FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
MOTOR DRIVING DEVICE AND AIR CONDITIONER
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.
Description
Technical Field
[0001]
The present invention relates to a motor driving device
and an air conditioner.
Background Art
[0002]
In controlling a motor, an inverter is used. There is a known technique of controlling multiple motors with a single inverter. For example, Patent Literature 1 describes an electric device that drives a first motor having multiple phases and a second motor having the same number of phases as the first motor with a single inverter circuit on the
basis of single-mode PWM control in a state where the phases
of the first motor and the phases of the second motor are connected to common output lines for the respective phases. Citation List
Patent Literature
[0003]
Patent Literature 1: Japanese Patent No. 4305021
Summary of Invention
Technical Problem
[0004]
In air conditioners in which multiple outdoor fan
motors are installed, it is common to change the number of driven fan motors depending on the air conditioning load.
This is to change the number of driven outdoor fan motors depending on the air conditioning load, and for example,
when the air conditioning load is low, only one of the outdoor fan motors is driven, and when the air conditioning
load is high, the number of driven outdoor fan motors is
increased.
[0005]
Thus, in a case where the number of driven outdoor fan
motors is increased, when an outdoor fan motor that is
rotated by a disturbance factor and is in a free-running state is driven, counter electromotive voltage 5 occurs, and excessive inrush current may flow through the fan motor.
Further, when permanent magnet synchronous motors (referred to below as PM motors) are used as the fan motors, the excessive inrush current may demagnetize the rotor magnets.
[0006]
One or more aspects of the present invention are
intended to make it possible, in a motor driving device that drives multiple fan motors with a single inverter, when a
fan motor in a free-running state is driven in addition to already driven fan motor(s), to prevent excessive current
from flowing through the fan motor and prevent
demagnetization of a permanent magnet of the PM motor.
Solution to Problem
[0007]
A motor driving device according to an aspect of the present invention is a motor driving device for driving a first permanent magnet synchronous motor and a second permanent magnet synchronous motor, and includes a converter
to generate a direct-current voltage; an inverter to generate a three-phase alternating-current voltage from the
direct-current voltage; three first power lines to supply the three-phase alternating-current voltage to the first
permanent magnet synchronous motor; three second power lines to supply the three-phase alternating-current voltage to the
second permanent magnet synchronous motor; at least two disconnection contactors, each of the disconnection contactors switching between connection and disconnection of
each of at least two of the three second power lines; at least two short-circuit contactors, each of the short4
circuit contactors switching between connection and disconnection between the two second power lines of each of at least two of pairs of the three second power lines; and a
controller to control the at least two disconnection
contactors and the at least two short-5 circuit contactors.
[0008]
An air conditioner according to an aspect of the
present invention is an air conditioner including a first
permanent magnet synchronous motor; a second permanent
10 magnet synchronous motor; and a motor driving device to
drive the first permanent magnet synchronous motor and the
second permanent magnet synchronous motor, wherein the motor
driving device includes: a converter to generate a directcurrent
voltage; an inverter to generate a three-phase
15 alternating-current voltage from the direct-current voltage;
three first power lines to supply the three-phase
alternating-current voltage to the first permanent magnet
synchronous motor; three second power lines to supply the
three-phase alternating-current voltage to the second
permanent magnet synchronous motor; at least two
disconnection contactors, each of the disconnection
contactors switching between connection and disconnection of
each of at least two of the three second power lines; at
least two short-circuit contactors, each of the short25
circuit contactors switching between connection and
disconnection between the two second power lines of each of
at least two of pairs of the three second power lines; and a
controller to control the at least two disconnection
contactors and the at least two short-circuit contactors.
Advantageous Effects of Invention
[0009]
According to an aspect of the present invention, in a
motor driving device that drives a first permanent magnet
synchronous motor and a second permanent magnet synchronous
motor with a single inverter, by providing disconnection
contactors to disconnect between the second permanent magnet
synchronous motor and the inverter and short-circuit
contactors to short-circuit the second permanent magnet
synchronous motor, and connecting the 5 second permanent
magnet synchronous motor to the inverter and driving the
second permanent magnet synchronous motor after shortcircuiting
the second permanent magnet synchronous motor, it
is possible to prevent occurrence of counter electromotive
10 voltage from the second permanent magnet synchronous motor
and demagnetization of a permanent magnet of the second
permanent magnet synchronous motor.
Brief Description of Drawings
[0010]
FIG. 1 is a schematic diagram illustrating a
configuration of a motor driving device according to a first
embodiment and its peripheral circuitry.
FIG. 2 is a table illustrating operational modes in
which disconnection contactors and short-circuit contactors
are controlled.
FIG. 3 is a schematic diagram illustrating a first
example of an operating sequence of a first PM motor, a
second PM motor, an inverter, the disconnection contactors,
and the short-circuit contactors.
FIG. 4 is a schematic diagram illustrating a rotational
frequency command value provided from the inverter to the
first PM motor.
FIG. 5 is a schematic diagram illustrating a second
example of an operating sequence of the first PM motor,
second PM motor, inverter, disconnection contactors, and
short-circuit contactors.
FIG. 6 is a schematic diagram illustrating a third
example of an operating sequence of the first PM motor,
second PM motor, inverter, disconnection contactors, and
short-circuit contactors.
