Electric motor drive unit and air conditioning system

Abstract

An electric motor drive device (100) comprising: a three-phase diode bridge (10) that rectifies a three-phase AC voltage and converts it into a DC voltage; an electrolytic capacitor (3) that smoothes a DC voltage; a DC reactor (30) provided between the three-phase diode bridge (10) and the electrolytic capacitor (3); an inverter (20) that converts a DC voltage smoothed by the electrolytic capacitor (3) into an AC voltage and outputs the AC voltage to a motor (2); a voltage detection unit (40) that detects a DC voltage output from the three-phase diode bridge (10);and an inverter control unit (50) that detects an unbalanced state of the three-phase AC voltage based on a DC voltage value that is a detection value of the DC voltage obtained by the voltage detection unit (40), and controls the inverter (20) based on a detection result of the unbalanced state;

Description

Area

[0001] The present disclosure relates to an electric motor driving apparatus and an air conditioner. 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 supply into three-phase AC power with 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 with a configuration including the three-phase diode bridge, when an input three-phase AC voltage is unbalanced, an unbalance in an input current occurs, and pulsation also occurs in a DC voltage after rectification in the three-phase diode bridge. If pulsation in the DC voltage after rectification occurs, there is a possibility of a defect occurring, such as a 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 the three-phase AC current is in an unbalanced state based on a line voltage of a three-phase AC power supply.When the three-phase alternating current is in an unbalanced state, the electric motor drive device protects circuit components by reducing an output of an inverter. List of citationsPatent literature

[0004] Patent Literature 1: Japanese Patent Application Publication No. 2017-22920 Brief description of the inventionProblem to be solved by the invention

[0005] In the conventional electric motor drive device described above, in the processing of determining whether a three-phase alternating current is in an unbalanced state, the line voltage is estimated, and an unbalance rate calculated based on the line voltage estimation result is compared with a predetermined threshold value to detect the unbalanced state. For this reason, in the conventional electric motor drive device, it is necessary to provide a voltage detection circuit for at least two phases of the three-phase alternating current, resulting in an increase in the size of the device, and further complicates processing and increases the processing load. For this reason, it is desirable to obtain an electric motor drive device capable of downsizing the device and reducing the processing load.

[0006] The present disclosure has been made in view of the above, and it is an object of the present disclosure to provide an electric motor driving apparatus capable of achieving downsizing of the apparatus and reduction of the processing load. Means of solving the problem

[0007] To solve the above-mentioned problem and achieve an object, an electric motor drive apparatus according to the present disclosure includes: a three-phase diode bridge for rectifying a three-phase alternating current (AC) voltage to convert the AC voltage into a direct current (DC) voltage; a smoothing capacitor for smoothing the DC voltage; a DC reactor provided between the three-phase diode bridge and the smoothing capacitor; an inverter for converting the DC voltage smoothed by the smoothing capacitor into an AC voltage and outputting the AC voltage to a motor; a voltage detection unit for detecting a DC voltage output from the three-phase diode bridge;and an inverter control unit for detecting an unbalanced state of the three-phase AC voltage based on a DC voltage value and controlling the inverter based on a detection result of the unbalanced state, wherein the DC voltage value is a detection value of the DC voltage obtained by the voltage detection unit; Effects of the invention

[0008] The electric motor driving apparatus according to the present disclosure has the effect of being able to achieve downsizing of the apparatus and reduction of the processing load. Short description of the drawings Fig. 1 is a diagram illustrating an exemplary configuration of an electric motor driving apparatus according to a first embodiment. Fig. 2 is a flowchart illustrating an example of an operation of the electric motor driving apparatus according to the first embodiment. Fig. 3 is a diagram 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 driving apparatus according to a second embodiment. Fig. 5 is a diagram showing an example of a relationship between each phase voltage of a three-phase AC voltage and a line voltage. Fig. 6 is a diagram showing an example of a relationship between each phase voltage of a three-phase AC voltage and a DC voltage after rectifying each phase voltage. Fig. 7 is a diagram illustrating a relationship between a DC voltage and a line voltage at a zero-crossing point of a phase voltage. Fig. 8 is a flowchart illustrating an example of an operation of the electric motor driving apparatus according to the second embodiment. Fig. 9 is a diagram illustrating an exemplary configuration of an air conditioner according to a third embodiment. Description of embodiments

[0009] Hereinafter, an electric motor driving apparatus and an air conditioner according to embodiments of the present disclosure will be described in detail with reference to the drawings. First embodiment

[0010] 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 a three-phase AC power supply from 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 with a desired voltage and frequency to generate drive power for the motor 2. Note that the motor 2 is a three-phase motor.

