Electric motor driving device, and air conditioner

Abstract

An electric motor driving device (100) comprises a three-phase diode bridge (10) that rectifies and converts a three-phase AC voltage into a DC voltage, an electrolytic capacitor (3) that smooths the DC voltage, a DC reactor (30) provided between the three-phase diode bridge (10) and the electrolytic capacitor (3), an inverter (20) that converts the 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 the DC voltage output by the three-phase diode bridge (10), and an inverter control unit (50) that detects an imbalance state of the three-phase AC voltage on the basis of a DC voltage value, which is a value of the DC voltage detected by the voltage detection unit (40), and controls the inverter (20) on the basis of the result of detecting the imbalance state.

Description

Electric motor drive device and air conditioner

[0001] The present disclosure relates to an electric motor drive device and an air conditioner.

[0002] There is an electric motor drive device that includes a three-phase AC diode bridge and an inverter, and converts power supplied from a three-phase AC power source into three-phase AC power of a desired voltage and frequency and supplies the power to a motor (see, for example, Patent Document 1).

[0003] In an electric motor drive device having a three-phase diode bridge, if there is an imbalance in the input three-phase AC voltage, an imbalance occurs in the input current, causing pulsation in the DC voltage rectified by the three-phase diode bridge. Pulsation in the rectified DC voltage can cause problems such as breaker tripping and damage to components mounted on the circuit board. To address this problem, the electric motor drive device described in Patent Document 1 determines whether the three-phase AC is unbalanced based on the line voltage of the three-phase AC power supply, and if it is unbalanced, suppresses the inverter output to protect the circuit components.

[0004] JP 2017-22920 A

[0005] In the above-described conventional electric motor drive device, in the process of determining whether the three-phase AC is in an unbalanced state, the device estimates the line voltage, and then compares the unbalance rate calculated based on the estimated line voltage with a predetermined threshold to detect the unbalanced state. Therefore, the conventional electric motor drive device needs to have voltage detection circuits for at least two phases of the three-phase AC, which increases the device size and also complicates the processing, increasing the processing load. For these reasons, it is desirable to realize an electric motor drive device that can be made smaller and has a reduced processing load.

[0006] The present disclosure has been made in view of the above, and has an object to provide an electric motor drive device that can achieve a smaller device size and a reduced processing load.

[0007] In order to solve the above-mentioned problems and achieve the object, the electric motor drive device according to the present disclosure includes a three-phase diode bridge that rectifies a three-phase AC voltage and converts it into a DC voltage, a smoothing capacitor that smooths the DC voltage, a DC reactor provided between the three-phase diode bridge and the smoothing capacitor, an inverter that converts the DC voltage smoothed by the smoothing capacitor into an AC voltage and outputs it to a motor, a voltage detection unit that detects the DC voltage output by the three-phase diode bridge, and an inverter control unit that detects an unbalanced state in the three-phase AC voltage based on the DC voltage value that is the DC voltage detected by the voltage detection unit, and controls the inverter based on the detection result of the unbalanced state.

[0008] The electric motor drive device according to the present disclosure has the effect of realizing a smaller device and a reduced processing load.

[0009] FIG. 1 is a diagram showing an example of the configuration of an electric motor drive device according to a first embodiment; FIG. 2 is a flowchart showing an example of the operation of the electric motor drive device 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 showing an example of the configuration of an electric motor drive device according to a second embodiment; FIG. 5 is a diagram showing an example of the relationship between each phase voltage of a three-phase AC and a line voltage; FIG. 6 is a diagram showing an example of the relationship between each phase voltage of a three-phase AC and a DC voltage after rectifying each phase voltage;

[0010] Hereinafter, an electric motor drive device and an air conditioner according to an embodiment of the present disclosure will be described in detail with reference to the drawings.

[0011] First Embodiment. Fig. 1 is a diagram showing an example of the configuration of an electric motor drive device 100 according to a first embodiment. The electric motor drive device 100 is connected to a power source 1 via three power supply lines L1 to L3, and receives a supply of three-phase AC power from the power source 1 to drive a motor 2. That is, the electric motor drive device 100 converts the three-phase AC power supplied from the power source 1 into three-phase AC power of a desired voltage and frequency, and generates drive power for the motor 2. The motor 2 is a three-phase electric motor.