FIG. 7 is a schematic diagram illustrating a fourth
example of an operating sequence of the first PM motor,
second PM motor, inverter, disconnection contactors, and
short-5 circuit contactors.
FIGs. 8A and 8B are schematic diagrams illustrating
hardware configuration examples.
FIG. 9 is a schematic diagram illustrating a
configuration of a motor driving device according to a
second embodiment and its peripheral circuitry.
FIG. 10 is a schematic diagram illustrating a
relationship between a brake current and an overcurrent
detection signal.
FIG. 11 is a block diagram schematically illustrating a
configuration of an air conditioner according to a third
embodiment.
Description of Embodiments
[0011]
First Embodiment
FIG. 1 is a schematic diagram illustrating a
configuration of a motor driving device 100 according to a
first embodiment and its peripheral circuitry.
The motor driving device 100 is connected to an
alternating-current (AC) power supply 121, a first PM motor
120A, and a second PM motor 120B, and includes at least a
converter 101, an inverter 105, disconnection contactors
108A and 108B, short-circuit contactors 109A and 109B, and a
calculator 110.
The motor driving device 100 also includes a bus
voltage sensor 104, first current sensors 106A and 106B, and
second current sensors 107A and 107B.
With the above configuration, the motor driving device
100 drives the first PM motor 120A and second PM motor 120B.
[0012]
The converter 101 generates a direct-current (DC)
voltage. For example, the converter 101 converts an AC
voltage from the AC power supply 121 to a DC voltage by
rectifying the AC voltage with a rectifier 102 and then
smoothing it with a smoothing unit 103, such 5 as a capacitor.
The DC voltage resulting from the conversion by the
converter 101 is output to the inverter 105.
[0013]
The bus voltage sensor 104 detects a DC bus voltage
applied to the inverter 105. A bus voltage value that is a
voltage value of the detected DC bus voltage is supplied to
the calculator 110.
[0014]
The inverter 105 generates a three-phase AC voltage
from the DC voltage supplied from the converter 101, and
outputs the three-phase AC voltage to the first PM motor
120A and second PM motor 120B. The first PM motor 120A and
second PM motor 120B are connected in parallel to the output
of the inverter 105. For example, the first PM motor 120A is
connected to the inverter 105 through a first U-phase power
line 111u, a first V-phase power line 111v, and a first Wphase
power line 111w, and the second PM motor 120B is
connected to the inverter 105 through a second U-phase power
line 112u branched from the first U-phase power line 111u, a
second V-phase power line 112v branched from the first Vphase
power line 111v, and a second W-phase power line 112w
branched from the first W-phase power line 111w.
[0015]
Here, each of the first U-phase power line 111u, first
30 V-phase power line 111v, and first W-phase power line 111w
is a first power line for supplying the three-phase AC
voltage to the first PM motor 120A.
Also, each of the second U-phase power line 112u,
second V-phase power line 112v, and second W-phase power
line 112w is a second power line for supplying the threephase
AC voltage to the second PM motor 120B.
[0016]
The first current sensors 106A and 106B detect currents
flowing through the first PM motor 120A. 5 First current
values that are the detected current values are supplied to
the calculator 110. For example, the first current sensors
106A and 106B are each a sensor that detects a current using
a Hall element.
Here, the first current sensor 106A detects the current
flowing through the first U-phase power line 111u, and the
first current sensor 106B detects the current flowing
through the first W-phase power line 111w. However, the
first embodiment is not limited to such an example. In the
15 first embodiment, it is sufficient that the currents flowing
through at least two first power lines of the first U-phase
power line 111u, first V-phase power line 111v, and first Wphase
power line 111w be detected, and all the currents
flowing through the first power lines may be detected.
When the first current sensors 106A and 106B need not
be particularly distinguished from each other, they will be
referred to as first current sensors 106.
[0017]
The second current sensors 107A and 107B detect
currents flowing through the second PM motor 120B. Second
current values that are the detected current values are
supplied to the calculator 110. For example, the second
current sensors 107A and 107B are each a sensor that detects
a current using a Hall element.
Here, the second current sensor 107A detects the
current flowing through the second U-phase power line 112u,
and the second current sensor 107B detects the current
flowing through the second W-phase power line 112w. However,
the first embodiment is not limited to such an example. In
the first embodiment, it is sufficient that the currents
flowing through at least two second power lines of the
second U-phase power line 112u, second V-phase power line
112v, and second W-phase power line 112w be detected, and
all the currents flowing through the second 5 power lines may
be detected.
When the second current sensors 107A and 107B need not
be particularly distinguished from each other, they are
referred to as second current sensors 107.
[0018]
The disconnection contactors 108A and 108B and the
short-circuit contactors 109A and 109B are inserted between
the inverter 105 and the second PM motor 120B.
[0019]
The disconnection contactors 108A and 108B are inserted
in series in at least two of the second power lines between
the inverter 105 and the second PM motor 120B. Each of the
disconnection contactors 108A and 108B switches between
connection and disconnection of the second power line.
Energization of the second PM motor 120B is controlled by
operation of the disconnection contactors 108A and 108B.
