Power converter and refrigeration cycle system

Abstract

The power converter (100) includes an AC-DC converter (27) that converts the power supply voltage to a desired DC voltage, a DC-AC converter (29) that converts the DC voltage to a drive voltage, an additional circuit (30) that reduces common-mode current flowing through the power converter (100) and suppresses noise, a breaker (20) that detects overcurrent flowing from the AC power supply (50) to the power converter (100) and disconnects the electrical connection between the AC power supply (50) and the power converter (100), and an overcurrent suppression means (82) that suppresses overcurrent flowing through the additional circuit (30), wherein the current capacity of the breaker (20) is greater than the current capacity of the elements of the additional circuit (30).

Description

Technical Field

[0001] The present disclosure relates to a power conversion device and a refrigeration cycle device that convert a power supply voltage applied from an AC power supply into a drive voltage for a motor.

Background Art

[0002] A power conversion device used in an air conditioner, which is one of refrigeration cycle devices, includes an AC-DC conversion device that converts an AC voltage output from an AC power supply into a DC voltage, and a DC-AC conversion device that converts the DC voltage into an AC voltage. In this type of power conversion device, leakage current can be a problem. The leakage current is a high-frequency current that flows through the stray capacitance between the compressor, which is the load, and the ground potential by switching control for the switching elements included in the DC-AC conversion device. The leakage current flowing to the ground potential returns to the air conditioner, which is the source of generation, through a grounding point where the AC power supply is grounded, etc., and is thus also called "common mode current".

[0003] Patent Document 1 below discloses a configuration including an additional circuit including a leakage current detector, which is a detection unit for detecting a current corresponding to the common mode current, and a compensation current output unit that generates and outputs a compensation current for compensating the common mode current when the detected current is greater than a threshold value.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The compensating current output section is configured to inject compensating current into the ground potential, making it susceptible to the effects of lightning surges and other surges that cause fluctuations in the voltage to ground. A lightning surge is a transient high voltage generated by lightning. When a lightning surge occurs, a high-amplitude pulse voltage is superimposed on the common-mode voltage, causing a high-amplitude pulse current that would not normally occur to flow through the compensating current output section. This can lead to a short-circuit failure of the drive element provided in the compensating current output section. If the drive element short-circuits, an excessive current will flow through the additional circuit including the compensating current output section.

[0006] In power conversion devices, if a switching element on the main circuit side, such as an AC / DC converter or a DC / AC converter, short-circuits, the circuit breaker or protection circuit activates to interrupt the overcurrent before secondary damage occurs, such as damage to other elements besides the short-circuited switching element. On the other hand, in auxiliary circuits, which are not part of the main circuit, the current flowing during normal operation is small, around a few mA, so the elements used in the auxiliary circuits are selected to have a smaller current capacity than the elements on the main circuit side. For this reason, elements in the auxiliary circuits may experience overcurrent even at currents that would not cause the circuit breaker or protection circuit to activate. Consequently, auxiliary circuits face the challenge of a high risk of secondary damage, where other elements besides the faulty element are damaged by overcurrent that flows in the short time before the circuit breaker or protection circuit activates, or when the circuit breaker or protection circuit does activate.

[0007] This disclosure has been made in view of the above, and aims to provide a power conversion device that can reduce the risk of secondary damage in the additional circuit. [Means for solving the problem]

[0008] To solve the above-mentioned problems and achieve the objective, the power conversion device according to this disclosure is a power conversion device that converts a power supply voltage applied from an AC power source into a drive voltage for a motor, and comprises an AC-DC converter, a DC-AC converter, an additional circuit, a circuit breaker, and an overcurrent suppression means. The AC-DC converter converts the power supply voltage into a desired DC voltage, and the DC-AC converter converts the DC voltage into a drive voltage. The additional circuit reduces common-mode current flowing through the power conversion device to suppress noise. The overcurrent suppression means suppresses overcurrent flowing through the additional circuit. The circuit breaker detects overcurrent flowing from the AC power source to the power conversion device and disconnects the electrical connection between the AC power source and the power conversion device. The current capacity of the circuit breaker is greater than the current capacity of the elements of the additional circuit. [Effects of the Invention]