[0012] The electric motor drive device 100 includes a three-phase diode bridge 10 that rectifies a three-phase AC voltage supplied from a power source 1 that is a three-phase AC power source and converts it into a DC voltage, an electrolytic capacitor 3 that is a smoothing capacitor that smooths the DC voltage output by 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 it to a motor 2, and a DC reactor 30 that is provided between the three-phase diode bridge 10 and the electrolytic capacitor 3 and suppresses harmonic currents contained in the DC current flowing between the three-phase diode bridge 10 and the inverter 20. The electric motor drive device 100 also includes a voltage detection unit 40 that is connected between the three-phase diode bridge 10 and the DC reactor 30 and detects the DC voltage output by the three-phase diode bridge 10, and an inverter control unit 50 that receives a DC voltage value that is the DC voltage detected by the voltage detection unit 40 and generates a command based on the input DC voltage value to the inverter 20, thereby causing the inverter 20 to generate drive power for the motor 2. Although not shown in FIG. 1 , the detected 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 for the inverter 20 based on the detected value of the voltage output by the inverter 20, the voltage command, and the DC voltage value. The voltage detection unit 40 is realized by, for example, a voltage sensor. The inverter control unit 50 is realized by, for example, a microcontroller.

[0013] Although detailed operation will be explained separately, in the electric motor drive device 100, the inverter control unit 50 determines whether the three-phase AC voltage supplied from the power source 1 is in an unbalanced state based on the detection result of the DC voltage by the voltage detection unit 40, and if it is in an unbalanced state, the output of the inverter 20 is suppressed.

[0014] As described above, if there is an imbalance in the input three-phase AC voltage, an imbalance occurs in the input current, and pulsation (hereinafter referred to as ripple) also occurs in the DC voltage rectified by the three-phase diode bridge 10. In other words, when the three-phase AC voltage becomes unbalanced, the ripple component in the DC voltage increases. Therefore, by monitoring the DC voltage rectified by the three-phase diode bridge 10, it is possible to detect the imbalance in the three-phase AC voltage. The inverter control unit 50 of the electric motor drive device 100 according to this embodiment utilizes this characteristic to detect the imbalance in the three-phase AC voltage. This eliminates the need for a circuit to detect the voltage of each phase of the three-phase AC input from the power source 1, thereby enabling the device to be made smaller and less expensive.

[0015] Furthermore, since fluctuations in the load of inverter 20 to which DC voltage is applied also cause DC voltage ripples, motor drive device 100 is configured to detect the DC voltage between three-phase diode bridge 10, which is less affected by load fluctuations, and DC reactor 30. Note that if the expected maximum fluctuation in the load connected to inverter 20 is small, that is, if ripples generated due to load fluctuations are negligibly small compared to ripples generated due to imbalance in the three-phase AC voltage, the DC voltage may be detected at a location different from the DC voltage detection location shown in Fig. 1 (for example, between electrolytic capacitor 3 and inverter 20).

[0016] Fig. 2 is a flowchart showing an example of the operation of the electric motor drive device 100 according to the first embodiment. Specifically, the flowchart in Fig. 2 shows an example of the operation in which the inverter control unit 50 of the electric motor drive device 100 determines whether or not there is an imbalance in the power supply voltages, and controls the inverter 20 in accordance with the determination result.

[0017] When the electric motor drive device 100 is performing a power conversion operation to generate 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 drive device 100 drives the motor 2, the inverter control unit 50 repeatedly executes the series of processes from start to end shown in Fig. 2 at a predetermined cycle.

[0018] Specifically, the inverter control unit 50 first acquires the DC voltage value (step S1). More specifically, the inverter control unit 50 acquires the detected value of the DC voltage from the voltage detection unit 40.