[0020]
For example, when the disconnection contactors 108A and
108B are turned on, the inverter 105 is connected to the
second PM motor 120B, and power from the inverter 105 is
supplied to the second PM motor 120B. On the other hand,
when the disconnection contactors 108A and 108B are turned
off, the inverter 105 is disconnected from the second PM
motor 120B, and no power is supplied from the inverter 105
to the second PM motor 120B.
The disconnection contactors 108A and 108B operate in
the same manner in accordance with commands from the
calculator 110. Thus, when the disconnection contactors 108A
and 108B need not be particularly distinguished from each
other, they will be referred to below as disconnection
contactors 108.
[0021]
Here, the disconnection contactor 108A is inserted in
the second U-phase power line 112u, and 5 the disconnection
contactor 108B is inserted in the second W-phase power line
112w. However, the first embodiment is not limited to such
an example. It is sufficient that disconnection contactors
108 be inserted in at least two second power lines of the
second U-phase power line 112u, second V-phase power line
112v, and second W-phase power line 112w, and it is possible
that disconnection contactors 108 are inserted in all the
power lines 112u, 112v, and 112w.
[0022]
The short-circuit contactors 109A and 109B are inserted
between the disconnection contactors 108 and the second PM
motor 120B. Each of the short-circuit contactors 190A and
190B is inserted between the two second power lines included
in one of the pairs of the second U-phase power line 112u,
second V-phase power line 112v, and second W-phase power
line 112w. Each of the short-circuit contactors 109A and
109B switches between connection and disconnection between
the two second power lines. The presence or absence of short
circuit of the second power lines connected to the second PM
motor 120B can be controlled by operation of the shortcircuit
contactors 109A and 109B.
[0023]
For example, when the short-circuit contactors 109A and
109B are turned on, the second U-phase power line 112u and
second V-phase power line 112v are connected to each other,
and the second V-phase power line 112v and second W-phase
power line 112w are connected to each other, so that the
paths of the currents flowing through the second PM motor
120B are closed in the second PM motor 120B. Thereby, no
power is supplied from the inverter 105 to the second PM
motor 120B, power supplied to the second PM motor 120B is
consumed by the second PM motor 120B itself, and the second
PM motor 120B can be braked. Thus, even when the second PM
motor 120B is in a free-running state, the 5 second PM motor
120B is braked and stops rotating, so that the counter
electromotive voltage can be reduced.
[0024]
On the other hand, when the short-circuit contactors
109A and 109B are turned off, the second U-phase power line
112u and second V-phase power line 112v are disconnected
from each other, the second V-phase power line 112v and
second W-phase power line 112w are disconnected from each
other, the current paths are formed between the inverter 105
and the second PM motor 120B, and power is supplied from the
inverter 105 to the second PM motor 120B.
The short-circuit contactors 109A and 109B operate in
the same manner in accordance with commands from the
calculator 110. Thus, when the short-circuit contactors 109A
and 109B need not be particularly distinguished from each
other, they will be referred to below as short-circuit
contactors 109.
[0025]
Here, the short-circuit contactor 109A is inserted
between the second U-phase power line 112u and the second Vphase
power line 112v, and the short-circuit contactor 109B
is inserted between the second V-phase power line 112v and
the second W-phase power line 112w. However, the first
embodiment is not limited to such an example. It is
sufficient that a short-circuit contactor 109 be inserted
between each of at least two of the pair of the second Uphase
power line 112u and second V-phase power line 112v,
the pair of the second V-phase power line 112v and second Wphase
power line 112w, and the pair of the second U-phase
power line 112u and second W-phase power line 112w, and it
is possible that a short-circuit contactor 109 is inserted
between each of all the pairs.
[0026]
The calculator 110 is a controller 5 that controls
processes in the motor driving device 100.
For example, the calculator 110 performs motor control
calculation and generates driving signals for respective
switching elements of the inverter 105, on the basis of the
detection results of the first current sensors 106, second
current sensors 107, and bus voltage sensor 104. Here, the
calculator 110 performs vector control. Specifically, the
calculator 110 determines, from the detection results of the
first current sensors 106, a current value flowing through
each phase of the first PM motor 120A, and performs
coordinate conversion from stationary three-phase
coordinates to rotational two-phase coordinates, on the
determined current values, thereby calculating first current
values in dq-axes. Similarly, the calculator 110 determines,
from the detection results of the second current sensors 107,
a current value flowing through each phase of the second PM
motor 120B, and performs coordinate conversion from
stationary three-phase coordinates to rotational two-phase
coordinates, on the determined current values, thereby
calculating second current values in dq-axes. The calculator
110 generates the driving signals for the inverter 105 so
that the first current values calculated as above are equal
to ideal values, in consideration of the difference between
the first current values and the second current values.
The above-described vector control is merely an example,
and the calculator 110 may use any control method.
[0027]
Also, the calculator 110 controls the disconnection
contactors 108 and short-circuit contactors 109 in
accordance with commands from a host controller 122.
For example, when stopping the second PM motor 120B,
the calculator 110 switches the disconnection contactors 108
from connection to disconnection and switches the shortcircuit
contactors 109 from disconnection 5 to connection.