[0011] The electric motor drive device 100 includes: a three-phase diode bridge 10 that 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 that is a smoothing capacitor for smoothing the DC voltage output from the three-phase diode bridge 10; an inverter 20 that converts the DC voltage smoothed by the electrolytic capacitor 3 into a three-phase AC voltage and applies the three-phase AC voltage to the motor 2; and a DC reactor 30 provided between the three-phase diode bridge 10 and the electrolytic capacitor 3, which reduces a harmonic current contained in a DC current flowing between the three-phase diode bridge 10 and the inverter 20.Further, the electric motor drive device 100 includes: a voltage detection unit 40 connected between the three-phase diode bridge 10 and the DC reactor 30, and detecting the DC voltage output from the three-phase diode bridge 10; and an inverter 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 detection unit 40, and which outputs a command generated based on the input DC voltage value to the inverter 20 to generate drive power for the motor 2. Note that, although in FIG. Fig. 1, the detection value of the voltage output by 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 based on the detection value of the voltage output by the inverter 20, the voltage command, and the DC voltage value described above. The voltage detection unit 40 is implemented, for example, by a voltage sensor. The inverter control unit 50 is implemented, for example, by a microcontroller.

[0012] Although a detailed operation will be described separately, the inverter control unit 50 in the electric motor drive device 100 determines whether the three-phase AC voltage supplied from the power supply 1 is in an unbalanced state or not based on the detection result of the DC voltage obtained by the voltage detection unit 40, and reduces an output of the inverter 20 when the three-phase AC voltage is in the unbalanced state.

[0013] Here, as described above, when there is an imbalance in the input three-phase AC voltage, an imbalance in an input current occurs, and pulsation (hereinafter referred to as ripple) also occurs in the DC voltage rectified by the three-phase diode bridge 10. That is, when the three-phase AC voltage is in an unbalanced 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 control unit 50 of the electric motor drive device 100 according to the present embodiment detects the imbalance of the three-phase AC voltage by utilizing such characteristics.As a result, it is not necessary to provide a circuit for detecting a voltage of each phase of the three-phase alternating current input from the power supply 1, and it is possible to reduce the size and cost of the device.

[0014] 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 drive device 100 is configured to detect the DC voltage between the three-phase diode bridge 10 and the DC reactor 30, where the influence of the load fluctuation is small. Note that a configuration can be adopted in which the DC voltage is detected at a position (for example, between the electrolytic capacitor 3 and the inverter 20) that is different from the 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 compared to the ripple generated with the unbalance of the three-phase AC voltage.

[0015] Fig. 2 is a flowchart illustrating an example of an operation of the electric motor driving apparatus 100 according to the first embodiment. In particular, 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 voltage imbalance and controls the inverter 20 according to the determination result.

[0016] When the electric motor driving device 100 performs the power conversion operation for generating the drive power for the motor 2, the inverter control unit 50 repeats the operation according to the flowchart of Fig. 2. That is, when the electric motor driving device 100 drives the motor 2, the inverter control unit 50 repeatedly executes a series of processing from start to finish in a predetermined cycle, which is shown in Fig. 2 are shown.

[0017] Specifically, the inverter control unit 50 first obtains a DC voltage value (step S1). Specifically, the inverter control unit 50 obtains a detection value of a DC voltage from the voltage detection unit 40.

[0018] Next, the inverter control unit 50 calculates a ripple voltage based on the DC voltage value obtained in step S1 (step S2). The ripple voltage calculated by the inverter control unit 50 in step S2 is calculated with reference to Fig. 3 described. Fig. 3 is a diagram for explaining a ripple voltage calculated by the inverter control unit 50 according to the first embodiment. In Fig. 3, the reference symbol “V dc “ represents a DC voltage detected by the voltage detection unit 40, and the reference symbols “V L1 “, “V L2 ' and 'V L3 “ represent voltages of respective phases of the three-phase alternating current input from the three power supply lines L1 to L3 into the electric motor driving device 100. The horizontal axis represents time, and the vertical axis represents voltage. Fig. 3 shows an example of a correspondence relationship between the DC voltage V dc and the voltages V L1 , V L2 and V L3 of the individual phases of the three-phase alternating voltage. As shown in Fig. As shown in Figure 3, the ripple voltage calculated by the inverter control unit 50 is a difference between the magnitudes of adjacent ripples included in the DC voltage, that is, a voltage difference between adjacent peaks. In step S2, the inverter control unit 50 detects a ripple peak by analyzing the last DC voltage value acquired by the voltage detection unit 40 and a DC voltage value acquired in the past, and calculates the ripple voltage from the detected peak. For example, when the inverter control unit 50 detects the peak of the last ripple by analyzing the DC voltage value, the inverter control unit 50 obtains a difference between the detected peak and the previously detected ripple peak and sets this difference as the ripple voltage.

