1
FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
ELECTRIC MOTOR DRIVE 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 1008310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
2
DESCRIPTION
Field
[0001] The present disclosure relates to an electric
motor drive device and an air conditioner.5
Background
[0002] There is an electric motor drive device that
includes a three-phase AC diode bridge and an inverter,
converts power supplied from a three-phase AC power supply10
into three-phase AC power having a desired voltage and
frequency, and supplies the three-phase AC power to a motor
(for example, Patent Literature 1).
[0003] In the electric motor drive device having a
configuration including the three-phase diode bridge, when15
an input three-phase AC voltage is imbalanced, an imbalance
occurs in an input current, and pulsation also occurs in a
DC voltage after rectification in the three-phase diode
bridge. When pulsation occurs in the DC voltage after
rectification, there is a possibility that a defect occurs20
such as breaker trip or a failure of a component mounted on
a substrate. In response to such a problem, an electric
motor drive device described in Patent Literature 1
determines whether or not the three-phase AC is in an
imbalanced state on the basis of a line voltage of a three-25
phase AC power supply. When the three-phase AC is in an
imbalanced state, the electric motor drive device protects
circuit components by reducing an output of an inverter.
Citation List30
Patent Literature
[0004] Patent Literature 1: Japanese Patent Application
Laid-open No. 2017-22920
3
Summary of Invention
Problem to be solved by the Invention
[0005] In the conventional electric motor drive device
described above, in the processing of determining whether or5
not a three-phase AC is in an imbalanced state, the line
voltage is estimated, and an imbalance rate calculated on
the basis of an estimation result of the line voltage is
compared with a predetermined threshold to detect the
imbalanced state. For this reason, in the conventional10
electric motor drive device, it is necessary to provide a
voltage detection circuit for at least two phases of three-
phase AC, which leads to an increase in size of the device,
and further, processing becomes complicated and a processing
load increases. For this reason, it is desired to achieve15
an electric motor drive device capable of downsizing the
device and reducing a processing load.
[0006] The present disclosure has been made in view of
the above, and an object of the present disclosure is to
provide an electric motor drive device capable of achieving20
downsizing of the device and reduction of a processing load.
Means to Solve the Problem
[0007] To solve the above problem and achieve an object,
an electric motor drive device according to the present25
disclosure includes: a three-phase diode bridge to rectify
a three-phase alternating-current (AC) voltage, to convert
the AC voltage into a direct-current (DC) voltage; a
smoothing capacitor to smooth the DC voltage; a DC reactor
provided between the three-phase diode bridge and the30
smoothing capacitor; an inverter to convert the DC voltage
smoothed by the smoothing capacitor into an AC voltage, and
output the AC voltage to a motor; a voltage detecting unit
4
to detect a DC voltage output from the three-phase diode
bridge; and an inverter control unit to detect an imbalanced
state of the three-phase AC voltage based on a DC voltage
value, and control the inverter based on a detection result
of the imbalanced state, the DC voltage value being a5
detection value of the DC voltage obtained by the voltage
detecting unit.
Effects of the Invention
[0008] The electric motor drive device according to the10
present disclosure has an effect of being able to achieve
downsizing of the device and reduction of a processing load.
Brief Description of Drawings
[0009] FIG. 1 is a diagram illustrating an exemplary15
configuration of an electric motor drive device according to
a first embodiment.
FIG. 2 is a flowchart illustrating an example of an
operation of the electric motor drive device according to
the first embodiment.20
FIG. 3 is a graph for explaining a ripple voltage
calculated by an inverter control unit according to the first
embodiment.
FIG. 4 is a diagram illustrating an exemplary
configuration of an electric motor drive device according to25
a second embodiment.
FIG. 5 is a graph illustrating an example of a
relationship between each phase voltage of three-phase AC
and a line voltage.
FIG. 6 is a graph illustrating an example of a30
relationship between each phase voltage of three-phase AC
and a DC voltage after rectifying each phase voltage.