[0028]
FIG. 2 is a table illustrating operation modes in which
the disconnection contactors 108 and short-circuit
contactors 109 are controlled in accordance with commands
from the host controller 122.
As illustrated in FIG. 2, upon receiving a command to
cause the second PM motor 120B to operate, i.e., a command
to energize the second PM motor 120B, from the host
controller 122, the calculator 110 turns the disconnection
contactors 108 on, and turns the short-circuit contactors
109 off. On the other hand, upon receiving a command to stop
the second PM motor 120B, i.e., a command to supply no
current to the second PM motor 120B, from the host
controller 122, the calculator 110 turns the disconnection
contactors 108 off, and turns the short-circuit contactors
109 on. Here, “on” indicates that they are in conduction
states, and “off” indicates that they are in open states.
[0029]
The operation will now be described. FIG. 3 is a
schematic diagram illustrating a first example of an
operating sequence of the first PM motor 120A, second PM
motor 120B, inverter 105, disconnection contactors 108, and
short-circuit contactors 109. FIG. 3 illustrates a sequence
in the case of driving the second PM motor 120B that has
been stopped, in addition to the first PM motor 120A that is
being driven.
[0030]
As illustrated in FIG. 3, when the first PM motor 120A
is being driven and the second PM motor 120B is stopped, the
disconnection contactors 108 are turned off, and the power
supply from the inverter 105 to the second PM motor 120B is
disconnected. Meanwhile, the short-circuit contactors 109
are turned on, and the second PM motor 120B is in a shortcircuit
state.
[0031]
Then, the short-circuit contactors 109 are turned off
and the second PM motor 120B is switched from the shortcircuit
state to an open state, and then the disconnection
10 contactors 108 are turned on, resulting in a state where
power is supplied from the inverter 105 to the second PM
motor 120B, and the current paths between the inverter 105
and the second PM motor 120B are connected. Thereby, power
is supplied from the inverter 105 to the second PM motor
120B, and the second PM motor 120B is also driven.
[0032]
Here, it is assumed that the disconnection contactors
108 and short-circuit contactors 109 are, for example,
relays or semiconductor switching elements. Whichever is
used, it takes time to turn on or off. A preparatory period
is provided after the short-circuit contactors 109 are
turned off and before the disconnection contactors 108 are
turned on. This is because it takes time for the
disconnection contactors 108 to switch between the on and
off states, and is to prevent a situation in which the
short-circuit contactors 109 turn off simultaneously with
the disconnection contactors 108 turning on, or a situation
in which the short-circuit contactors 109 are turned off
after the disconnection contactors 108 are turned on.
[0033]
If the short-circuit contactors 109 were turned off
after turning on of the disconnection contactors 108, a
state in which the disconnection contactors 108 and shortcircuit
contactors 109 are both turned on would occur, the
outputs of the inverter 105 would be short-circuited, and
upon operation of the inverter 105, the inverter 105 would
be stopped or damaged due to overcurrent.
[0034]
However, in the case of the switching 5 sequence of FIG.
3, since the AC voltage is suddenly applied to the second PM
motor 120B in a stopped state, inrush current flows at the
time of the switching, which may demagnetize a magnet of a
rotor of the second PM motor 120B. Due to the nature of the
PM motor, when the rotational frequency of the rotor of the
second PM motor 120B is greatly different from the frequency
of the AC voltage output by the inverter 105, the output
voltage of the inverter 105 fails to be synchronized with
the rotor of the second PM motor 120B, which may lead to
step-out.
[0035]
Thus, as illustrated in FIG. 4, before the shortcircuit
contactors 109 are turned off and the disconnection
contactors 108 are turned on, a rotational frequency command
value provided from the inverter 105 to the first PM motor
120A is decreased. While the amount of current flowing
through the first PM motor 120A is small, the short-circuit
contactors 109 are turned off and the disconnection
contactors 108 are turned on, so that the current paths
between the inverter 105 and the second PM motor 120B are
connected. Then, the rotational frequency command value
provided from the inverter 105 to the first PM motor 120A
and second PM motor 120B is increased again.
[0036]
Since the disconnection contactors 108 are turned on
while the amount of current flowing through the first PM
motor 120A is small, the second PM motor 120B easily follows
the first PM motor 120A, and the step-out can be prevented.
[0037]
In the operating sequence illustrated in FIG. 3, while
the first PM motor 120A is being driven and the second PM
motor 120B is stopped, the short-circuit contactors 109 are
turned on. However, since the disconnection contactors 108
are turned off and the power supply from the 5 inverter 105 to
the second PM motor 120B is disconnected, the short-circuit
contactors 109 may be turned off.
[0038]
Also, the rotational frequency of the first PM motor
120A is decreased, the frequency of the AC voltage output by
the inverter 105 is also decreased, and the difference
between the rotational frequency of the second PM motor 120B
in the stopped state and the frequency of the AC voltage
output by the inverter 105 is decreased. This facilitates
synchronous pull-in of the rotor of the second PM motor 120B,
and can prevent step-out of the second PM motor 120B.
[0039]
The following describes, with reference to FIG. 5, an
operation of preventing step-out of the second PM motor 120B
in a simpler way without performing control of the
rotational frequency command value. In FIG. 5, the operation
when only the first PM motor 120A is being driven and the
second PM motor 120B is stopped is the same as that in FIG.