[0009] The power conversion device described herein has the effect of reducing the risk of secondary damage in the additional circuit. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows a first configuration example of a power conversion device according to Embodiment 1. [Figure 2] A diagram illustrating the essential aspects of the configuration and operation of the power converter according to Embodiment 1. [Figure 3] This figure shows a second configuration example of the power conversion device according to Embodiment 1. [Figure 4] A diagram showing an example configuration of a power conversion device according to Embodiment 2. [Figure 5] This figure shows an example configuration of a power conversion device according to Embodiment 3. [Figure 6] A diagram showing an example configuration of a refrigeration cycle device according to Embodiment 4. [Modes for carrying out the invention]

[0011] The power conversion device and refrigeration cycle device according to the embodiments of this disclosure will be described in detail below with reference to the attached drawings.

[0012] Embodiment 1. Figure 1 shows a first configuration example of the power converter 100 according to Embodiment 1. The power converter 100 according to Embodiment 1 drives the motor 61 by converting the power supply voltage applied from the AC power supply 50 into a drive voltage for the motor 61. When the power converter 100 is mounted on a refrigeration cycle system, examples of loads are a compressor or a fan. . electric Force conversion device 10 0 A circuit breaker, or breaker 20, is provided. The breaker 20 is a protective device that protects the power converter 100 from overcurrent. The breaker 20 detects the overcurrent flowing from the AC power source 50 to the power converter 100 and interrupts the electrical connection between the AC power source 50 and the power converter 100.

[0013] The midpoint 54 of the AC power supply 50 is grounded to the earth potential 51. The earth potential 51 is the potential of a grounding wire or grounding surface (not shown), and serves as the reference potential for the power supply voltage. In Figure 1, the AC power supply 50 is shown as a single-phase three-wire system, but it is not limited to this. The AC power supply 50 may be a single-phase two-wire system, a three-phase three-wire system, or a three-phase four-wire system. The power distribution method of the AC power supply 50 is determined according to the specifications of the refrigeration cycle equipment.

[0014] The power converter 100 is Breaker 20 and, The system comprises a noise filter 21, an AC-DC converter 27, a smoothing capacitor 28, a DC-AC converter 29, an additional circuit 30, and a control unit 80. Figure 1 shows an example in which the noise filter 21 is mounted on the first substrate 71, the AC-DC converter 27, the smoothing capacitor 28, and the DC-AC converter 29 are mounted on the second substrate 72, the additional circuit 30 is mounted on the third substrate 73, and the control unit 80 is mounted on the fourth substrate 74. Excluding breaker 20 These components, along with several other devices (not shown), including a motor 61, are housed within a housing 70. The housing 70 is grounded, thereby electrically connecting to an earth potential 52, which is the same potential as earth potential 51.

[0015] The noise filter 21 is a passive filter composed of passive elements. The noise filter 21 is disposed between the AC power supply 50 and the AC-DC converter 27. The noise filter 21 operates to reduce the noise current flowing in and out of the power conversion device 100.

[0016] The AC-DC converter 27 is a power converter that converts the power supply voltage applied from the AC power supply 50 into a desired DC voltage. The input side of the AC-DC converter 27 is connected to the power lines 11, 12 for electrically connecting the AC power supply 50 and the AC-DC converter 27, and the output side of the AC-DC converter 27 is connected to the power lines 13, 14 for electrically connecting the AC-DC converter 27 and the DC-AC converter 29. The AC-DC converter 27 converts the power supply voltage applied from the AC power supply 50 into a desired DC voltage and outputs it to the DC-AC converter 29.

[0017] The DC-AC converter 29 is a power converter that converts the DC voltage output from the AC-DC converter 27 into a drive voltage for the motor 61. Specifically, the DC-AC converter 29 includes a plurality of switching elements 16, converts the DC voltage output from the AC-DC converter 27 into a drive voltage for the motor 61, and drives the motor 61.

[0018] The smoothing capacitor 28 is disposed between the power line 13 and the power line 14, smooths and holds the DC voltage converted by the AC-DC converter 27. Thereby, a smoothed voltage is applied to the DC-AC converter 29.

