Electric motor control device and refrigeration cycle device

Abstract

To provide a motor control device and a refrigeration cycle device capable of more finely coping with overcurrent while suppressing the number of comparators to be used.SOLUTION: The motor control device includes a current sensor that detects a current flowing through the motor, a temperature sensor that detects a temperature in the motor, a control device that determines an overcurrent protection threshold value for stopping the motor based on the temperature detected by the temperature sensor, a comparison unit that outputs an interruption signal based on a comparison between the current and the overcurrent protection threshold value, and a protection circuit that stops the motor when the interruption signal is sent.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology disclosed herein relates to an electric motor control device and a refrigeration cycle device, and in particular to protection of an electric motor against an overcurrent. [Background technology]

[0002] For example, permanent magnet motors with permanent magnets in the rotor are often used as motors for compressors in refrigeration cycle devices. In permanent magnet motors, a phenomenon called demagnetization occurs, in which the magnetic flux of the permanent magnet decreases as the temperature changes due to current flow through the windings. Furthermore, when the current or other allowable conditions are exceeded, a phenomenon called irreversible demagnetization occurs, in which the magnetic flux does not return to its pre-demagnetization state. To protect the motor, it is necessary to control the operation of a permanent magnet motor so that irreversible demagnetization of the permanent magnet does not occur.

[0003] To prevent irreversible demagnetization, the current supplied to the motor is prevented from becoming an overcurrent. For this reason, a motor control device that controls the power supply to a permanent magnet motor cuts off the power supply to the motor and stops it when the current supplied to the motor becomes an overcurrent (see, for example, Patent Document 1). At this time, an overcurrent protection threshold is set based on the value of the demagnetization current that causes irreversible demagnetization, and this is used as a criterion for whether the current supplied to the motor is an overcurrent. Here, because the value of the demagnetization current changes depending on the magnet temperature of the permanent magnet, multiple overcurrent protection thresholds are set corresponding to the magnet temperature. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-070531 Summary of the Invention [Problem to be solved by the invention]

[0005] In a motor control device, when comparing multiple overcurrent protection thresholds, it is common to configure multiple comparators in multiple stages. Therefore, if the overcurrent protection thresholds are set more precisely and the number of comparators is increased to perform a comparison more closely aligned with the demagnetizing current, the number of comparator stages increases, resulting in an increase in the board size. Furthermore, the increased number of comparators occupies output ports in the control device, such as a microcomputer, reducing the number of functions that can be assigned to the control device.

[0006] Therefore, in order to solve the above-mentioned problems, this disclosure aims to provide a motor control device and a refrigeration cycle device that can prevent the expansion of the board due to the comparator and can respond precisely to overcurrent protection. [Means for solving the problem]

[0007] The motor control device according to this disclosure includes a current sensor that detects the current flowing through the motor, a temperature sensor that detects the temperature in the motor, a control device that determines an overcurrent protection threshold that stops the motor based on the temperature detected by the temperature sensor, a comparison unit that outputs a shut-off signal based on a comparison between the current and the overcurrent protection threshold, and a protection circuit that stops the motor when the shut-off signal is sent.

[0008] A refrigeration cycle device according to the present disclosure includes the above-described motor control device. [Effects of the Invention]

[0009] According to this disclosure, it is possible to provide detailed measures for overcurrent protection without increasing the size of the device board. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram showing an example of an electric motor drive system centered around an electric motor control device 100 according to a first embodiment. [Figure 2] FIG. 4 is a diagram showing an example of the relationship between phase current and magnet temperature according to the first embodiment. [Figure 3] 3 is a diagram showing a flow of demagnetization protection control of the electric motor control device 100 according to the first embodiment. FIG. [Figure 4] FIG. 10 is a diagram showing an example of an electric motor drive system centered around an electric motor control device 100 according to a second embodiment. [Figure 5] FIG. 10 is a diagram showing an example of the relationship between phase current and magnet temperature according to the second embodiment. [Figure 6] FIG. 10 is a diagram showing a flow of demagnetization protection control of the electric motor control device 100 according to the second embodiment. [Figure 7] FIG. 10 is a diagram showing the configuration of an air conditioner 1 according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, motor control devices and refrigeration cycle devices according to embodiments will be described with reference to the drawings. In the following drawings, components with the same reference numerals are identical or equivalent and will be common throughout the following embodiments. The configurations of the components shown throughout the specification are merely examples and are not limited to the configurations described in the specification. In particular, the combinations of components are not limited to the combinations in each embodiment, and components described in other embodiments can be applied to other embodiments. Furthermore, the levels of pressure and temperature are not determined in relation to absolute values, but are determined relatively in terms of the state, operation, etc. of the device. In the drawings, the size relationships between components, such as devices and elements, may differ from the actual sizes.