3, and the subsequent operation differs from the operating
sequence illustrated in FIG. 3.
[0040]
As illustrated in FIG. 5, when the first PM motor 120A
is being driven and the second PM motor 120B is stopped, a
voltage is output from the inverter 105, the disconnection
contactors 108 are turned off, and the short-circuit
contactors 109 are turned on.
[0041]
Then, the output of voltage from the inverter 105 is
stopped, and the driving of the first PM motor 120A is
stopped. In a switching period during which the first PM
motor 120A and second PM motor 120B are stopped, the shortcircuit
contactors 109 are turned off and the second PM
motor 120B is switched from the short-circuit state to the
open state, and then the disconnection 5 contactors 108 are
turned on and the current paths between the inverter 105 and
the second PM motor 120B are connected. Then, the voltage
from the inverter 105 is output, and the first PM motor 120A
and second PM motor 120 connected to the inverter 105 are
driven.
[0042]
As described above, the current paths between the
inverter 105 and the second PM motor 120B are connected
while the first PM motor 120A and second PM motor 120B are
stopped. This prevents a large voltage from being suddenly
applied to the second PM motor 120B after the second PM
motor 120B is driven, and can prevent step-out of the second
PM motor 120B.
[0043]
The following describes an operation of stopping the
second PM motor 120B that is being driven.
FIG. 6 is a schematic diagram illustrating a third
example of an operating sequence of the first PM motor 120A,
second PM motor 120B, inverter 105, disconnection contactors
108, and short-circuit contactors 109.
FIG. 6 illustrates a sequence in the case of stopping
the second PM motor 120B that is being driven.
As illustrated in FIG. 2, when the second PM motor 120B
is driven, the disconnection contactors 108 are turned on,
and when it is stopped, the short-circuit contactors 109 are
turned on to prevent free running.
[0044]
Here, it is assumed that the disconnection contactors
108 and short-circuit contactors 109 are, for example,
relays or semiconductor switching elements. Whichever
contactor is used, it takes time to turn on or off. The
short-circuit contactors 109 are inserted to short-circuit
the phases. Thus, as illustrated in FIG. 6, the voltage
output of the inverter 105 is stopped 5 once, and then the
state of the short-circuit contactors 109 is switched. Thus,
as illustrated in FIG. 6, a switching period during which
the inverter 105 is stopped is provided.
[0045]
Since it also takes time for the state of the
disconnection contactors 108 to switch, a preparatory period
is provided after the disconnection contactors 108 are
turned off and before the short-circuit contactors 109 are
turned on.
[0046]
FIG. 7 is a schematic diagram illustrating a fourth
example of an operating sequence of the first PM motor 120A,
second PM motor 120B, inverter 105, disconnection contactors
108, and short-circuit contactors 109.
As described above, the disconnection contactors 108
are inserted in series with respect to the inverter 105 and
second PM motor 120B. Thus, when the disconnection
contactors 108 are turned off, no voltage is applied from
the inverter 105 to the second PM motor 120B. Thus, by
turning the disconnection contactors 108 off while the
voltage is being output by the inverter 105, and turning the
short-circuit contactors 109 on after the disconnection
contactors 108 are turned off, it is possible to stop the
second PM motor 120B without stopping the inverter 105 and
first PM motor 120A.
[0047]
In this case, it is not necessary to provide the
switching period as illustrated in FIG. 6. However, since it
takes time for the state of the disconnection contactors 108
to switch, a preparatory period is provided after the
disconnection contactors 108 are turned off and before the
short-circuit contactors 109 are turned on.
[0048]
Part or the whole of the calculator 5 110 and host
controller 122 described above can be formed by, for example,
a memory 10 and a processor 11, such as a central processing
unit (CPU), that executes a program stored in the memory 10,
as illustrated in FIG. 8A. Such a program may be provided
via a network, or may be recorded and provided in a
recording medium. Such a program may be provided as a
program product, for example.
In this case, part or the whole of the calculator 110
and host controller 122 may be implemented by a single
processor 11, or may be implemented by different processors
11.
[0049]
Also, part of the calculator 110 and host controller
122 may be formed by processing circuitry 12, such as a
single circuit, a composite circuit, a programmed processor,
a parallel-programmed processor, application specific
integrated circuits (ASICs), or a field programmable gate
array (FPGA), as illustrated in FIG. 8B, for example.
[0050]
Second Embodiment
In the case of the motor driving device 100 according
to the first embodiment, it is conceivable that when the
disconnection contactors 108 are turned off and the shortcircuit
contactors 109 are turned on, an increase in the
rotational frequency of the second PM motor 120B due to free
running increases the motor current, thereby causing
problems, such as demagnetization. Thus, the second
embodiment addresses such problems.
[0051]
FIG. 9 is a schematic diagram illustrating a
configuration of a motor driving device 200 according to a
second embodiment and its peripheral circuitry.
The motor driving device 200 includes at least a
converter 101, an inverter 105, disconnection 5 contactors 108,
short-circuit contactors 109, and a calculator 210.
The motor driving device 100 also includes a bus
voltage sensor 104, first current sensors 106, second
current sensors 107, and an overcurrent detector 213.