[0019] Next, the inverter control unit 50 calculates a ripple voltage based on 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 diagram for explaining the ripple voltage calculated by the inverter control unit 50 according to the first embodiment. In FIG. 3, V dc indicates the DC voltage detected by the voltage detection unit 40, and V L1 , V L2 and V L3 indicates the voltage of each phase of the three-phase AC input from each of the three power supply lines L1 to L3 to the electric motor drive device 100. The horizontal axis indicates time and the vertical axis indicates voltage. L1 , V L2 and V L3 and DC voltage V dc 3 shows an example of a correspondence relationship between the ripple voltage and the DC voltage. As shown in FIG. 3, the ripple voltage calculated by the inverter control unit 50 is the difference in magnitude between adjacent ripples contained in the DC voltage, i.e., the voltage difference between adjacent peaks. In step S2, the inverter control unit 50 detects the peaks of the ripples by analyzing the latest DC voltage value acquired from the voltage detection unit 40 and previously acquired DC voltage values, and calculates the ripple voltage from the detected peaks. For example, when the inverter control unit 50 analyzes the DC voltage value and detects the latest ripple peak, it calculates the difference between the detected peak and the peak of the ripple detected previously, and sets this difference as the ripple voltage.

[0020] Next, the inverter control unit 50 compares the ripple voltage calculated in step S2 with a predetermined threshold value for detecting unbalance (hereinafter referred to as the unbalance detection threshold value) (step S3). The unbalance detection threshold value is determined in advance by, for example, performing an operational simulation of the electric motor drive device 100.

[0021] If the ripple voltage is greater than the unbalance detection threshold (step S3: Yes), the inverter control unit 50 determines that the three-phase AC voltage is unbalanced and suppresses the output of the inverter 20 (step S4). For example, the inverter control unit 50 controls the inverter 20 so that the maximum output of the inverter 20 does not exceed N% of the maximum output in normal operation. Note that N<100, and normal operation refers to a state in which the three-phase AC voltage is not unbalanced. The above-mentioned N may be a variable value. For example, if the ripple voltage and the unbalance detection threshold differ significantly, N may be changed to a smaller value. Alternatively, multiple different unbalance detection thresholds and values ​​of N corresponding to each unbalance detection threshold may be prepared, and the value of N to be used may be determined based on the results of comparing the ripple voltage with each unbalance detection threshold.

[0022] If the ripple voltage is equal to or less than the unbalance 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, that the three-phase AC voltage is in a normal state, and continues normal operation of the inverter 20 (step S5). Note that in the case of normal operation, the inverter control unit 50 controls the voltage output by the inverter 20 so that it follows the voltage command.

[0023] As described above, the electric motor drive device 100 according to this embodiment includes the voltage detection unit 40 that detects the 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 the ripple of the DC voltage detected by the voltage detection unit 40, and when the inverter control unit 50 detects an unbalanced state of the three-phase AC voltage, it suppresses the output of the inverter 20. According to this embodiment, it is possible to realize the electric motor drive device 100 that can prevent malfunctions such as breaker tripping and damage to components mounted on the board when an imbalance in the three-phase AC voltage occurs, and it is also possible to reduce the size of the device and the processing load.

[0024] Second Embodiment The electric motor drive device 100 according to the first embodiment determines whether the three-phase AC voltage is in an unbalanced state by comparing a ripple voltage calculated based on the DC voltage detected by a voltage detection unit 40 provided between the three-phase diode bridge 10 and the DC reactor 30 with a predetermined unbalance detection threshold. In contrast, in the present embodiment, an electric motor drive device 100a will be described that can accurately detect unbalance even when there is large fluctuation in the DC voltage due to the influence of fluctuations in the load connected to the inverter 20.

[0025] Fig. 4 is a diagram showing an example of the configuration of an electric motor drive device 100a according to the second embodiment. In Fig. 4, the same components as those in the electric motor drive device 100 according to the first embodiment shown in Fig. 1 are denoted by the same reference numerals. Explanation of the components denoted by the same reference numerals as those in Fig. 1 will be omitted.

[0026] The electric motor driving device 100a has a configuration in which the inverter control unit 50 of the electric motor driving device 100 according to the first embodiment is replaced with an inverter control unit 50a, and a zero-cross detection unit 60 is added.

[0027] The zero-cross detector 60 monitors one of the three-phase AC voltages input from the power supply 1 to the motor drive device 100a, detects the zero-cross points of the voltage, and outputs the detection result to the inverter control unit 50a. In the configuration shown in FIG. 4, the zero-cross detector 60 detects the voltage V L1 The zero-crossing detection unit 60 is realized by, for example, a voltage sensor and a logic circuit that determines the sign of the voltage detected by the voltage sensor.