[0019] The control unit 80 has a processor and a memory (not shown). A program read by the processor is stored in the memory. The processor reads the program from the memory and performs various arithmetic processes by executing the program. Based on the arithmetic processes of the processor, the control unit 80 generates a control signal for controlling the switching element 16 of the DC-AC conversion device 29 and outputs it to the DC-AC conversion device 29. When the AC-DC conversion device 27 has a switching element, the control unit 80 generates a control signal for controlling the switching element and outputs it to the AC-DC conversion device 27.

[0020] The addition circuit 30 includes a detection unit 22, a control power supply unit 24, a compensation signal generation unit 25, a compensation signal output unit 26, and an overcurrent suppression means 82. The addition circuit 30 is an active filter provided with active elements, which reduces the common-mode current flowing through the inside of the power conversion device 100 and suppresses the noise caused by the common-mode current.

[0021] The detection unit 22 is arranged at the subsequent stage of the noise filter 21 and detects a first physical quantity correlated with the common-mode current flowing through the inside of the power conversion device 100 via the ground potential 51. The detection unit 22 is configured to have a common-mode transformer 221 and uses the common-mode transformer 221 to detect the common-mode current flowing through the power lines 11, 12. The common-mode transformer 221 has windings, and FIG. 1 shows an example of detecting the voltage generated in the windings as a first physical quantity correlated with the common-mode current. That is, the detected voltage of the windings is an example of the first physical quantity correlated with the common-mode current. The detection unit 22 outputs the detected value of the common-mode current detected by the windings to the compensation signal generation unit 25.

[0022] The control power supply unit 24 generates and supplies power to operate the compensation signal generation unit 25. Figure 1 shows a configuration in which the control power supply unit 24 comprises a diode bridge in which four diodes are connected in a full bridge configuration and a capacitor connected in parallel to the diode bridge, but the system is not limited to this configuration. Also, Figure 1 shows an example in which AC power branched from power lines 11 and 12 is drawn into the control power supply unit 24, but the system is not limited to this example. DC power branched from power lines 13 and 14 may also be drawn into the control power supply unit 24.

[0023] The overcurrent suppression means 82 is positioned between the detection unit 22 and the control power supply unit 24. The purpose and significance of positioning the overcurrent suppression means 82 will be described later.

[0024] The compensation signal generation unit 25 includes gate resistors 231 and 232, and voltage-driven elements 251 and 252. An example of the voltage-driven elements 251 and 252 is the MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) shown in the figure. Alternatively, current-driven elements may be used instead of the voltage-driven elements 251 and 252. An example of a current-driven element is a bipolar transistor.

[0025] The compensation signal generation unit 25 generates a compensation current as a compensation signal to cancel out the common-mode current by driving voltage-driven elements 251 and 252 with a control voltage from the control power supply unit 24, based on the detected value detected by the detection unit 22. The compensation current is a current that is in opposite phase to the common-mode current. This compensation current is an example of a second physical quantity, another example of a second physical quantity is the compensation voltage. The compensation voltage is generated based on the detected value detected by the detection unit 22 and applied to the power lines 11 and 12 between the detection unit 22 and the AC / DC converter 27. The configuration in which the compensation signal generation unit 25 outputs a compensation voltage as a compensation signal is well known, and further explanation is omitted here.

[0026] In the compensation signal generation unit 25, the filter gain, which is one of the characteristics of the add-on circuit 30, is determined by the gate resistors 231 and 232. The gate resistors 231 and 232 adjust the detected value detected by the detection unit 22, and the voltage-driven elements 251 and 252 are driven by the adjusted detected value. In Figure 1, only the gate resistors 231 and 232 are shown as means for adjusting the filter gain of the add-on circuit 30, but this is not the only example. The filter gain of the add-on circuit 30 can also be determined by adjusting the detected value detected by the detection unit 22 using a configuration other than the gate resistors 231 and 232, or by adjusting the detected value detected by the detection unit 22 using a configuration other than the gate resistors 231 and 232. Furthermore, if the compensation signal generation unit 25 can drive the voltage-driven elements 251 and 252 using the detected value detected by the detection unit 22 as is, the gate resistors 231 and 232 may be omitted.

[0027] The compensation signal output unit 26 includes an injection resistor 261 and an injection capacitor 262. The compensation signal output unit 26 injects the compensation signal generated by the compensation signal generation unit 25 into the ground potential 52 via the injection resistor 261 and the injection capacitor 262. Note that the connection order of the injection resistor 261 and the injection capacitor 262 in the compensation signal output unit 26 may be the reverse of that shown in the figure. That is, the injection resistor 261 may be placed on the side of the ground potential 52. Also, the compensation signal output unit 26 only needs to have at least one injection capacitor 262, and the injection resistor 261 is optional.