With the above configuration, the motor driving device
200 drives a first PM motor 120A and a second PM motor 120B.
[0052]
The converter 101, inverter 105, disconnection
contactors 108, short-circuit contactors 109, bus voltage
sensor 104, first current sensors 106, and second current
sensors 107 of the second embodiment are the same as those
of the first embodiment.
However, at least one of the second current sensors
107A and 107B is used as a brake current sensor that detects
a current flowing through the second PM motor 120B when the
short-circuit contactors 109 are turned on. Here, it is
assumed that the second current sensor 107A is used as the
brake current sensor, and the second current sensor 107A
will also be referred to as the brake current sensor 214.
Also, the current value detected by the brake current sensor
214 when the short-circuit contactors 109 are turned on will
be referred to as the brake current value.
The brake current value detected by the brake current
sensor 214 is provided to the overcurrent detector 213.
[0053]
When the short-circuit contactors 109 are turned on,
the overcurrent detector 213 determines, on the basis of the
brake current value, whether a brake current that is the
current flowing through the second PM motor 120B is an
overcurrent. For example, when the brake current value is
greater than an overcurrent determination value that is a
predetermined threshold, the overcurrent detector 213
detects that the brake current is an overcurrent. On the
other hand, when the brake current value is 5 not greater than
the overcurrent determination value, the overcurrent
detector 213 detects that the brake current is not an
overcurrent.
Then, according to the result of the above detection,
the overcurrent detector 213 provides the calculator 210
with an overcurrent detection signal indicating whether the
brake current is an overcurrent, thereby informing the
calculator 210 of whether the brake current is an
overcurrent.
[0054]
The calculator 210 is a controller that controls
processes in the motor driving device 200.
The calculator 210 performs the same processing as the
calculator 110 of the first embodiment. In addition, after
the short-circuit contactors 109 are turned on, when the
calculator 210 receives, from the overcurrent detector 213,
an overcurrent detection signal indicating that the brake
current is an overcurrent, the calculator 210 switches the
short-circuit contactors 109 from connection to
disconnection.
[0055]
FIG. 10 is a schematic diagram illustrating a
relationship between the brake current and the overcurrent
detection signal.
FIG. 10 is merely a schematic diagram illustrating an
operation example, and illustrates waveforms and the like in
a simple manner.
[0056]
FIG. 10 illustrates an operation in a case where, when
the disconnection contactors 108 are turned off and the
short-circuit contactors 109 are turned on, the brake
current value, which is the current value of the current
flowing through the second PM motor 120B, gradually
increases. As described in the first embodiment, 5 the state
where the disconnection contactors 108 are turned off and
the short-circuit contactors 109 are turned on is a state
where no power is supplied from the inverter 105 to the
second PM motor 120B and brake current is allowed to flow to
prevent free-running rotation of the second PM motor 120B.
Thus, as illustrated in FIG. 10, it is a state where the
rotational frequency R of the second PM motor 120B is not
zero and thus brake current is flowing through the second PM
motor 120B.
[0057]
When the rotational frequency R of free running of the
second PM motor 120B gradually increases due to increase of
outside wind or other reasons, the counter electromotive
voltage of the second PM motor 120B increases, and thus the
brake current value Bi also increases.
[0058]
When the brake current value Bi exceeds the overcurrent
determination value Th, an overcurrent determination signal
S changes from a state where it indicates No to a state
where it indicates Yes. Here, when the overcurrent
determination signal S is in the state where it indicates No,
it indicates that the brake current is not an overcurrent,
and when the overcurrent determination signal S is in the
state where it indicates Yes, it indicates that the brake
30 current is an overcurrent.
[0059]
When the overcurrent determination signal S enters the
state where it indicates Yes, the short-circuit contactors
109 are turned off. This brings the second PM motor 120B out
of the short-circuit state, and places the terminals of the
second PM motor 120B in open states, so that the brake
current value Bi becomes zero.
As described above, the disconnection contactors 108
are 5 left turned off.
[0060]
Thus, in the braking state for reducing free-running
rotation of the second PM motor 120B, when the brake current
is increased, it is possible to prevent demagnetization of
the second PM motor 120B and improve the reliability of the
device.
[0061]
An arrangement relationship of the short-circuit
contactors 109, brake current sensor 214, and second PM
motor 120B will now be described.
As described above, the overcurrent detector 213
performs the overcurrent determination on the basis of the
value detected by the brake current sensor 214. Thus, the
brake current sensor 214 is disposed between the short20
circuit contactors 109 and the second PM motor 120B.
[0062]
Part or the whole of the overcurrent detector 213 can
be formed by the memory 10 and processor 11 as illustrated
in FIG. 8A, for example. In this case, the overcurrent
detector 213 may be implemented by a processor 11 that
implements the calculator 210, or may be implemented by
another processor 11.
[0063]
Also, part of the overcurrent detector 213 can be
formed by a processing circuitry 12 as illustrated in FIG.
8B, for example.
[0064]
In FIG. 9, the overcurrent detector 213 is provided.
However, instead of providing the overcurrent detector 213,
the calculator 210 may perform the overcurrent determination
performed by the overcurrent detector 213.