FIG. 7 is a graph illustrating a relationship between
5
a DC voltage and a line voltage at a zero-cross point of a
phase voltage.
FIG. 8 is a flowchart illustrating an example of an
operation of the electric motor drive device according to
the second embodiment.5
FIG. 9 is a diagram illustrating an exemplary
configuration of an air conditioner according to a third
embodiment.
Description of Embodiments10
[0010] Hereinafter, an electric motor drive device and an
air conditioner according to embodiments of the present
disclosure will be described in detail with reference to the
drawings.
[0011] First Embodiment.15
FIG. 1 is a diagram illustrating an exemplary
configuration of an electric motor drive device 100 according
to a first embodiment. The electric motor drive device 100
is connected to a power supply 1 via three power supply lines
L1 to L3, and receives supply of three-phase AC power from20
the power supply 1 to drive a motor 2. That is, the electric
motor drive device 100 converts three-phase AC power supplied
from the power supply 1 into three-phase AC power having a
desired voltage and frequency, to generate drive power for
the motor 2. Note that the motor 2 is a three-phase motor.25
[0012] The electric motor drive device 100 includes: a
three-phase diode bridge 10 which rectifies a three-phase AC
voltage supplied from the power supply 1 which is a three-
phase AC power supply, to convert the three-phase AC voltage
into a DC voltage; an electrolytic capacitor 3 which is a30
smoothing capacitor for smoothing the DC voltage output from
the three-phase diode bridge 10; an inverter 20 which
converts the DC voltage smoothed by the electrolytic
6
capacitor 3 into a three-phase AC voltage, and applies the
three-phase AC voltage to the motor 2; and a DC reactor 30
which is provided between the three-phase diode bridge 10
and the electrolytic capacitor 3, and reduces a harmonic
current included in a DC current flowing between the three-5
phase diode bridge 10 and the inverter 20. Further, the
electric motor drive device 100 includes: a voltage detecting
unit 40 which is connected between the three-phase diode
bridge 10 and the DC reactor 30, and detects the DC voltage
output from the three-phase diode bridge 10; and an inverter10
control unit 50 to which a DC voltage value is input, the DC
voltage value being a detection value of the DC voltage
obtained by the voltage detecting unit 40, and gives a
command generated on the basis of the input DC voltage value
to the inverter 20 to generate drive power for the motor 2.15
Note that, although not illustrated in FIG. 1, the detection
value of the voltage output from the inverter 20 and a
voltage command are input to the inverter control unit 50.
The inverter control unit 50 generates a command to the
inverter 20 on the basis of the detection value of the20
voltage output from the inverter 20, the voltage command,
and the above-described DC voltage value. The voltage
detecting unit 40 is implemented by, for example, a voltage
sensor. The inverter control unit 50 is implemented by, for
example, a microcontroller.25
[0013] Although detailed operation will be separately
described, in the electric motor drive device 100, the
inverter control unit 50 determines whether or not the three-
phase AC voltage supplied from the power supply 1 is in an
imbalanced state on the basis of the detection result of the30
DC voltage obtained by the voltage detecting unit 40, and
reduces an output of the inverter 20 when the three-phase AC
voltage is in the imbalanced state.
7
[0014] Here, as described above, when there is an
imbalance in the input three-phase AC voltage, an imbalance
occurs in an input current, and pulsation (hereinafter
referred to as a ripple) also occurs in the DC voltage
rectified by the three-phase diode bridge 10. That is, when5
the three-phase AC voltage is in an imbalanced state, a
ripple component included in the DC voltage increases.
Therefore, it is possible to detect an imbalance of the
three-phase AC voltage by monitoring the DC voltage rectified
by the three-phase diode bridge 10. The inverter control10
unit 50 of the electric motor drive device 100 according to
the present embodiment detects the imbalance of the three-
phase AC voltage by using such characteristics. As a result,
it is not necessary to provide a circuit for detecting a
voltage of each phase of the three-phase AC input from the15
power supply 1, and it is possible to reduce the size and
cost of the device.