[0012] Embodiment 1 1 is a diagram showing an example of an electric motor drive system centered around an electric motor control device 100 according to Embodiment 1. The electric motor drive system according to Embodiment 1 includes the electric motor control device 100 and an electric motor 300.

[0013] The motor control device 100 is a device that controls the power supply to the electric motor 300 to be supplied with power and performs drive control. Here, the electric motor 300 in the first embodiment is assumed to be a three-phase PM (Permanent Magnet) motor. A PM motor has low torque when driven. Furthermore, a PM motor is an energy-saving and highly efficient motor because no secondary current flows through the rotor. However, a PM motor has a permanent magnet in the rotor. A magnetic material such as a permanent magnet demagnetizes as the temperature rises. Furthermore, it is demagnetized when the temperature exceeds the Curie temperature. When a PM motor is used, the electric motor control device 100 controls the current so that it does not exceed an overcurrent, which is an excessive current flow due to demagnetization, and stops driving the electric motor 300 when the phase current exceeds the overcurrent.

[0014] The motor control device 100 in the first embodiment has a rectifier circuit 110, an inverter circuit 120, a comparison unit 130, a buffer circuit 140, and a drive control device 150. The rectifier circuit 110 and the inverter circuit 120 form a power conversion circuit.

[0015] The rectifier circuit 110 and the inverter circuit 120 constitute a power conversion device. The rectifier circuit 110 converts AC power from the three-phase AC power supply 200 into DC power. The inverter circuit 120 performs DC / AC conversion on the DC voltage converted by the rectifier circuit 110 to AC voltage of a desired drive frequency, and supplies the AC power to the electric motor 300. The drive frequency is determined by a drive control device 150, which will be described later.

[0016] The rectifier circuit 110 includes, for example, a rectifier 111, a reactor 112, and a smoothing capacitor 113. The rectifier 111 converts AC power from the three-phase AC power supply 200 into DC power. The rectifier 111 is, for example, a three-phase rectifier. The three-phase rectifier uses six rectification backflow prevention elements, such as diodes, connected in a bridge configuration. However, the present invention is not limited to this. The rectifier 111 may also be, for example, a PWM (Pulse Width Modulation) converter having semiconductor switching elements. The reactor 112 reduces harmonic components of the current flowing through the three-phase AC power supply 200. Here, the reactor 112 is intended to smooth the power supply current, and therefore may be provided between the three-phase AC power supply 200 and the rectifier 111. The smoothing capacitor 113 smooths the power converted by the rectifier 111.

[0017] As described above, the inverter circuit 120 is a device that converts DC voltage into AC voltage to control the power supply to the electric motor 300 and control the rotation speed of the electric motor 300. The inverter circuit 120 includes a power module. A power module is a package in which elements that perform power conversion and the like are housed in a housing. When the inverter circuit 120 is a three-phase output inverter, the power module houses six arms, each of which is configured by connecting in parallel switching elements 121, which are power semiconductor elements such as IGBTs, and diodes 122. The inverter circuit 120 of the first embodiment has three pairs of arms, each pair consisting of two arms. The multiple switching elements 121 included in each arm are controlled by the drive control device 150 to perform switching operations of turning on or off at predetermined timing.

[0018] The current detection unit 160 in the first embodiment detects a phase current supplied to the electric motor 300. The current detection unit 160 has a phase current sensor 161. The phase current sensor 161 detects the phase current and sends a phase current signal related to the detection to the comparison unit 130 and the drive control device 150. The phase current sensor 161 is, for example, a current transformer.

[0019] Furthermore, magnet temperature sensor 171 is a temperature sensor that detects the magnet temperature of the permanent magnet of electric motor 300 and sends a magnet temperature signal related to the detection to drive control device 150. Here, magnet temperature sensor 171 may be a sensor that detects a temperature that can estimate the temperature of the permanent magnet of electric motor 300, such as the temperature of a shell that serves as a container for the compressor, when electric motor 300 is mounted inside a compressor.