[0065]
Third Embodiment
Here, an air conditioner in which 5 the motor driving
device 100 or 200 according to the first or second
embodiment is installed will be described.
[0066]
FIG. 11 is a block diagram schematically illustrating a
configuration of an air conditioner 300 according to a third
embodiment.
The air conditioner 300 includes an outdoor unit 330
and an indoor unit 340.
The outdoor unit 330 is installed outdoors, the indoor
15 unit 340 is installed indoors, and they condition indoor air.
Here, the description of the detailed configuration and
operation principle of the air conditioner 300 will be
omitted.
[0067]
The outdoor unit 330 includes a motor driving device
100 or 200, a first PM motor 120A, a second PM motor 120B,
an AC power supply 121, a host controller 122, a first fan
331A, a second fan 331B, a first heat exchanger 332A, and a
second heat exchanger 332B.
[0068]
The motor driving device 100 or 200 of the third
embodiment is the same as that of the first or second
embodiment.
The first PM motor 120A and second PM motor 120B of the
30 third embodiment are the same as those of the first
embodiment. The first PM motor 120A is connected to the
first fan 331A and used to rotate the first fan 331A. The
second PM motor 120B is connected to the second fan 331B and
used to rotate the second fan 331B.
The AC power supply 121 and host controller 122 of the
third embodiment are the same as those of the first
embodiment.
[0069]
The first fan 331A is used to vent air 5 heated or cooled
by the first heat exchanger 332A.
The second fan 331B is used to vent air heated or
cooled by the second heat exchanger 332B.
The first heat exchanger 332A exchanges heat of
refrigerant.
The second heat exchanger 332B exchanges heat of
refrigerant.
[0070]
In the case of a large air conditioner, the path
through which refrigerant flows in a refrigeration cycle may
be switched depending on the required air conditioning
capacity. For example, in the air conditioner 300, when the
required air conditioning capacity is low, heat exchange is
performed while refrigerant is flowed through only the first
heat exchanger 332A. In this case, since heat exchange is
not performed by the second heat exchanger 332B, the second
PM motor 120B need not be driven. In this case, the
disconnection contactors 108 are turned off, and power is
supplied from the inverter 105 to only the first PM motor
120A.
[0071]
In this case, since the terminals of the second PM
motor 120B are in open states, when outside wind blows, the
second PM motor 120B enters a free-running state. The free30
running rotation is reduced by turning the short-circuit
contactors 109 on, as described in the first or second
embodiment.
[0072]
On the other hand, when the required air conditioning
capacity is high, refrigerant is flowed through both the
first heat exchanger 332A and second heat exchanger 332B. In
this case, both the first PM motor 120A and second PM motor
120B need to be driven. At this time, the disconnection
contactors 108 are turned on, and 5 the short-circuit
contactors 109 are turned off, thereby allowing the two fans
331A and 331B to be rotated.
[0073]
As described above, the driving of the multiple PM
motors 120A and 120B can be switched depending on the
operating condition of the air conditioner 300, by the motor
driving device 100 or 200 described in the first or second
embodiment.
[0074]
Although the outdoor unit 330 illustrated in FIG. 11 is
of a top-flow type, the outdoor unit 330 may be of a sideflow
type.
[0075]
In the above-described first to third embodiments, at
least two disconnection contactors may be inserted in series
in at least two power lines of the first U-phase power line
111u, first V-phase power line 111v, and first W-phase power
line 111w between the first PM motor 120A and the positions
where the second U-phase power line 112u, second V-phase
power line 112v, and second W-phase power line 112w are
branched. Also, at least two short-circuit contactors may be
inserted between the first PM motor 120A and the
disconnection contactors inserted in the at least two power
lines of the first U-phase power line 111u, first V-phase
power line 111v, and first W-phase power line 111w so that
they connect or disconnect between the second U-phase power
line 112u, second V-phase power line 112v, and second Wphase
power line 112w.
In such a case, in the second embodiment, a brake
current sensor is provided also in the first U-phase power
line 111u, first V-phase power line 111v, or first W-phase
power line 111w.
[0076]
In the above-described first to third 5 embodiments, the
current values of the respective phases of the first PM
motor 120A and second PM motor 120B are detected by the
first current sensors 106 and second current sensors 107.
However, the first to third embodiments are not limited to
such an example. For example, it is also possible that shunt
resistor(s) (not illustrated) are disposed at position(s),
such as point P1 or points P2-P4 in FIG. 1, and the
calculator 110 or 210 calculates the current values from the
terminal voltage(s). In such a case, one of the set of the
first current sensors 106 and the set of the second current
sensors 107 may be removed. However, in the second
embodiment, at least one brake current sensor 214 is
required.
[0077]
As described above, in the first to third embodiments,
the disconnection contactors 108 and short-circuit
contactors 109 are provided. Thereby, it is possible to
prevent free running of the second PM motor 120B.
[0078]
The short-circuit contactors 109 are provided between
the disconnection contactors 108 and the second PM motor
120B. Thereby, it is possible to prevent overcurrent from
flowing through the inverter 105 when the short-circuit
contactors 109 are turned on.