[0019] 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 the imbalance detection threshold) (step S3). Note that the imbalance detection threshold is determined in advance, for example, by performing an operation simulation of the electric motor drive device 100.

[0020] If the ripple voltage is greater than the imbalance detection threshold (step S3: YES), the inverter control unit 50 determines that the three-phase AC voltage is in an unbalanced 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 in the normal state. Note that N < 100 is satisfied. The normal state is a state in which the three-phase AC voltage is not unbalanced. The N described above can be a variable value. For example, if the ripple voltage and the imbalance detection threshold are very different, N can be changed to 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, and a value of N to be used may be determined based on a comparison result between the ripple voltage and each imbalance detection threshold.

[0021] If the ripple voltage is equal to or less than the imbalance detection threshold (step S3: NO), the inverter control unit 50 determines that the three-phase AC voltage is not in an unbalanced state, that is, it determines that the three-phase AC voltage is in the normal state, and continues normal operation of the inverter 20 (step S5). Note that in normal operation, the inverter control unit 50 performs control so that a voltage output from the inverter 20 follows the voltage command.

[0022] As described above, the electric motor drive apparatus 100 according to the present embodiment includes: the voltage detection unit 40 that detects a DC voltage between the three-phase diode bridge 10 and the DC reactor 30; and the inverter control unit 50 that detects an unbalanced state of the three-phase AC voltage based on a ripple of the DC voltage detected by the voltage detection unit 40. The inverter control unit 50 reduces the output of the inverter 20 upon detecting the unbalanced state of the three-phase AC voltage.According to the present embodiment, it is possible to obtain the electric motor driving apparatus 100 capable of preventing a defect such as circuit breaker tripping and 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 apparatus and reduction of the processing load. Second embodiment

[0023] The electric motor drive apparatus 100 according to the above first embodiment determines whether the three-phase AC voltage is in an unbalanced state or not by comparing a predetermined unbalance detection threshold and a ripple voltage calculated based on a DC voltage detected by the voltage detection unit 40 provided between the three-phase diode bridge 10 and the DC reactor 30. On the other hand, in the present embodiment, an electric motor drive apparatus 100a capable of accurately detecting an unbalance even in the case of a large fluctuation in a DC voltage due to an influence of a fluctuation in a load connected to the inverter 20 is described.

[0024] Fig. 4 is a diagram illustrating an exemplary configuration of the electric motor driving apparatus 100a according to a second embodiment. In Fig. 4 are components similar to those of the electric motor drive device 100 according to the Fig. 1 shown first embodiment are designated by identical reference numerals. The description of the components designated by reference numerals that are identical to those in Fig. 1 are identical, is omitted.

[0025] The electric motor drive apparatus 100a has a configuration in which the inverter control unit 50 of the electric motor drive apparatus 100 according to the first embodiment is replaced with an inverter control unit 50a and a zero-crossing point detection unit 60 is added.

[0026] The zero-cross point detection unit 60 monitors any phase of a three-phase alternating voltage input from the power supply 1 to the electric motor drive device 100a, detects a zero-cross point of the voltage, and outputs a detection result to the inverter control unit 50a. Fig. 4, the zero-crossing point detection unit 60 detects a zero-crossing point of the voltage V L1 the power supply line L1. The zero-crossing point detection unit 60 is implemented, for example, by a voltage sensor, a logic circuit that determines a sign of a voltage detection value obtained by the voltage sensor, and the like.

[0027] The inverter control unit 50a generates a command to the inverter 20 based on the DC voltage value detected by the voltage detection unit 40 and the zero-crossing point detected by the zero-crossing point detection unit 60. Specifically, the inverter control unit 50a calculates a voltage (hereinafter, a voltage of one phase is referred to as a phase voltage) of each phase of the three-phase AC voltage input to the electric motor drive device 100a based on the DC voltage value and the zero-crossing point. Then, the inverter control unit 50a determines whether the three-phase AC voltage is in an unbalanced state based on the calculated effective value of each phase voltage, and controls the output of the inverter 20 according to a determination result.It should be noted that, to simplify the description, an effective value of the phase voltage is referred to as “phase voltage” in the following description.