[0028] As described above, the additional circuit 30 of the power converter 100 according to Embodiment 1 operates to reduce the common-mode current leaking from the power converter 100 to ground by injecting a compensation current to ground. Ideally, the compensation current injected to ground should match the current waveform obtained by inverting the amplitude of the common-mode current, but any waveform is acceptable as long as it reduces the common-mode current. Therefore, the compensation current injected to ground may have slightly different amplitudes and other characteristics from the current waveform obtained by inverting the amplitude of the common-mode current, and does not need to match perfectly.

[0029] Note that the configuration of the power converter 100 shown in Figure 1 is just one example, and the arrangement of the AC / DC converter 27, smoothing capacitor 28, control power supply unit 24, etc. may differ from that shown in Figure 1. Also, although Figure 1 describes the case where the power supplied to the power converter 100 is AC power supplied from an AC power source 50, the system is not limited to this example. Although not shown in the illustration, the system can also be applied to the case where the power supplied to the power converter 100 is DC power supplied from a DC power source.

[0030] Furthermore, Figure 1 illustrates the parasitic capacitance to ground 62 that may occur between the motor 61 and the ground potential 52 to which the housing 70 is electrically connected. This assumes that a common-mode current may flow from the motor 61 to ground via the parasitic capacitance to ground 62.

[0031] Next, the configuration and operation of the power converter 100 according to Embodiment 1 will be explained with reference to Figures 2 and 3. Figure 2 is a diagram used to explain the configuration and operation of the power converter 100 according to Embodiment 1. Figure 3 is a diagram showing a second configuration example of the power converter 100 according to Embodiment 1.

[0032] In the additional circuit 30 of the power converter 100 according to Embodiment 1, for example, if either of the voltage-driven elements 251 and 252 in the compensation signal generation unit 25 short-circuits, an overcurrent flows through the dashed path shown in Figure 2 at the timing when the other element that is not short-circuited is controlled to turn ON.

[0033] In the auxiliary circuit 30, the current flowing during normal operation is small, only a few mA. For this reason, the elements used in the auxiliary circuit 30 are selected to have smaller current capacities compared to the elements in the main circuit, such as the AC / DC converter 27, the smoothing capacitor 28, and the AC / DC converter 29. Consequently, the significance of overcurrent in the auxiliary circuit 30 and overcurrent in the main circuit differs significantly in terms of the magnitude of the current.

[0034] Due to the circumstances described above, the power converter 100 according to Embodiment 1 has the characteristic that the current capacity of the breaker 20 is greater than the current capacity of each element on the auxiliary circuit 30 side. Therefore, if an overcurrent flows that would damage the elements on the main circuit side, the breaker 20 will operate, and the electrical connection between the AC power supply 50 and the power converter 100 will be interrupted. On the other hand, even if there is an overcurrent that would damage the elements on the auxiliary circuit 30 side, if that overcurrent is not a current that would damage the elements on the main circuit side, the breaker 20 will not operate, thus increasing the risk of secondary damage, such as damage to elements other than the faulty element.

[0035] Therefore, the power converter 100 according to Embodiment 1 has an overcurrent suppression means 82 placed between the detection unit 22 and the control power supply unit 24. The overcurrent suppression means 82 is provided on the compensation signal path through which the compensation signal flows. The overcurrent suppression means 82 operates to suppress the overcurrent when an overcurrent flows through the additional circuit 30.

[0036] In the first configuration example shown in Figures 1 and 2, the overcurrent suppression means 82 is placed between the detection unit 22 and the control power supply unit 24. However, as in the second configuration example shown in Figure 3, the overcurrent suppression means 82 may also be placed between the compensation signal generation unit 25 and the compensation signal output unit 26, taking into account the current flowing to ground. Note that these first and second configuration examples are just examples, and the overcurrent suppression means 82 may be placed at any position along the compensation signal path through which the compensation signal flows.