[0028] The inverter control unit 50a generates a command for the inverter 20 based on the DC voltage value detected by the voltage detection unit 40 and the zero-crossing points detected by the zero-crossing detection unit 60. Specifically, the inverter control unit 50a calculates the voltage of each phase of the three-phase AC voltage input to the electric motor drive device 100a (hereinafter, the voltage of one phase will be referred to as a phase voltage) based on the DC voltage value and the zero-crossing points. The inverter control unit 50a then determines whether the three-phase AC voltage is in an unbalanced state based on the calculated effective values ​​of the phase voltages, and controls the output of the inverter 20 in accordance with the determination result. For simplicity of explanation, the effective values ​​of the phase voltages will be referred to as "phase voltages" in the following explanation.

[0029] Here, a method for the inverter control unit 50a to calculate each phase voltage of the three-phase AC voltage based on the DC voltage value and the zero crossing point will be described.

[0030] Three-phase AC phase voltage V L1 , V L2 and V L3 and line voltage V L1-L2 , V L2-L3 and V L3-L1 The relationship between the line voltage V and the L1-L2 is the potential difference between the power supply lines L1 and L2, and the line voltage V L2-L3 is the potential difference between the power supply lines L2 and L3, and the line voltage V L3-L1 is the potential difference between the power supply lines L3 and L1. Note that Fig. 5 is a diagram showing an example of the relationship between each phase voltage of a three-phase AC and the line voltage.

[0031] Also, the phase voltage V of the three-phase AC L1 , V L2 and V L3 and the DC voltage V obtained by rectifying these phase voltages. dc There is a relationship shown in FIG. 6 between the DC voltage V and the DC voltage V after rectification. FIG. 6 is a diagram showing an example of the relationship between each phase voltage of a three-phase AC and the DC voltage V after rectification. As shown in FIG. 6, dc The ripples in are generated by the influence of each phase voltage, and each ripple reaches its peak when each phase voltage crosses zero. L1 The peak at the timing when = 0 is the phase voltage V L2and V L3 This is due to the influence of the DC voltage V dc (peak value) is the line voltage V L2-L3 Similarly, the phase voltage V L2 The peak at the timing when = 0 is the phase voltage V L3 and V L1 This is due to the influence of the DC voltage V dc (peak value) is the line voltage V L3-L1 Phase voltage V L3 The peak at the timing when = 0 is the phase voltage V L1 and V L2 This is due to the influence of the DC voltage V dc (peak value) is the line voltage V L1-L2 It can be considered to be the same as the DC voltage V dc The correspondence between the peak value of the ripple and the line voltage can be determined from the relationship between the phase voltages if the zero-crossing point of any one of the three-phase AC is known. Therefore, the zero-crossing detector 60 of the electric motor drive device 100a detects the zero-crossing point of one phase.

[0032] Using this relationship, the inverter control unit 50a calculates each phase voltage of the three-phase AC voltage in the following manner.

[0033] The inverter control unit 50a first calculates the phase A shown in FIG. 7, that is, the phase voltage V L3 Phase voltage V at the zero crossing point L1 The phase A of the phase voltage V L3 At the zero crossing point of the phase voltage V L3 = 0, so the DC voltage V dc is the phase voltage V L1 and V L2 depends on the DC voltage V dc = Line voltage V L1-L2 The phase voltage V L3 DC voltage V at the zero crossing point dc and line voltage V L1-L2 FIG.

[0034] Next, the inverter control unit 50a determines the intersection L1 shown in Fig. 7. Specifically, the inverter control unit 50a determines the coordinates (x, y) of the intersection L1 of the two lines obtained by substituting the calculated phase A into the following equations (1) and (2).

[0035] y=tan(A)×x…(1) y=tan(120°−A)×x+V dc …(2)

[0036] Next, the inverter control unit 50a substitutes the phase A into the following equation (3) to find x at the intersection L1 shown in FIG. 7, and then substitutes the found x into equation (1) to find y.

[0037] x = V dc / (tan(A)+tan(120°-A))…(3)

[0038] Next, the inverter control unit 50a substitutes the calculated x and y into the following equation (4) to obtain the phase voltage V L1 Ask for.

[0039] V L1 =√(x^2+y^2) …(4)

[0040] Furthermore, the inverter control unit 50a calculates the phase A and the phase voltage V L1 and the phase voltage V L2 Ask for.