[0020] The comparison unit 130 has a current comparator 131, and outputs a tripping signal by comparing a voltage based on an overcurrent protection threshold signal sent from the drive control device 150 (described later) with a voltage based on a phase current signal including a current value detected by a phase current sensor 161 of the current detection unit 160. The tripping signal is, for example, a signal whose logic is inverted depending on whether the current detection value of the current detected by the phase current sensor 161 is larger or smaller than the overcurrent protection threshold. The current comparator 131 is, for example, a comparator. The comparator compares the voltage that is the overcurrent protection threshold with the voltage related to the current detected by the phase current sensor 161.

[0021] The buffer circuit 140 is a device that sends a gate drive signal from the drive control device 150 (described later) to the inverter circuit 120. The buffer circuit 140 also functions as a protection circuit that cuts off the gate drive signal from the drive control device 150 based on a cutoff signal from the comparison unit 130.

[0022] The drive control device 150 is a device that controls the entire motor control device 100. The drive control device 150 in the first embodiment has an inverter control unit 151, an overcurrent protection threshold setting unit 152, a threshold storage unit 153, and a D / A port unit 154. The inverter control unit 151 outputs a PWM (Pulse Width Modulation) gate drive signal and performs PWM control on the arms of the power module of the inverter circuit 120. The switching elements 121 of each arm housed in the power module of the inverter circuit 120 perform switching operations based on control signals from the drive control device 150, and convert a DC voltage into an AC voltage of an arbitrary drive frequency.

[0023] The threshold storage unit 153 associates the magnet temperature of the permanent magnet of the electric motor 300 with the overcurrent protection threshold, and stores the association data, for example, in the form of a table. The relationship between the magnet temperature and the overcurrent protection threshold will be described later. The overcurrent protection threshold setting unit 152 searches and references the threshold storage unit 153 based on the magnet temperature detected by the magnet temperature sensor 171, and sets the overcurrent protection threshold. The relationship between the magnet temperature and the overcurrent protection threshold will be described later. The drive control device 150 in the first embodiment also has a D / A port unit 154. The D / A port unit 154 converts the overcurrent protection threshold set by the overcurrent protection threshold setting unit 152 into an analog signal represented by a voltage, and transmits the converted signal to the comparison unit 130 as an overcurrent protection threshold signal.

[0024] The drive control device 150 is configured, for example, as hardware, with a microcomputer having a control arithmetic processing device such as a CPU (Central Processing Unit). The microcomputer has, for example, storage devices such as a ROM (Read Only Memory) and a RAM (Random Access Memory).

[0025] FIG. 2 is a diagram illustrating an example of the relationship between phase current and magnet temperature according to the first embodiment. For example, rare-earth permanent magnets used in PM motors demagnetize as the magnet temperature increases. Therefore, as the magnet temperature increases, current flows more easily, causing overcurrent. Driving the electric motor 300 affects the magnet temperature. To protect the electric motor 300 from overcurrent, an overcurrent protection threshold for the magnet temperature is determined based on the demagnetization current, which is the boundary between whether the current flowing through the electric motor 300 is an overcurrent. The permanent magnet according to the first embodiment has a large demagnetization current when the temperatures of the electric motor 300 and the permanent magnet are low, widening the range in which current can be supplied. This widens the driving range of the electric motor 300. Here, when determining the overcurrent protection threshold based on the demagnetization current, a margin may be added to account for noise, etc.

[0026] The threshold storage unit 153 of the drive control device 150 stores data showing the relationship between the magnet temperature and the overcurrent protection threshold, as shown in Fig. 2, for example, as data in a table format. The overcurrent protection threshold setting unit 152 of the drive control device 150 searches and references the data stored in the threshold storage unit 153 based on the magnet temperature detected by the magnet temperature sensor 171, and sets the overcurrent protection threshold.

[0027] 3 is a diagram showing a flow of demagnetization protection control of the motor control device 100 according to the first embodiment. The demagnetization protection control is mainly performed by the overcurrent protection threshold setting unit 152 of the drive control device 150. The overcurrent protection threshold setting unit 152 sets an overcurrent protection threshold based on the magnet temperature included in the magnet temperature signal sent from the magnet temperature sensor 171 (step S1). The D / A port unit 154 also adjusts the voltage based on the overcurrent protection threshold set by the overcurrent protection threshold setting unit 152, converts the overcurrent protection threshold into an analog signal, and sends the overcurrent protection threshold signal to the comparison unit 130 (step S2). For example, the D / A port unit 154 gradually changes the voltage within a range of 0 to 5 V according to the overcurrent protection threshold to generate the overcurrent protection threshold signal.