[0037] An example of the overcurrent suppression means 82 is an element or component such as a fuse or a PTC (Positive Temperature Coefficient) thermistor. A fuse is an example of a component that switches between conducting and interrupting the compensation signal path. The overcurrent suppression means 82 may also be a means that switches from low impedance to high impedance. A PTC thermistor is an example of an element that switches from low impedance to high impedance. The overcurrent suppression means 82 may also be, for example, a relay. A relay is an example of a device that switches between conducting and interrupting the compensation signal path.

[0038] As described above, the power converter according to Embodiment 1 is a power converter that converts a power supply voltage applied from an AC power source into a drive voltage for a motor, and comprises the following AC-DC converter, DC-AC converter, additional circuit, circuit breaker, and overcurrent suppression means. The AC-DC converter converts the power supply voltage into a desired DC voltage, and the DC-AC converter converts the DC voltage into a drive voltage. The additional circuit reduces common-mode current flowing through the power converter to suppress noise. The overcurrent suppression means suppresses overcurrent flowing through the additional circuit. The circuit breaker detects overcurrent flowing from the AC power source to the power converter and disconnects the electrical connection between the AC power source and the power converter. The current capacity of the circuit breaker is greater than the current capacity of the elements of the additional circuit. In a power converter equipped with an AC-DC converter and a DC-AC converter, even if an overcurrent flows through the additional circuit, the circuit breaker may not operate because its current capacity is greater than the current capacity of the elements of the additional circuit. In the power converter according to Embodiment 1, the overcurrent suppression means operates to suppress the overcurrent flowing through the additional circuit, so that even if the circuit breaker does not operate, the overcurrent flowing through the additional circuit can be suppressed. Therefore, by using the power converter according to Embodiment 1, the risk of secondary damage in the additional circuit can be reduced.

[0039] Furthermore, in the power converter according to Embodiment 1, the additional circuit includes a detection unit, a compensation signal generation unit, and a compensation signal output unit, as shown below. The detection unit detects a first physical quantity correlated with the common-mode current. The compensation signal generation unit generates a compensation signal, which is a second physical quantity for canceling out the common-mode current, such as a compensation current or compensation voltage, based on the first physical quantity detected by the detection unit. The compensation signal output unit injects or applies the compensation signal to the ground potential that serves as the reference for the power supply voltage or to a designated location inside the power converter. Overcurrent suppression means are provided in the compensation signal path through which the compensation signal flows. The overcurrent suppression means may be an element or component that switches between conducting and interrupting the compensation signal path, or an element or device that switches from low impedance to high impedance. Using such overcurrent suppression means makes it possible to construct the power converter according to Embodiment 1 at low cost.

[0040] Embodiment 2. Figure 4 shows an example configuration of the power converter 100A according to Embodiment 2. The power converter 100A according to Embodiment 2 includes a notification unit 84 that generates notification information confirmed by the control unit 80, and a display unit 86 that displays the notification information confirmed by the control unit 80. The notification information confirmed by the control unit 80 is information that the current flowing through the additional circuit 30 is suppressed by the operation of the overcurrent suppression means 82. The control unit 80 can determine that the overcurrent suppression means 82 has operated by the change in the current flowing through the additional circuit 30. The change in the current flowing through the additional circuit 30 can be determined, for example, by a current sensor (not shown) that measures the current flowing through the additional circuit 30. Note that the configuration shown in Figure 4 is an example when the notification unit 84 and the display unit 86 are applied to the second configuration example shown in Figure 3, but they may also be applied to the first configuration example shown in Figure 1.

[0041] If the power converter 100A is an air conditioning system, an example of the display unit 86 is a display panel installed on the outdoor unit or indoor unit, or a light-emitting means such as an LED (Light Emitting Diode). By providing the display unit 86, the user and the service engineer performing maintenance can be notified that the overcurrent suppression means 82 is operating. If the overcurrent suppression means 82 is an irreversible component such as a fuse, it will be necessary to replace this irreversible component. By having the notification unit 84 and the display unit 86, it is possible to quickly communicate information prompting replacement to the user and the service engineer.

[0042] The display unit 86 does not necessarily have to be a display panel or LED provided by the air conditioning system; it may be an external display means. If the notification unit 84 has a communication function, the display unit 86 may be the display unit of a communication device such as a remote controller, mobile terminal, or information and communication terminal that can communicate with the notification unit 84. Alternatively, notification information may be transmitted to a server device that can communicate with the notification unit 84, and the mobile terminal or information and communication terminal may access the server device and display the notification information.