[0015] In addition, the ripple of the DC voltage also
occurs when a load of the inverter 20 to which the DC voltage
is applied fluctuates. Therefore, the electric motor drive20
device 100 is configured to detect the DC voltage between
the three-phase diode bridge 10 and the DC reactor 30 where
an influence of the load fluctuation is small. Note that,
a configuration may be adopted in which the DC voltage is
detected at a position (for example, between the electrolytic25
capacitor 3 and the inverter 20) different from the DC
voltage detection location illustrated in FIG. 1, when an
assumed maximum variation amount of the load connected to
the inverter 20 is small, that is, when the ripple generated
with the load variation is negligibly small as compared to30
the ripple generated with the imbalance of the three-phase
AC voltage.
[0016] FIG. 2 is a flowchart illustrating an example of
8
an operation of the electric motor drive device 100 according
to the first embodiment. Specifically, the flowchart of FIG.
2 illustrates an exemplary operation in which the inverter
control unit 50 of the electric motor drive device 100
determines the presence or absence of a power supply voltage5
imbalance, and controls the inverter 20 in accordance with
the determination result.
[0017] When the electric motor drive device 100 is
executing the power conversion operation for generating the
drive power for the motor 2, the inverter control unit 5010
repeats the operation according to the flowchart of FIG. 2.
That is, when the electric motor drive device 100 drives the
motor 2, the inverter control unit 50 repeatedly executes a
series of processing from the start to the end illustrated
in FIG. 2 at a predetermined cycle.15
[0018] Specifically, the inverter control unit 50 first
acquires a DC voltage value (step S1). In particular, the
inverter control unit 50 acquires a detection value of a DC
voltage from the voltage detecting unit 40.
[0019] Next, the inverter control unit 50 calculates a20
ripple voltage on the basis of the DC voltage value acquired
in step S1 (step S2). The ripple voltage calculated by the
inverter control unit 50 in step S2 will be described with
reference to FIG. 3. FIG. 3 is a graph for explaining a
ripple voltage calculated by the inverter control unit 5025
according to the first embodiment. In FIG. 3, reference
character “Vdc” represents a DC voltage detected by the
voltage detecting unit 40, and reference characters “VL1”,
“VL2”, and “VL3” represent voltages of respective phases of
three-phase AC input from the three power supply lines L1 to30
L3 to the electric motor drive device 100. The horizontal
axis represents time, and the vertical axis represents a
voltage. FIG. 3 illustrates an example of a correspondence
9
relationship between the DC voltage Vdc and the voltages VL1,
VL2, and VL3 of the individual phases of the three-phase AC.
As illustrated in FIG. 3, the ripple voltage calculated by
the inverter control unit 50 is a difference between
magnitudes of adjacent ripples included in the DC voltage,5
that is, a voltage difference between adjacent vertexes. In
step S2, the inverter control unit 50 detects a vertex of
the ripple by analyzing the latest DC voltage value acquired
from the voltage detecting unit 40 and a DC voltage value
acquired in the past, and calculates the ripple voltage from10
the detected vertex. For example, when the inverter control
unit 50 detects the vertex of the latest ripple by analyzing
the DC voltage value, the inverter control unit 50 obtains
a difference between the detected vertex and the previously
detected vertex of the ripple, and sets this difference as15
the ripple voltage.
[0020] Next, the inverter control unit 50 compares the
ripple voltage calculated in step S2 with a predetermined
threshold for imbalance detection (hereinafter referred to
as an imbalance detection threshold) (step S3). Note that,20
the imbalance detection threshold is determined in advance,
for example, by performing an operation simulation of the
electric motor drive device 100.