[0028] Meanwhile, the phase current sensor 161 of the current detection unit 160 detects the phase current related to the control (step S3) and sends a phase current signal to the comparison unit 130 and the drive control device 150 (step S4). When the phase current is smaller than the overcurrent protection threshold (YES in step S5), the current comparator 131 of the comparison unit 130 does not output a trip signal. Therefore, the inverter circuit 120 continues power conversion.

[0029] On the other hand, when the phase current is equal to or greater than the overcurrent protection threshold, a cutoff signal is output (step S6). Then, the buffer circuit 140 cuts off the gate drive signal from the drive control device 150 (step S7). As a result, the inverter circuit 120 stops power conversion.

[0030] As described above, in the electric motor control device 100 according to the first embodiment, the overcurrent protection threshold setting unit 152 of the drive control device 150 sets an overcurrent protection threshold by referring to the data stored in the threshold storage unit 153 based on the magnet temperature detected by the magnet temperature sensor 171. The current comparator 131 of the comparison unit 130 then compares the overcurrent protection threshold signal corresponding to the set overcurrent protection threshold with the phase current detected by the phase current sensor 161 to determine whether to output a tripping signal. This allows the overcurrent protection threshold to be precisely set without requiring a multi-stage comparator configuration or reducing the function allocation of the control device, and allows the current supplied to the electric motor 300 to be compared with the set overcurrent protection threshold. This allows for more precise overcurrent protection without increasing the circuit board size of the electric motor control device 100. Furthermore, because the overcurrent protection threshold can be precisely set in accordance with the demagnetizing current, the range of currents that do not become overcurrents can be expanded while still protecting the electric motor 300, thereby widening the driving range. This allows for highly reliable driving. Furthermore, when an overcurrent occurs, power supply can be stopped more quickly by cutting off the power supply using hardware such as current comparator 131 than by cutting off the power supply using software that uses a gate drive signal based on the result of calculation of the phase current by drive control device 150. Therefore, in motor control device 100 according to embodiment 1, it is possible to further protect motor 300.

[0031] Embodiment 2 Fig. 4 is a diagram showing an example of an electric motor drive system centered around an electric motor control device 100 according to embodiment 2. In Fig. 4, components that are given the same reference numerals as in Fig. 1 perform the same operations as those described in embodiment 1.

[0032] 4, current detection unit 160 in the second embodiment has U-phase current sensor 162 and W-phase current sensor 163. U-phase current sensor 162 detects the U-phase current and sends a U-phase current signal related to the detection to comparison unit 130, drive control device 150, and V-phase current detection circuit 180, which will be described later. W-phase current sensor 163 detects the W-phase current and sends a W-phase current signal related to the detection to comparison unit 130, drive control device 150, and V-phase current detection circuit 180, which will be described later.

[0033] The motor control device 100 of the second embodiment also has a V-phase current detection circuit 180. The V-phase current detection circuit 180 detects the V-phase current based on the U-phase current in the U-phase current signal and the W-phase current in the W-phase current signal, and sends the detected U-phase current signal to the comparison unit 130 and the drive control device 150.

[0034] Comparator 130 in the second embodiment has U-phase + side comparator 132, U-phase - side comparator 133, W-phase + side comparator 134, W-phase - side comparator 135, V-phase + side comparator 136, and V-phase - side comparator 137.

[0035] U-phase +-side comparator 132 outputs a tripping signal by comparing the voltage on the positive side based on the U-phase current signal including the U-phase current value with the voltage based on the +-side overcurrent protection threshold signal sent from drive control device 150. Here, U-phase +-side comparator 132 includes a half-wave rectifier (not shown) that extracts the positive portion of the U-phase current from the U-phase current signal before making the comparison. Similarly to U-phase +-side comparator 132, W-phase +-side comparator 134 and V-phase +-side comparator 136 also output tripping signals by comparing the voltage on the positive side based on the phase current signal of their respective phase with the voltage based on the +-side overcurrent protection threshold signal sent from drive control device 150.

[0036] Furthermore, U-phase -side comparator 133 outputs a tripping signal by comparing the voltage on the negative side determined by the U-phase current signal including the U-phase current value with the voltage determined by the -side overcurrent protection threshold signal sent from drive control device 150. Here, U-phase -side comparator 133 has a branching filter (not shown) that extracts the negative portion of the U-phase current from the U-phase current signal before making the comparison. Similarly to U-phase -side comparator 133, W-phase -side comparator 135 and V-phase -side comparator 137 also output tripping signals by comparing the voltage on the negative side determined by the phase current signal of their respective phase with the voltage determined by the -side overcurrent protection threshold signal sent from drive control device 150.