[0041] V dc =V L1 ×sin(A)-V L2 ×sin(A-120°)…(5) V L2 = (V L1 ×sin(A)-V dc ) / sin(A-120°)…(6)

[0042] In a similar manner, the inverter control unit 50a calculates the phase voltage V L3 Specifically, the inverter control unit 50a calculates the phase voltage V L2 Phase voltage V at the zero crossing point L1 The phase B of the phase voltage V is calculated. L1 and the phase voltage V L3Ask for.

[0043] V dc =V L3 ×sin(B-240°)-V L1 ×sin(B) …(7) V L3 = (V L1 ×sin(B)-V dc ) / sin(B-240°)…(8)

[0044] In this embodiment, the zero-cross detector 60 detects the zero-cross points of the phase voltage of one of the three-phase AC voltages, but the inverter control unit 50a may also have the function of detecting the zero-cross points. That is, a means (e.g., a voltage sensor) may be provided to detect the instantaneous value of the phase voltage of one of the three-phase AC voltages, and the inverter control unit 50a may detect the zero-cross points based on the detection result.

[0045] Next, the operation of the electric motor drive device 100a according to the present embodiment will be described. Fig. 8 is a flowchart showing an example of the operation of the electric motor drive device 100a according to the second embodiment. In Fig. 8, the same step numbers as in Fig. 2 indicate the same processes. The description of the processes with the same step numbers as in Fig. 2 will be omitted.

[0046] After the inverter control unit 50a acquires the DC voltage value in step S1, the zero-cross detection unit 60 detects the phase voltage V L1 Next, the inverter control unit 50a calculates the phase A from the zero cross points detected by the zero cross detection unit 60 (step S12).

[0047] Next, the inverter control unit 50a detects the DC voltage V dc The voltages of each phase of the three-phase AC are calculated based on the maximum value of the DC voltage V dc The maximum value of the DC voltage V dc The inverter control unit 50a calculates the voltages of the respective phases (V L1 , V L2 , V L3 ) is calculated.

[0048] Next, the inverter control unit 50a checks whether the difference between the phase voltages of the three-phase AC is greater than a predetermined unbalance detection threshold (step S14). Note that the unbalance detection threshold used in step S14 is different from the unbalance detection threshold used in step S3 shown in FIG. 2 and described in the first embodiment. In step S14, the inverter control unit 50a checks whether the difference between the phase voltages V L1 and V L2 The difference between the phase voltage V L2 and V L3 and the phase voltage V L3 and V L1 If one or more of the calculated differences are greater than the unbalance detection threshold, the inverter control unit 50a determines that the three-phase AC voltage is unbalanced (step S14: Yes) and suppresses the output of the inverter 20 (step S4). If all of the calculated differences are equal to or less than the unbalance detection threshold, the inverter control unit 50a determines that the three-phase AC voltage is not unbalanced (step S14: No) and continues normal operation of the inverter 20 (step S5).

[0049] As described above, the electric motor drive device 100a according to this embodiment includes a voltage detection unit 40 that detects the DC voltage between the three-phase diode bridge 10 and the DC reactor 30, a zero-cross detection unit 60 that monitors one phase of the three-phase AC voltage input from the power source 1 and detects zero-cross points of the voltage, and an inverter control unit 50a that calculates the phase voltages (effective values) of the three-phase AC voltage based on the DC voltage detected by the voltage detection unit 40 and the zero-cross points detected by the zero-cross detection unit 60 and detects an unbalanced state of the three-phase AC voltage based on the difference between the phase voltages. When the inverter control unit 50a detects an unbalanced state of the three-phase AC voltage, it suppresses the output of the inverter 20. This embodiment realizes an electric motor drive device 100a that can prevent malfunctions such as breaker tripping and damage to components mounted on a circuit board when an unbalance in the three-phase AC voltage occurs, and also enables the device to be made more compact. Furthermore, because the phase voltages of the three-phase AC voltage are calculated and whether or not an unbalanced state exists is determined based on the phase voltages, the unbalanced state can be detected with high accuracy.

[0050] Third Embodiment In a third embodiment, an application example of the electric motor drive devices 100 and 100a described in the first and second embodiments will be described.