[0021] When the ripple voltage is larger than the
imbalance detection threshold (step S3: Yes), the inverter25
control unit 50 determines that the three-phase AC voltage
is in an imbalanced state, and reduces the output of the
inverter 20 (step S4). For example, the inverter control
unit 50 controls the inverter 20 so that a maximum output of
the inverter 20 does not exceed N% of a maximum output in30
normal state. Note that, N<100 is satisfied. The normal
state is a state in which the three-phase AC voltage is not
imbalanced. N described above may be a variable value. For
10
example, when the ripple voltage and the imbalance detection
threshold are greatly different, N may be changed so as to
be a small value. In addition, a plurality of different
imbalance detection thresholds and a value of N corresponding
to each imbalance detection threshold may be prepared, and5
a value of N to be used may be determined on the basis of a
comparison result between the ripple voltage and each
imbalance detection threshold.
[0022] When the ripple voltage is equal to or lower than
the imbalance detection threshold (step S3: No), the inverter10
control unit 50 determines that the three-phase AC voltage
is not in an imbalanced state, that is, determines that the
three-phase AC voltage is in the normal state, and continues
a normal operation of the inverter 20 (step S5). Note that,
in the normal operation, the inverter control unit 5015
performs control such that a voltage output from the inverter
20 follows the voltage command.
[0023] As described above, the electric motor drive
device 100 according to the present embodiment includes: the
voltage detecting unit 40 which detects a DC voltage between20
the three-phase diode bridge 10 and the DC reactor 30; and
the inverter control unit 50 which detects an imbalanced
state of the three-phase AC voltage on the basis of a ripple
of the DC voltage detected by the voltage detecting unit 40,
and the inverter control unit 50 reduces the output of the25
inverter 20 upon detecting the imbalanced state of the three-
phase AC voltage. According to the present embodiment, it
is possible to achieve the electric motor drive device 100
capable of preventing a defect such as breaker trip and a
failure of a component mounted on the substrate when an30
imbalance of the three-phase AC voltage occurs, and it is
possible to achieve downsizing of the device and reduction
of a processing load.
11
[0024] Second Embodiment.
The electric motor drive device 100 according to the
above first embodiment determines whether or not the three-
phase AC voltage is in an imbalanced state by comparing a
predetermined imbalance detection threshold and a ripple5
voltage calculated on the basis of a DC voltage detected by
the voltage detecting unit 40 provided between the three-
phase diode bridge 10 and the DC reactor 30. On the other
hand, in the present embodiment, a description will be given
of an electric motor drive device 100a capable of accurately10
detecting an imbalance even in a case of a large fluctuation
of a DC voltage due to an influence of a fluctuation of a
load connected to the inverter 20.
[0025] FIG. 4 is a diagram illustrating an exemplary
configuration of the electric motor drive device 100a15
according to a second embodiment. In FIG. 4, components in
common with those of the electric motor drive device 100
according to the first embodiment illustrated in FIG. 1 are
denoted by identical reference numerals. The description of
the components denoted by reference numerals identical to20
those in FIG. 1 will be omitted.
[0026] The electric motor drive device 100a has a
configuration in which the inverter control unit 50 of the
electric motor drive device 100 according to the first
embodiment is replaced with an inverter control unit 50a,25
and a zero-cross point detecting unit 60 is added.
[0027] The zero-cross point detecting unit 60 monitors
any one phase of a three-phase AC voltage input from the
power supply 1 to the electric motor drive device 100a,
detects a zero-cross point of the voltage, and outputs a30
detection result to the inverter control unit 50a. In the
configuration illustrated in FIG. 4, the zero-cross point
detecting unit 60 detects a zero-cross point of the voltage
12
VL1 of the power supply line L1. The zero-cross point
detecting unit 60 is implemented by, for example, a voltage
sensor, a logic circuit that determines a sign of a voltage
detection value obtained by the voltage sensor, and the like.
[0028] The inverter control unit 50a generates a command5
to the inverter 20 on the basis of the DC voltage value
detected by the voltage detecting unit 40 and the zero-cross
point detected by the zero-cross point detecting unit 60.
Specifically, the inverter control unit 50a calculates a
voltage (hereinafter, a voltage of one phase is referred to10
as a phase voltage) of each phase of the three-phase AC
voltage input to the electric motor drive device 100a, on
the basis of the DC voltage value and the zero-cross point.
