller 12. The current sensors CT21, CT22, and
CT23 measure values of phase currents flowing to the motor M2 and output the measured
15 current values to the controller 12. The current sensors CT21, CT22, and CT23 are
provided to the respective bus bars that connect the power converter 13 to the motor M2,
like the current sensors CT11, CT12, and CT13.
[0041] The controller 12 generates gate signals S1 for controlling the switching
elements included in the power converter 11, on the basis of a torque command value τ
*
20 indicating a target torque of the motor M1 and the current values measured by the current
sensors CT11, CT12, and CT13, and then outputs the generated gate signals S1, as in the
above-described embodiment. The controller 12 also generates gate signals S2 for
controlling the switching elements included in the power converter 13, on the basis of a
torque command value τ
*
indicating a target torque of the motor M2 and the current
25 values measured by the current sensors CT21, CT22, and CT23, and then outputs the
generated gate signals S2. The gate signals S1 and S2 are generated in the same manner
as in the embodiment.
[0042] In the drive system 2 including the motors M1 and M2, the power converter
11 is connected directly to the motor M1, and the power converter 13 is connected
30 directly to the motor M2. The drive system 2 therefore has a simpler structure than that
of a drive system provided with contactors between power converters and motors.
14
5 [0043] Although the drive system 2 includes the filter capacitors FC1 and FC2 of
which the number is equal to the number of power converters 11 and 13 in the example
illustrated in FIG. 4, the power converters 11 and 13 may also be connected to a single
filter capacitor in common. FIG. 5 illustrates a drive system 3 that includes a filter
capacitor FC1 alone. The drive system 3 differs from the drive system 2 in that the
10 power converters 11 and 13 are connected to the filter capacitor FC1 in common.
[0044] The drive systems 1 to 3 do not necessarily include all of the current sensors
CT11, CT12, and CT13 and may include only two of the current sensors CT11, CT12,
and CT13. For example, the drive systems 1 to 3 may cause the current sensors CT11
and CT12 to measure values of U-phase and V-phase currents flowing to the motor M1
15 and calculate a value of W-phase current from the measured values of U-phase and
V-phase currents. In this case, the controller 12 generates gate signals S1 on the basis of
the measured values of U-phase and V-phase currents and the calculated value of
W-phase current.
[0045] The drive systems 2 and 3 may include any number of power converters 11
20 and 13 and any number of motors M1 and M2, provided that the number of power
converters is equal to the number of motors.
The drive systems 2 and 3 may include two controllers 12 independent from each
other. In this case, one of the controllers 12 controls the power converter 11, and the
other controller 12 controls the power converter 13.
25 [0046] Although the direct connection means the connection of components
without an active element therebetween in the above-described embodiment, the power
converter 11 and the motor M1 may also be connected to each other with none of an
active element and a passive element therebetween. The same holds true for the
connection between the power converter 13 and the motor M2.
30 [0047] The scope of the direct connection between the power converter 11 and the
motor M1 encompasses the connections via a component, such as relay terminal or relay
15
5 cable. In an exemplary case where the power converter 11 and the motor M1 are
installed in mutually different vehicle bodies, the power converter 11 and the motor M1
are connected to each other via a relay terminal. The same holds true for the direct
connection between the power converter 13 and the motor M2.
[0048] The carrier wave and the modulated waves are not necessarily synchronized
10 with each other. The mode, in the case where the carrier wave is not synchronized with
the modulated waves and have a frequency higher than the frequency of the modulated
waves, is defined as an asynchronous multiple pulse mode. The gate signal generator
26 operating in the asynchronous multiple pulse mode can reduce the distortion of
currents flowing to the motor M1 and allow the motor M1 to function with high
15 efficiency, as in the case of the synchronous multiple pulse mode.
[0049] The frequency of the carrier wave may be equal to the frequency of the
modulated waves in the case of a low rotational speed of the motor M1.
[0050] The controller 12 may acquire a measured value from a position sensor for
measuring a position of the magnetic pole of the rotor included in the motor M1, and
20 generate gate signals S1 in accordance with the value measured by the position sensor.
In this case, the gate signal generator 26 lacks the position estimator 24 and generates
gate signals S1 in accordance with the value measured by the position sensor.
[0051] The motor M1 may also be a switched reluctance motor, for example,
provided that the motor M1 includes no permanent magnet.
25 [0052] The switching elements SW11, SW12, SW13, SW14, SW15, and SW16
may be semiconductor devices made of silicon, and the freewheeling diodes D11, D12,
D13, D14, D15, and D16 may be wide-gap semiconductors.