[0043] As described above, the power converter according to Embodiment 2 includes a notification unit for notifying that the current flowing to the additional circuit is being suppressed by the operation of the overcurrent suppression means. With the power converter according to Embodiment 2, it is possible to recognize that the overcurrent suppression means has been activated, and if the overcurrent suppression means is an irreversible component, information prompting the replacement of the irreversible component can be promptly communicated to the user and service engineer. Therefore, with the power converter according to Embodiment 2, it is possible to enjoy the effects of Embodiment 1 while enabling service engineers to provide appropriate maintenance services.

[0044] Embodiment 3. Figure 5 shows an example configuration of the power converter 100B according to Embodiment 3. In the power converter 100 according to Embodiment 1, the detection unit 22, control power supply unit 24, compensation signal generation unit 25, compensation signal output unit 26, and overcurrent suppression means 82 were mounted on the third substrate 73. In contrast, in the power converter 100B according to Embodiment 3, the overcurrent suppression means 82 is mounted on a fifth substrate 75, which is different from the third substrate 73. That is, in Embodiment 3, the overcurrent suppression means 82 is mounted on a substrate different from the second substrate 72 on which the elements constituting the main circuit are mounted, and is also mounted on a fifth substrate 75, which is different from the third substrate 73 on which the elements constituting the additional circuit 30 are mounted. Note that the configuration shown in Figure 5 is an example of applying the configuration on which the substrate on which the overcurrent suppression means 82 is mounted is a separate substrate to the first configuration example shown in Figure 1, but it may also be applied to the second configuration example shown in Figure 3, or the configuration example shown in Figure 4.

[0045] As explained in Embodiment 2, if the overcurrent suppression means 82 is an irreversible component such as a fuse, it becomes necessary to replace this irreversible component. In the case of the power converter 100B according to Embodiment 3, not only is it possible to replace the irreversible component itself, but it is also possible to replace the entire circuit board. Furthermore, even if the overcurrent suppression means 82 is not an irreversible component, it may become necessary to replace the overcurrent suppression means 82 due to deterioration in its performance or failure. In such cases, the power converter 100B according to Embodiment 3 makes it possible to replace the entire circuit board, thus reducing the time required for replacement work.

[0046] As described above, in the power conversion device according to Embodiment 3, the substrate on which the overcurrent suppression means is mounted is a different substrate from the substrate on which the AC-DC converter and the DC-AC converter are mounted, and is also a different substrate from the substrate on which each element constituting the additional circuit is mounted. Therefore, with the power conversion device according to Embodiment 3, when replacing the overcurrent suppression means, it is possible to replace each substrate, which reduces the time required for replacement work and improves the maintainability of the device.

[0047] Embodiment 4. Figure 6 shows an example configuration of the refrigeration cycle device 900 according to Embodiment 4. The refrigeration cycle device 900 according to Embodiment 4 includes the power converter 100 described in Embodiment 1. The refrigeration cycle device 900 according to Embodiment 4 can be applied to products equipped with a refrigeration cycle, such as air conditioners, refrigerators, freezers, and heat pump water heaters. In Figure 6, elements having the same functions as in Embodiment 1 are denoted by the same reference numerals as in Embodiment 1.

[0048] The refrigeration cycle device 900 includes a compressor 315 with a built-in motor 61 in Embodiment 1, a four-way valve 902, an indoor heat exchanger 906, an expansion valve 908, and an outdoor heat exchanger 910, all of which are connected via refrigerant piping 912.

[0049] Inside the compressor 315 are a compression mechanism 904 for compressing the refrigerant and a motor 61 for operating the compression mechanism 904.

[0050] The refrigeration cycle unit 900 can operate in heating or cooling mode by switching the four-way valve 902. The compression mechanism 904 is driven by a motor 61 that is controlled by variable speed control.

[0051] During heating operation, as indicated by the solid arrows, the refrigerant is pressurized by the compression mechanism 904 and sent out, then returns to the compression mechanism 904 after passing through the four-way valve 902, indoor heat exchanger 906, expansion valve 908, outdoor heat exchanger 910 and the four-way valve 902.