Then, the inverter control unit 50a determines whether or
not the three-phase AC voltage is in an imbalanced state on15
the basis of the calculated effective value of each phase
voltage, and controls the output of the inverter 20 in
accordance with a determination result. Note that, in order
to simplify the description, an effective value of the phase
voltage is referred to as a “phase voltage” in the following20
description.
[0029] Here, a method will be described in which the
inverter control unit 50a calculates each phase voltage of
the three-phase AC voltage on the basis of the DC voltage
value and the zero-cross point.25
[0030] The phase voltages VL1, VL2 and VL3 of three-phase
AC and line voltages VL1-L2, VL2-L3 and VL3-L1 have a relationship
illustrated in FIG. 5. Here, the line voltage VL1-L2 is a
potential difference between the power supply lines L1 and
L2, the line voltage VL2-L3 is a potential difference between30
the power supply lines L2 and L3, and the line voltage VL3-L1
is a potential difference between the power supply lines L3
and L1. Note that, FIG. 5 is a graph illustrating an example
13
of a relationship between each phase voltage of three-phase
AC and a line voltage.
[0031] In addition, there is a relationship illustrated
in FIG. 6 between the phase voltages VL1, VL2, and VL3 of
three-phase AC and the DC voltage Vdc obtained by rectifying5
these phase voltages. Note that, FIG. 6 is a graph
illustrating an example of a relationship between each phase
voltage of three-phase AC and a DC voltage after rectifying
each phase voltage. As illustrated in FIG. 6, a ripple of
the DC voltage Vdc is generated by an influence of each phase10
voltage, and each ripple peaks at a timing when each phase
voltage crosses zero. The peak at the timing of the phase
voltage VL1=0 is caused by an influence of the phase voltages
VL2 and VL3, and the DC voltage Vdc (peak value) at this timing
can be regarded as equal to the line voltage VL2-L3. Similarly,15
the peak at the timing of the phase voltage VL2=0 is caused
by an influence of the phase voltages VL3 and VL1, and the DC
voltage Vdc (peak value) at this timing can be regarded as
equal to the line voltage VL3-L1. The peak at the timing of
the phase voltage VL3=0 is caused by an influence of the20
phase voltages VL1 and VL2, and the DC voltage Vdc (peak value)
at this timing can be regarded as equal to the line voltage
VL1-L2. Note that, the peak value of which ripple of the DC
voltage Vdc corresponds to which line voltage can be derived
from a relationship between phase voltages as long as the25
zero-cross point of any one phase of the three-phase AC is
known. Therefore, the zero-cross point detecting unit 60 of
the electric motor drive device 100a detects the zero-cross
point of one phase.
[0032] Using such a relationship, the inverter control30
unit 50a calculates each phase voltage of the three-phase AC
voltage by the following method.
[0033] First, the inverter control unit 50a calculates a
14
phase A illustrated in FIG. 7, that is, a phase A of the
phase voltage VL1 at the zero-cross point of the phase voltage
VL3. Note that, since the phase voltage VL3=0 is satisfied
at the zero-cross point of the phase voltage VL3, the DC
voltage Vdc at this time depends on the phase voltages VL15
and VL2, and the DC voltage Vdc=line voltage VL1-L2 is
established. FIG. 7 is a graph illustrating a relationship
between the DC voltage Vdc and the line voltage VL1-L2 at the
zero-cross point of the phase voltage VL3.
[0034] Next, the inverter control unit 50a obtains an10
intersection L1 illustrated in FIG. 7. Specifically, the
inverter control unit 50a obtains coordinates (x, y) of the
intersection L1 of two lines obtained by substituting the
calculated phase A into the following Formulas (1) and (2).