[0053] The drive systems 1 to 3 are not necessarily installed under the floors of
railway vehicles and may also be installed at any site. For example, the drive systems 1
30 to 3 may be installed on the roofs of railway vehicles.
The drive systems 1 to 3 may be installed not only in railway vehicles of a DC
16
5 feeding system but also in railway vehicles of an AC feeding system. Any of the drive
systems 1 to 3 installed in a railway vehicle of an AC feeding system is fed with electric
power, which is subject to voltage reduction at a transformer and conversion at a
converter from AC power into DC power.
[0054] The drive systems 1 to 3 may be installed in railway vehicles other than
10 electric railway vehicles. For example, any of the drive systems 1 to 3 may be installed
in a diesel vehicle and fed with electric power from a generator driven by an internal
combustion engine to generate electric power. For another example, any of the drive
systems 1 to 3 may be installed in a rechargeable battery vehicle and fed with electric
power from a rechargeable battery.
15 The drive systems 1 to 3 may be installed in any moving body, such as automobile,
marine vessel, or aircraft, other than the railway vehicles.
[0055] The foregoing describes some example embodiments for explanatory
purposes. Although the foregoing discussion has presented specific embodiments,
persons skilled in the art will recognize that changes may be made in form and detail
20 without departing from the broader spirit and scope of the invention. Accordingly, the
specification and drawings are to be regarded in an illustrative rather than a restrictive
sense. This detailed description, therefore, is not to be taken in a limiting sense, and the
scope of the invention is defined only by the included claims, along with the full range of
equivalents to which such claims are entitled.
25 Reference Signs List
[0056] 1, 2, 3Drive system
1a, 1bTerminal
11, 13Power converter
12 Controller
30 21 Current command calculator
22 Voltage command calculator
17
5 23 Rotating coordinate inverse transformer
24 Position estimator
25 Rotating coordinate estimator
26 Gate signal generator
31 Modulated wave generator
10 32 Differentiator
33 Carrier wave generator
34 Comparator
CT11, CT12, CT13, CT21, CT22, CT23 Current sensor
D11, D12, D13, D14, D15, D16 Freewheeling diode
15 FC1, FC2 Filter capacitor
M1, M2 Motor
S1, S2 Gate signal
SW11, SW12, SW13, SW14, SW15, SW16 Switching element

5 WE CLAIM:
1. A drive system, comprising:
a reluctance motor to rotate in response to feeding of electric power;
a power converter comprising switching elements and connected directly to the
reluctance motor, the power converter being configured to convert electric power fed
10 from a power source into electric power to be fed to the reluctance motor and feed the
converted electric power to the reluctance motor; and
a controller to control the switching elements included in the power converter.
2. The drive system according to claim 1, wherein the switching elements
15 comprise wide-gap semiconductors.
3. The drive system according to claim 1, further comprising:
freewheeling diodes each connected in parallel to a corresponding one of the
switching elements, wherein
20 at least either of the switching elements or the freewheeling diodes comprise
wide-gap semiconductors.
4. The drive system according to any one of claims 1 to 3, wherein the
controller generates gate signals for the switching elements, on a basis of comparison
25 between modulated waves and a carrier wave, the modulated waves being associated
with voltage command values for achieving a target torque of the reluctance motor, the
carrier wave having a frequency increasing in accordance with acceleration of a rotational
speed of the reluctance motor.
19
5 5. The drive system according to any one of claims 1 to 4, wherein the
controller generates gate signals for the switching elements in accordance with a position
of a magnetic pole of a rotor included in the reluctance motor.
6. The drive system according to any one of claims 1 to 5, wherein
the power converter comprises a plurality of power converters,
10 the reluctance motor comprises a plurality of reluctance motors, a number of
which is equal to a number of the plurality of power converters, and
the plurality of power converters is connected directly to the plurality of
respective reluctance motors on a one-to-one basis.
15 7. The drive system according to claim 6, further comprising:
a filter capacitor to be charged with electric power fed from the power source,
wherein
the plurality of power converters is connected to the filter capacitor in common.
20 8. The drive system according to claim 6, further comprising:
a plurality of filter capacitors, a number of which is equal to the number of the
plurality of power converters, the plurality of filter capacitors being configured to be
charged with electric power fed from the power source, wherein
the plurality of filter capacitors is connected to the plurality of respective power
25 converters on a one-to-one basis.