[0079]
When the driving of the second PM motor 120B is stopped,
the disconnection contactors 108 are switched from
connection to disconnection, and the short-circuit
contactors 109 are switched from disconnection to connection.
Thereby, even when the inverter 105 is operating, it is
possible to stop the second PM motor 120B and prevent free
running of the second PM motor 120B that is stopped.
[0080]
When the driving of the second PM motor 5 120B is stopped,
the disconnection contactors 108 are switched from
connection to disconnection, and then the short-circuit
contactors 109 are switched from disconnection to connection.
Thereby, it is possible to prevent overcurrent in the
inverter.
[0081]
In the second embodiment, when the brake current value
detected by the brake current sensor 214 is greater than the
predetermined threshold, the calculator 210 switches the
15 short-circuit contactors 109 from connection to
disconnection. Thereby, it is possible to prevent problems,
such as demagnetization in the second PM motor 120B.
[0082]
The brake current sensor 214 is provided between the
short-circuit contactors 109 and the second PM motor 120B,
and thus can accurately detect a current flowing through the
second PM motor 120B.
[0083]
In the third embodiment, the first PM motor 120A is
used to rotate the first fan 331A, and the second PM motor
120B is used to rotate the second fan 331B. Thus, it is
possible to prevent the second PM motor 120B from free
running due to outside wind or the like.
Reference Signs List
[0084]
100, 200 motor driving device, 101 converter, 105
inverter, 106 first current sensor, 107 second current
sensor, 108 disconnection contactor, 109 short-circuit
contactor, 110, 210 calculator, 120A first PM motor, 120B
second PM motor, 121 AC power supply, 122 host controller,
300 air conditioner, 330 outdoor unit, 340 indoor unit.

We Claim :
1. A motor driving device for driving a first permanent
magnet synchronous motor and a second permanent magnet
synchronous motor, the motor driving 5 device comprising:
a converter to generate a direct-current voltage;
an inverter to generate a three-phase alternatingcurrent
voltage from the direct-current voltage;
three first power lines to supply the three-phase
alternating-current voltage to the first permanent magnet
synchronous motor;
three second power lines to supply the three-phase
alternating-current voltage to the second permanent magnet
synchronous motor;
at least two disconnection contactors, each of the
disconnection contactors switching between connection and
disconnection of each of at least two of the three second
power lines;
at least two short-circuit contactors, each of the
20 short-circuit contactors switching between connection and
disconnection between the two second power lines of each of
at least two of pairs of the three second power lines; and
a controller to control the at least two disconnection
contactors and the at least two short-circuit contactors.
2. The motor driving device of claim 1, wherein the at
least two short-circuit contactors are provided between the
at least two disconnection contactors and the second
permanent magnet synchronous motor.
3. The motor driving device of claim 1 or 2, wherein when
stopping driving of the second permanent magnet synchronous
motor, the controller switches the at least two
disconnection contactors from the connection to the
disconnection and switches the at least two short-circuit
contactors from the disconnection to the connection.
4. The motor driving device of claim 3, wherein when
stopping driving of the second permanent 5 magnet synchronous
motor, the controller switches the at least two
disconnection contactors from the connection to the
disconnection, and then switches the at least two shortcircuit
contactors from the disconnection to the connection.
5. The motor driving device of claim 3 or 4, further
comprising:
a current sensor to detect a current value of a current
flowing through the second permanent magnet synchronous
motor; and an overcurrent detector to determine whether the
current value is greater than a predetermined threshold,
wherein after the controller switches the at least two
short-circuit contactors from the disconnection to the
connection, when the overcurrent detector determines that
the current value is greater than the predetermined
threshold, the controller switches the at least two shortcircuit
contactors from the connection to the disconnection.
6. The motor driving device of claim 3 or 4, further
comprising a current sensor to detect a current value of a
current flowing through the second permanent magnet
synchronous motor,
wherein after switching the at least two short-circuit
30 contactors from the disconnection to the connection, the
controller determines whether the current value is greater
than a predetermined threshold, and when the current value
is greater than the predetermined threshold, switches the at
least two short-circuit contactors from the connection to
the disconnection.
7. The motor driving device of claim 6, wherein the
current sensor is provided between the at least two shortcircuit
contactors and the second 5 permanent magnet
synchronous motor.
8. The motor driving device of any one of claims 1 to 7,
wherein
10 the first permanent magnet synchronous motor is used to
rotate a first fan, and
the second permanent magnet synchronous motor is used
to rotate a second fan.
9. An air conditioner comprising:
a first permanent magnet synchronous motor;
a second permanent magnet synchronous motor; and
a motor driving device to drive the first permanent
magnet synchronous motor and the second permanent magnet
20 synchronous motor,
wherein the motor driving device includes:
a converter to generate a direct-current voltage;
an inverter to generate a three-phase alternatingcurrent
voltage from the direct-current voltage;
three first power lines to supply the three-phase
alternating-current voltage to the first permanent magnet synchronous motor;
three second power lines to supply the three-phase alternating-current voltage to the second permanent magnet
synchronous motor;
at least two disconnection contactors, each of the disconnection contactors switching between connection and disconnection of each of at least two of the three second power lines;
at least two short-circuit contactor disconnection between the two at least two of pairs of the three a controller disconnection contactor
contactors.