[0035] y=tan(A)×x...(1)15
y=tan(120°-A)×x+Vdc...(2)
[0036] Next, the inverter control unit 50a substitutes
the phase A into the following Formula (3) to obtain x at
the intersection L1 illustrated in FIG. 7, and further
substitutes the obtained x into Formula (1) to obtain y.20
[0037] x=Vdc/(tan(A)+tan(120°-A))...(3)
[0038] Next, the inverter control unit 50a substitutes x
and y obtained above into the following Formula (4) to obtain
the phase voltage VL1.
[0039] VL1=√(x^2+y^2)...(4)25
[0040] In addition, the inverter control unit 50a obtains
the phase voltage VL2 by using the phase A and the phase
voltage VL1 obtained above and the following Formulas (5) and
(6).
[0041] Vdc=VL1×sin(A)-VL2×sin(A-120°)...(5)30
VL2=(VL1×sin(A)-Vdc)/sin(A-120°)...(6)
[0042] The inverter control unit 50a obtains the phase
voltage VL3 by a similar method. Specifically, the inverter
15
control unit 50a calculates a phase B of the phase voltage
VL1 at a zero-cross point of the phase voltage VL2, and obtains
the phase voltage VL3 by using the calculated phase B, the
phase voltage VL1, and the following Formulas (7) and (8).
[0043] Vdc=VL3×sin(B-240°)-VL1×sin(B)...(7)5
VL3=(VL1×sin(B)-Vdc)/sin(B-240°)...(8)
[0044] Note that, in the present embodiment, the zero-
cross point detecting unit 60 detects the zero-cross point
of the phase voltage of any one phase of the three-phase AC
voltage, but the inverter control unit 50a may have a10
function of detecting the zero-cross point. That is, means
(for example, a voltage sensor) for detecting an
instantaneous value of the phase voltage of any one phase of
the three-phase AC voltage may be provided, and the inverter
control unit 50a may detect the zero-cross point on the basis15
of a detection result.
[0045] Next, an operation of the electric motor drive
device 100a according to the present embodiment will be
described. FIG. 8 is a flowchart illustrating an example of
an operation of the electric motor drive device 100a20
according to the second embodiment. In FIG. 8, step numbers
identical to those in FIG. 2 indicate identical processing.
The description of the processing with step numbers identical
to those in FIG. 2 will be omitted.
[0046] After the inverter control unit 50a acquires the25
DC voltage value in step S1, the zero-cross point detecting
unit 60 detects a zero-cross point of the phase voltage VL1
(step S11). Next, the inverter control unit 50a calculates
the above-described phase A on the basis of the zero-cross
point detected by the zero-cross point detecting unit 6030
(step S12).
[0047] Next, the inverter control unit 50a calculates
each phase voltage of three-phase AC on the basis of the
16
phase A and a maximum value of the DC voltage Vdc detected
by the voltage detecting unit 40 (step S13). Here, the
maximum value of the DC voltage Vdc is a peak voltage of each
ripple of the DC voltage Vdc. The inverter control unit 50a
calculates each phase voltage (VL1, VL2, VL3) by the method5
described above.
[0048] Next, the inverter control unit 50a checks whether
or not a difference between the individual phase voltages of
the three-phase AC is larger than a predetermined imbalance
detection threshold (step S14). Note that, the imbalance10
detection threshold used in step S14 is different from the
imbalance detection threshold used in step S3 illustrated in
FIG. 2 described in the first embodiment. In step S14, the
inverter control unit 50a calculates a difference between
the phase voltages VL1 and VL2, a difference between the phase15
voltages VL2 and VL3, and a difference between the phase
voltages VL3 and VL1. When one or more of the calculated
differences is larger than the imbalance detection threshold,
the inverter control unit 50a determines that the three-
phase AC voltage is in an imbalanced state (step S14: Yes),20
and reduces an output of the inverter 20 (step S4). When
all of the calculated differences are equal to or smaller
than the imbalance detection threshold, the inverter control
unit 50a determines that the three-phase AC voltage is not
in an imbalanced state (step S14: No), and continues the25
normal operation of the inverter 20 (step S5).