[0028] Here, a method is described in which the inverter control unit 50a calculates each phase voltage of the three-phase AC voltage based on the DC voltage value and the zero-crossing point.

[0029] The phase voltages V L1 , V L2 and V L3 the three-phase alternating voltage and the line voltages V L1-L2 , V L2-L3 and V L3-L1 have a Fig. 5. The line voltage V L1-L2 a potential difference between the power supply lines L1 and L2, is the line voltage V L2-L3 a potential difference between the power supply lines L2 and L3 and is the line voltage V L3-L1a potential difference between the power supply lines L3 and L1. It should be noted that Fig. 5 is a diagram showing an example of a relationship between each phase voltage of a three-phase AC voltage and a line voltage.

[0030] In addition, there is a Fig. 6 shows the relationship between the phase voltages V L1 , V L2 and V L3 the three-phase alternating voltage and the direct voltage V obtained by rectifying these phase voltages dc . It should be noted that Fig. 6 is a diagram showing an example of a relationship between each phase voltage of a three-phase AC voltage and a DC voltage after rectifying each phase voltage. As shown in Fig. 6, a ripple of the DC voltage V dcgenerated by the influence of each phase voltage, and each ripple reaches its peak at the time when each phase voltage crosses zero. The peak at the time of the phase voltage V L1 = 0 is caused by an influence of the phase voltages V L2 and V L3 caused, and the DC voltage V dc (peak value) at this time can be considered equal to the line voltage V L2-L3 Similarly, the peak at the time of the phase voltage V L2 = 0 due to the influence of the phase voltages V L3 and V L1 caused, and the DC voltage V dc (peak value) at this time can be considered equal to the line voltage V L3-L1 The peak at that time of the phase voltage V L3 = 0 is caused by an influence of the phase voltages V L1 and V L2caused, and the DC voltage V dc (peak value) at this time can be considered equal to the line voltage V L1-L2 It should be noted that the maximum value whose ripple of the DC voltage V dc The zero-crossing point corresponding to the line voltage can be derived from a relationship between phase voltages as long as the zero-crossing point of any phase of the three-phase AC voltage is known. Therefore, the zero-crossing point detection unit 60 of the electric motor drive device 100a detects the zero-crossing point of a phase.

[0031] Using such a relationship, the inverter control unit 50a calculates each phase voltage of the three-phase AC voltage by the following method.

[0032] First, the inverter control unit 50a calculates a Fig. 7 shown phase A, that is, a phase A of the phase voltage V L1at the zero crossing point of the phase voltage V L3 . It should be noted that since the phase voltage V L3 = 0 at the zero crossing point of the phase voltage V L3 is fulfilled, the DC voltage V dc at this time from the phase voltages V L1 and V L2 depends, and the DC voltage V dc = Line voltage V L1-L2 is formed. Fig. Figure 7 is a diagram showing a relationship between the DC voltage V dc and the line voltage V L1-L2 at the zero crossing point of the phase voltage V L3 represents.

[0033] Next, the inverter control unit 50a determines a Fig. 7. Specifically, the inverter control unit 50a determines coordinates (x, y) of the intersection point L1 of two lines, which are obtained by substituting the calculated phase A in the following formulas (1) and (2). y=tan(A)×x y=tan(120°−A)×x+Vdc

[0034] Next, the inverter control unit 50a substitutes the phase A in the following formula (3) to set x at the value shown in Fig. 7, and further substitutes the obtained x in formula (1) to obtain y. x=Vdc / (tan(A)+tan(120°−A))

[0035] Next, the inverter control unit 50a substitutes the x and y obtained above in the following formula (4) to obtain the phase voltage V L1 to obtain. VL1=√(x2+y2)

[0036] In addition, the inverter control unit 50a determines the phase voltage V L2 using phase A and the phase voltage V obtained above L1 and the following formulas (5) and (6). Vdc=VL1×sin(A)−VL2×sin(A−120°) VL2=(VL1×sin(A)−Vdc) / sin(A−120°)