[0052] During cooling operation, as indicated by the dashed arrows, the refrigerant is pressurized by the compression mechanism 904 and sent out, then returns to the compression mechanism 904 after passing through the four-way valve 902, the outdoor heat exchanger 910, the expansion valve 908, the indoor heat exchanger 906 and the four-way valve 902.

[0053] During heating operation, the indoor heat exchanger 906 acts as a condenser to release heat, and the outdoor heat exchanger 910 acts as an evaporator to absorb heat. During cooling operation, the outdoor heat exchanger 910 acts as a condenser to release heat, and the indoor heat exchanger 906 acts as an evaporator to absorb heat. The expansion valve 908 reduces the pressure of the refrigerant and causes it to expand.

[0054] Although the refrigeration cycle device 900 according to Embodiment 4 was described as being equipped with the power converter 100 described in Embodiment 1, it is not limited to this. It may be equipped with either the power converter 100A of Embodiment 2 or the power converter 100B of Embodiment 3.

[0055] The configurations shown in the above embodiments are merely examples, and it is possible to combine them with other known technologies, combine different embodiments, and omit or modify parts of the configuration without departing from the gist of the invention. [Explanation of Symbols]

[0056] 11,12,13,14 Power lines, 16 Switching elements, 20 Circuit breakers, 21 Noise filters, 22 Detection units, 24 Control power supply units, 25 Compensation signal generation units, 26 Compensation signal output units, 27 AC / DC converters, 28 Smoothing capacitors, 29 AC / DC converters, 30 Additional circuits, 50 AC power supplies, 51,52 Ground potential, 54 Midpoint, 61 Motor, 62 Parasitic capacitance to ground, 70 Housing, 71 First circuit board, 72 Second circuit board, 73 Third circuit board, 74 Fourth circuit board, 75 Fifth circuit board, 80 Control unit, 82 Overcurrent suppression means, 84 Notification unit, 86 Display unit, 100,100A,100B Power converters, 221 Common mode transformers, 231,232 Gate resistors, 251,252 Voltage-driven element, 261 injection resistor, 262 injection condenser, 315 compressor, 900 refrigeration cycle device, 902 four-way valve, 904 compression mechanism, 906 indoor heat exchanger, 908 expansion valve, 910 outdoor heat exchanger, 912 refrigerant piping.

Claims

1. A power conversion device that converts the power supply voltage applied from an AC power source into a drive voltage for a motor, An AC-DC converter that converts the aforementioned power supply voltage to a desired DC voltage, A DC-to-AC converter that converts the DC voltage to the drive voltage, An additional circuit that reduces common-mode current flowing through the inside of the power converter to suppress noise, A circuit breaker that detects an overcurrent flowing from the AC power source to the power converter and interrupts the electrical connection between the AC power source and the power converter, An overcurrent suppression means for suppressing the overcurrent flowing through the aforementioned additional circuit, Equipped with, A power conversion device in which the current capacity of the circuit breaker is greater than the current capacity of the elements of the additional circuit.

2. The aforementioned additional circuit is A detection unit for detecting a first physical quantity correlated with the common-mode current, A compensation signal generation unit generates a compensation signal, which is a compensation current or compensation voltage, that is a second physical quantity for canceling out the common-mode current, based on the first physical quantity detected by the detection unit. The device includes a compensation signal output unit that injects or applies the compensation signal to the ground potential that serves as the reference for the power supply voltage or to a designated location inside the power converter, The overcurrent suppression means is provided in the compensation signal path through which the compensation signal flows. The power conversion device according to claim 1.

3. The overcurrent suppression means is an element or component that switches between conducting and interrupting the compensation signal path, or an element or device that switches from low impedance to high impedance. The power conversion device according to claim 2.

4. The system includes a notification unit for notifying that the current flowing through the additional circuit is being suppressed by the operation of the overcurrent suppression means. The power conversion device according to claim 1.

5. The substrate on which the overcurrent suppression means is mounted is a different substrate from the AC-DC converter and the substrate on which the AC-DC converter is mounted, and is also a different substrate from the substrate on which each element constituting the additional circuit is mounted. The power conversion device according to claim 1.

6. A refrigeration cycle apparatus comprising a power conversion device according to any one of claims 1 to 5.

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