[0049] As described above, the electric motor drive
device 100a according to the present embodiment includes:
the voltage detecting unit 40 which detects a DC voltage
between the three-phase diode bridge 10 and the DC reactor30
30; the zero-cross point detecting unit 60 which monitors
any one phase of the three-phase AC voltage input from the
power supply 1 and detects a zero-cross point of the voltage;
17
and the inverter control unit 50a which calculates a phase
voltage (effective value) of the three-phase AC voltage on
the basis of the DC voltage detected by the voltage detecting
unit 40 and the zero-cross point detected by the zero-cross
point detecting unit 60, and detects an imbalanced state of5
the three-phase AC voltage on the basis of a difference
between the phase voltages. When the inverter control unit
50a detects the imbalanced state of the three-phase AC
voltage, the inverter control unit 50a reduces the output of
the inverter 20. According to the present embodiment, it is10
possible to achieve the electric motor drive device 100a
capable of preventing a defect such as breaker trip and a
failure of a component mounted on the substrate when an
imbalance of the three-phase AC voltage occurs, and it is
possible to achieve downsizing of the device. In addition,15
since the phase voltage of the three-phase AC voltage is
calculated and whether or not to be in an imbalanced state
is determined on the basis of the phase voltage, the
imbalanced state can be accurately detected.
[0050] Third Embodiment.20
In a third embodiment, an application example of the
electric motor drive devices 100 and 100a described in the
first embodiment and the second embodiment will be described.
[0051] FIG. 9 is a diagram illustrating an exemplary
configuration of an air conditioner 200 according to the25
third embodiment. The air conditioner 200 illustrated in
FIG. 9 is implemented by applying the electric motor drive
device 100 described in the first embodiment. The air
conditioner 200 is an example of a refrigeration cycle device
implemented by applying the electric motor drive device 100.30
Note that, the electric motor drive device 100 may be
replaced with the electric motor drive device 100a described
in the second embodiment.
18
[0052] The air conditioner 200 includes the electric
motor drive device 100 connected to the power supply 1 which
outputs three-phase AC power, a compressor 71, a four-way
valve 72, an outdoor heat exchanger 73, an expansion valve
74, an indoor heat exchanger 75, and a refrigerant pipe 76.5
The compressor 71 includes the motor 2 which is driven by
three-phase AC power supplied from the electric motor drive
device 100, and a compression mechanism 77 which compresses
a refrigerant. The motor 2 operates the compression
mechanism 77.10
[0053] The refrigerant circulates through the compressor
71, the four-way valve 72, the outdoor heat exchanger 73,
the expansion valve 74, the indoor heat exchanger 75, and
the refrigerant pipe 76, to form a refrigeration cycle.
[0054] The air conditioner 200 is not limited to a15
separate air conditioner in which an outdoor unit is
separated from an indoor unit, and may be an integrated air
conditioner in which the compressor 71, the indoor heat
exchanger 75, and the outdoor heat exchanger 73 are provided
in one housing.20
[0055] Note that, although the air conditioner 200 has
been described as an example of the refrigeration cycle
device including the electric motor drive device 100, the
refrigeration cycle device is not limited to the air
conditioner 200, and may be a refrigerator, a heat pump hot25
water supply device, or the like.
[0056] In addition, in the present embodiment, the
exemplary configuration has been described in which the motor
2 is applied to a drive source of the compressor 71 and the
motor 2 is driven by the electric motor drive device 100.30
However, the motor 2 driven by the electric motor drive
device 100 may be applied as a drive source for driving an
indoor unit blower and an outdoor unit blower (not
19
illustrated) included in the air conditioner 200. In
addition, the motor 2 driven by the electric motor drive
device 100 may be applied as a drive source of each of the
indoor unit blower, the outdoor unit blower, and the
compressor 71.5
[0057] As described above, the air conditioner 200
according to the present embodiment can detect a voltage
imbalance of the power supply 1 without being affected by a
fluctuation of a load connected to the inverter 20, by using
the electric motor drive device 100 according to the first10
embodiment or the electric motor drive device 100a according
to the second embodiment. In addition, when the voltage
imbalance is detected, the output of the inverter 20 is
reduced, and it is possible to prevent a defect such as
breaker trip and a failure of a component mounted on the15
substrate. Accordingly, reliability and product life of the
air conditioner 200 can be maintained. Even when the
electric motor drive device 100 or 100a described in the
first or second embodiment is applied to a refrigeration
cycle device other than the air conditioner 200, effects20
similar to those of the air conditioner 200 can be obtained.