[0037] The inverter control unit 50a receives the phase voltage V L3 by a similar method. Specifically, the inverter control unit 50a calculates a phase B of the phase voltage V L1 at a zero crossing point of the phase voltage V L2 and receives the phase voltage V L3 using the calculated phase B, the phase voltage V L1 and the following formulas (7) and (8). Vdc=VL3×sin(B−240°)−VL1×sin(B) VL3=(VL1×sin(B)−Vdc) / sin(B−240°)

[0038] Note that in the present embodiment, the zero-crossing point detection unit 60 detects the zero-crossing point of the phase voltage of any phase of the three-phase AC voltage, but the inverter control unit 50a may have a function for detecting the zero-crossing point. That is, a means (for example, a voltage sensor) for detecting an instantaneous value of the phase voltage of any phase of the three-phase AC voltage may be provided, and the inverter control unit 50a may detect the zero-crossing point based on the detection result.

[0039] Next, an operation of the electric motor driving apparatus 100a according to the present embodiment will be described. Fig. 8 is a flowchart illustrating an example of an operation of the electric motor driving apparatus 100a according to the second embodiment. In Fig. 8 give step numbers that correspond to those in Fig. 2 are identical, identical processing is required. The description of the processing with step numbers that correspond to those in Fig. 2 are identical, is omitted.

[0040] After the inverter control unit 50a acquires the DC voltage value in step S1, the zero-crossing point detection unit 60 detects a zero-crossing point of the phase voltage V L1 (Step S11). Next, the inverter control unit 50a calculates the above-described phase A based on the zero-crossing point detected by the zero-crossing point detection unit 60 (Step S12).

[0041] Next, the inverter control unit 50a calculates each phase voltage of the three-phase AC voltage based on the phase A and a maximum value of the DC voltage V detected by the voltage detection unit 40 dc (Step S13). Here, the maximum value of the DC voltage V dca peak voltage of a respective ripple of the DC voltage V dc . The inverter control unit 50a calculates each phase voltage (V L1 , V L2 , V L3 ) using the procedure described above.

[0042] Next, the inverter control unit 50a checks whether a difference between the individual phase voltages of the three-phase AC voltage is greater than a predetermined imbalance detection threshold (step S14). Note that the imbalance detection threshold used in step S14 is different from the imbalance detection threshold used in step S3, which is Fig. 2 described in the first embodiment. In step S14, the inverter control unit 50a calculates a difference between the phase voltages V L1 and V L2 , a difference between the phase voltages V L2and V L3 and a difference between the phase voltages V L3 and V L1 If one or more of the calculated differences is / are greater than the imbalance detection threshold, the inverter control unit 50a determines that the three-phase AC voltage is in an unbalanced state (step S14: YES) and reduces an output of the inverter 20 (step S4). If all of the calculated differences are equal to or less than the imbalance detection threshold, the inverter control unit 50a determines that the three-phase AC voltage is not in an unbalanced state (step S14: NO) and continues normal operation of the inverter 20 (step S5).

[0043] As described above, the electric motor drive device 100a according to the present embodiment includes: the voltage detection unit 40 that detects a DC voltage between the three-phase diode bridge 10 and the DC reactor 30; the zero-crossing point detection unit 60 that monitors any phase of the three-phase AC voltage input from the power supply 1 and detects a zero-crossing point of the voltage; and the inverter control unit 50a that calculates a phase voltage (effective value) of the three-phase AC voltage based on the DC voltage detected by the voltage detection unit 40 and the zero-crossing point detected by the zero-crossing point detection unit 60, and detects an unbalanced state of the three-phase AC voltage based on a difference between the phase voltages.When the inverter control unit 50a detects the unbalanced 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 is possible to obtain the electric motor drive device 100a capable of preventing a defect such as circuit breaker tripping and failure of a component mounted on the substrate when an unbalanced state of the three-phase AC voltage occurs, and it is possible to achieve downsizing of the device. In addition, since the phase voltage of the three-phase AC voltage is calculated and whether or not an unbalanced state exists is determined based on the phase voltage, the unbalanced state can be accurately detected. Third embodiment

[0044] In a third embodiment, an application example of the electric motor driving apparatuses 100 and 100a described in the first embodiment and the second embodiment will be described.

[0045] Fig. 9 is a diagram illustrating an exemplary configuration of an air conditioner 200 according to the third embodiment. Fig. The air conditioner 200 shown in FIG. 9 is implemented by using 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 using the electric motor drive device 100. Note that the electric motor drive device 100 can be replaced with the electric motor drive device 100a described in the second embodiment.