[0051] Fig. 9 is a diagram showing a configuration example of an air conditioner 200 according to embodiment 3. The air conditioner 200 shown in Fig. 9 is realized by applying the electric motor drive device 100 described in embodiment 1. The air conditioner 200 is an example of a refrigeration cycle device realized by applying the electric motor drive device 100. Note that the electric motor drive device 100 may be replaced with the electric motor drive device 100a described in embodiment 2.

[0052] The air conditioner 200 includes an electric motor drive device 100 connected to a power source 1 that 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 refrigerant piping 76. The compressor 71 includes a motor 2 that is driven by the three-phase AC power supplied from the electric motor drive device 100, and a compression mechanism 77 that compresses the refrigerant. The motor 2 operates the compression mechanism 77.

[0053] A refrigeration cycle is formed by circulating a refrigerant through 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.

[0054] The air conditioner 200 is not limited to a separate type air conditioner in which the outdoor unit is separated from the indoor unit, but may also be an integrated type air conditioner in which the compressor 71, indoor heat exchanger 75, and outdoor heat exchanger 73 are provided within a single housing.

[0055] Although the air conditioner 200 has been described as an example of a refrigeration cycle device equipped with the electric motor drive device 100, the refrigeration cycle device is not limited to the air conditioner 200 and may also be a refrigerator, a heat pump water heater, etc.

[0056] In addition, in the present embodiment, a configuration example has been described in which the motor 2 is applied as the drive source for the compressor 71 and is driven by the electric motor drive device 100. However, the motor 2 driven by the electric motor drive device 100 may also be applied as the drive source for driving an indoor unit blower and an outdoor unit blower (not shown) that are provided in the air conditioner 200. Furthermore, the motor 2 driven by the electric motor drive device 100 may also be applied as the drive source for each of the indoor unit blower, the outdoor unit blower, and the compressor 71.

[0057] 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 in the power supply 1 without being affected by fluctuations in the load connected to the inverter 20. Furthermore, when a voltage imbalance is detected, the output of the inverter 20 is suppressed, thereby preventing problems such as breaker tripping and damage to components mounted on the circuit board. This makes it possible to maintain the reliability and product life of the air conditioner 200. 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, the same effects as those of the air conditioner 200 can be achieved.

[0058] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention.

[0059] 1 Power supply, 2 Motor, 3 Electrolytic capacitor, 10 Three-phase diode bridge, 20 Inverter, 30 DC reactor, 40 Voltage detection unit, 50, 50a Inverter control unit, 60 Zero-cross detection unit, 71 Compressor, 72 Four-way valve, 73 Outdoor heat exchanger, 74 Expansion valve, 75 Indoor heat exchanger, 76 Refrigerant piping, 77 Compression mechanism, 100, 100a Electric motor drive device, 200 Air conditioner.

Claims

1. A three-phase diode bridge that rectifies three-phase AC voltage and converts it into DC voltage; A smoothing capacitor that smoothes the DC voltage; a DC reactor provided between the three-phase diode bridge and the smoothing capacitor; an inverter that converts the DC voltage smoothed by the smoothing capacitor into an AC voltage and outputs the AC voltage to a motor; a voltage detection unit that detects a DC voltage output from the three-phase diode bridge; an inverter control unit 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 by the voltage detection unit, and controls the inverter based on a detection result of the unbalanced state; a zero-cross detection unit that detects a zero-cross point of any one of the three-phase AC voltages; Equipped with the inverter control unit detects an unbalanced state of the three-phase AC voltage based on the DC voltage value and the zero-cross point detected by the zero-cross detection unit. Electric motor drive unit.

2. When the inverter control unit detects an unbalanced state of the three-phase AC voltage, the inverter control unit suppresses the output of the inverter to be smaller than the output when the three-phase AC voltage is in a normal state.

2. The electric motor drive device according to claim 1.

3. the inverter control unit detects a peak of a ripple included in the DC voltage output by 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 the peaks of adjacent ripples is greater than a predetermined threshold value.

2. The electric motor drive device according to claim 1.

4. the inverter control unit detects, based on the DC voltage value, a peak of a ripple included in the DC voltage output by the three-phase diode bridge, 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 each phase to detect an unbalanced state of the three-phase AC voltage.

4. An electric motor drive device according to claim 1.

5. The electric motor drive device according to claim 1, The electric motor drive device generates drive power for a motor that operates a compression mechanism that compresses the refrigerant circulating in a refrigeration cycle. Air conditioner.