[0058] The configurations illustrated in the above
embodiments illustrate one example and can be combined with
another known technique, and it is also possible to combine
embodiments with each other and omit and change a part of25
the configuration without departing from the subject matter
of the present disclosure.
Reference Signs List
[0059] 1 power supply; 2 motor; 3 electrolytic30
capacitor; 10 three-phase diode bridge; 20 inverter; 30
DC reactor; 40 voltage detecting unit; 50, 50a inverter
control unit; 60 zero-cross point detecting unit; 71
20
compressor; 72 four-way valve; 73 outdoor heat exchanger;
74 expansion valve; 75 indoor heat exchanger; 76
refrigerant pipe; 77 compression mechanism; 100, 100a
electric motor drive device; 200 air conditioner.
5
21
WE CLAIM:
[Claim 1] An electric motor drive device (100a) comprising:
a three-phase diode bridge (10) to rectify a three-
phase alternating-current (AC) voltage, to convert the AC5
voltage into a direct-current (DC) voltage;
a smoothing capacitor (3) to smooth the DC voltage;
a DC reactor (30) provided between the three-phase diode
bridge (10) and the smoothing capacitor (3);
an inverter (20) to convert the DC voltage smoothed by10
the smoothing capacitor (3) into an AC voltage, and output
the AC voltage to a motor;
a voltage detecting unit(40) to detect a DC voltage
output from the three-phase diode bridge (10);
an inverter control unit (50a) to detect an imbalanced15
state of the three-phase AC voltage based on a DC voltage
value, and control the inverter (20) based on a detection
result of the imbalanced state, the DC voltage value being
a detection value of the DC voltage obtained by the voltage
detecting unit (40), and20
a zero-cross point detecting unit (60) to detect a zero-
cross point of any one phase of the three-phase AC voltage,
wherein
the inverter control unit (50a) detects an imbalanced
state of the three-phase AC voltage based on the DC voltage25
value and the zero-cross point detected by the zero-cross
point detecting unit (60).
[Claim 2] The electric motor drive device (100a) according
to claim 1, wherein30
when the inverter control unit (50a) detects an
imbalanced state of the three-phase AC voltage, the inverter
control unit (50a) reduces an output of the inverter so as
22
to make the output smaller than when the three-phase AC
voltage is in a normal state.
[Claim 3] The electric motor drive device (100a) according
to claim 1, wherein5
the inverter control unit (50a) detects a vertex of a
ripple included in a DC voltage output from the three-phase
diode bridge (10) based on the DC voltage value, and
determines that the three-phase AC voltage is in an
imbalanced state when a difference between vertices of10
adjacent ripples is larger than a predetermined threshold.
[Claim 4] The electric motor drive device (100a) according
to any one of claims 1 to 3, wherein
the inverter control unit (50a) detects a vertex of a15
ripple included in a DC voltage output from the three-phase
diode bridge (10) based on the DC voltage value, calculates
a voltage of each phase of the three-phase AC voltage based
on the detected vertex and the zero-cross point, and compares
the calculated voltages of individual phases to detect an20
imbalanced state of the three-phase AC voltage.
[Claim 5] An air conditioner (200) comprising:
the electric motor drive device(100a) according to any
one of claims 1 to 4, wherein25
the electric motor drive device (100a) generates drive
power for a motor (2) that operates a compression mechanism
(77) that compresses a refrigerant circulating in a
refrigeration cycle.
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