[0046] The air conditioner 200 includes the electric motor drive unit 100 connected to the power supply 1, which outputs three-phase alternating current, 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 line 76. The compressor 71 includes the motor 2 driven by the three-phase alternating current supplied from the electric motor drive unit 100, and a compression mechanism 77 that compresses a refrigerant. The motor 2 drives the compression mechanism 77.

[0047] 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 line 76 to form a refrigeration cycle.

[0048] The air conditioner 200 is not limited to a 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 a single housing.

[0049] 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 hot water supply device, or the like.

[0050] Additionally, in the present embodiment, the exemplary configuration in which the motor 2 is used as a drive source of the compressor 71, and the motor 2 is driven by the electric motor drive device 100, has been described. However, the motor 2 driven by the electric motor drive device 100 can be used as a drive source for driving an indoor unit fan and an outdoor unit fan (not shown) included in the air conditioner 200. In addition, the motor 2 driven by the electric motor drive device 100 can be used as a drive source of each of the indoor unit fan, the outdoor unit fan, and the compressor 71.

[0051] As described above, by using the electric motor drive device 100 according to the first embodiment or the electric motor drive device 100a according to the second embodiment, 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. 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 a circuit breaker trip and a failure of a component mounted on the substrate. Accordingly, the reliability and product life of the air conditioner 200 can be maintained.Even if the electric motor driving apparatus 100 or 100a described in the first or second embodiment is applied to a refrigeration cycle apparatus other than the air conditioner 200, effects similar to those in the air conditioner 200 can be obtained.

[0052] The configurations shown in the above embodiments are an example and can be combined with other known techniques, and it is also possible to combine embodiments with each other and omit and change part of the configuration without departing from the subject matter of the present disclosure. List of reference symbols 1 power supply; 2 engine; 3 electrolytic capacitor; 10 three-phase diode bridge; 20 inverters; 30 DC choke; 40 voltage detection unit; 50, 50a inverter control unit; 60 zero crossing point detection unit; 71 compressors; 72 four-way valve; 73 outdoor heat exchangers; 74 expansion valve; 75 indoor heat exchangers; 76 refrigerant line; 77 compression mechanism; 100, 100a electric motor drive device; 200 air conditioning.

Claims

[1] Electric motor drive device, comprising: a three-phase diode bridge for rectifying a three-phase alternating current (AC) voltage to convert the AC voltage into a direct current (DC) voltage; a smoothing capacitor for smoothing the DC voltage; a DC choke provided between the three-phase diode bridge and the smoothing capacitor; an inverter for converting the DC voltage smoothed by the smoothing capacitor into an AC voltage and outputting the AC voltage to a motor; a voltage detection unit for detecting a DC voltage output from the three-phase diode bridge; and an inverter control unit for detecting an unbalanced state of the three-phase AC voltage based on a DC voltage value and for controlling the inverter based on a detection result of the unbalanced state, wherein the DC voltage value is a detection value of the DC voltage obtained by the voltage detection unit. [2] The electric motor driving apparatus according to claim 1, wherein when the inverter control unit detects an unbalanced state of the three-phase AC voltage, the inverter control unit reduces an output of the inverter to make the output smaller than when the three-phase AC voltage is in a normal state. [3] The electric motor driving apparatus according to claim 1 or 2, wherein the inverter control unit detects a peak of a ripple included in a DC voltage output from the three-phase diode bridge based on the DC voltage value, and determines that the three-phase AC voltage is in an unbalanced state when a difference between peaks of adjacent ripples is greater than a predetermined threshold. [4] Electric motor drive device according to claim 1 or 2, comprising: a zero-crossing point detection unit for detecting a zero-crossing point of any phase of the three-phase alternating voltage, wherein the inverter control unit detects an unbalanced state of the three-phase AC voltage based on the DC voltage value and the zero-crossing point detected by the zero-crossing point detection unit. [5] The electric motor driving apparatus according to claim 4, wherein the inverter control unit detects a peak of a ripple included in a DC voltage output from the three-phase diode bridge based on the DC voltage value, calculates a voltage of each phase of the three-phase AC voltage based on the detected peak and the zero-crossing point, and compares the calculated voltages of individual phases to detect an unbalanced state of the three-phase AC voltage. [6] Air conditioning system, comprising: the electric motor drive device according to one of claims 1 to 5, wherein the electric motor drive unit generates drive power for a motor that operates a compression mechanism that compresses a refrigerant circulating in a refrigeration cycle.

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