[0037] FIG. 5 is a diagram showing an example of the relationship between phase current and magnet temperature according to the second embodiment. FIG. 2, which was described in the first embodiment, focuses on the positive side of the phase current. FIG. 5 also defines an overcurrent protection threshold for the demagnetizing current on the negative side of the phase current. For example, if the current flowing through the electric motor 300 is unbalanced, such as when a bias is applied, and only one of the positive and negative phase currents is compared, the overcurrent protection threshold may not be exceeded even if the amplitude of the phase current is large. Therefore, the electric motor control device 100 according to the second embodiment defines a positive overcurrent protection threshold and a negative overcurrent protection threshold, which are the upper and lower limits of whether the current flowing through the electric motor 300 is an overcurrent.

[0038] The drive control device 150 stores data showing the relationship between the magnet temperature and the overcurrent protection threshold shown in Fig. 5 in a storage device (not shown), for example as table data. The overcurrent protection threshold setting unit 152 of the drive control device 150 references the table data based on the magnet temperature detected by the magnet temperature sensor 171, and sets a +-side overcurrent protection threshold that serves as the upper limit value of the normal phase current and a --side overcurrent protection threshold that serves as the lower limit value.

[0039] 6 is a diagram showing a flow of demagnetization protection control of the motor control device 100 according to the second embodiment. The demagnetization protection control is mainly performed by the overcurrent protection threshold setting unit 152 of the drive control device 150. The overcurrent protection threshold setting unit 152 sets a positive side overcurrent protection threshold and a negative side overcurrent protection threshold based on the magnet temperature included in the magnet temperature signal sent from the magnet temperature sensor 171 (step S11). The overcurrent protection threshold setting unit 152 also sends each overcurrent protection threshold signal, the voltage of which has been adjusted based on the set overcurrent protection threshold, to the comparison unit 130 (step S12).

[0040] Meanwhile, U-phase current sensor 162 and W-phase current sensor 163 of current detection unit 160 detect the U-phase current and W-phase current, respectively (step S13), and send the phase current signals to comparison unit 130 and V-phase current detection circuit 180 (step S14). V-phase current detection circuit 180 detects the V-phase current based on the U-phase current and W-phase current, and sends the V-phase current signal to comparison unit 130 (step S15).

[0041] U-phase + side comparator 132, U-phase - side comparator 133, W-phase + side comparator 134, W-phase - side comparator 135, V-phase + side comparator 136, and V-phase - side comparator 137 of comparison unit 130 compare the voltages associated with the corresponding phase current signals with the voltages associated with the overcurrent protection threshold signals. As a result, when the relationship "-side overcurrent protection threshold < phase current < +side overcurrent protection threshold" is satisfied for all phase currents (YES in step S16), comparison unit 130 does not output a trip signal. Therefore, inverter circuit 120 continues power conversion.

[0042] On the other hand, when any of the phase currents is equal to or lower than the negative overcurrent protection threshold or equal to or higher than the positive overcurrent protection threshold, a cutoff signal is output (step S17). Then, the buffer circuit 140 cuts off the gate drive signal from the drive control device 150 (step S18). As a result, the inverter circuit 120 stops power conversion.

[0043] As described above, the comparison unit 130 of the motor control device 100 according to the second embodiment individually compares the positive and negative portions of the phase currents of the U, V, and W phases with the corresponding +-side overcurrent protection threshold and --side overcurrent protection threshold, respectively, to determine whether or not to output a tripping signal. Therefore, in addition to the effects of the first embodiment, even when the phase currents flowing through the motor 300 are unbalanced, it is possible to more accurately determine whether or not to output a tripping signal while reducing the number of comparators. This makes it possible to obtain a more reliable motor control device 100.

[0044] Embodiment 3 In the above-described first and second embodiments, the current detection unit 160 has been described as detecting phase currents, but this is not limiting. The current detection unit 160 may, for example, detect a current returning from the electric motor 300 to the electric motor control device 100, a shunt resistor inserted in a DC bus path, or a shunt current flowing through three shunt resistors inserted between each phase and the DC bus path, and compare the detected currents with the overcurrent protection threshold value in the comparison unit 130.

[0045] Embodiment 4 Fig. 7 is a diagram showing the configuration of an air conditioner 1 according to embodiment 4. Here, the air conditioner 1 will be described as an example of a refrigeration cycle device that has an electric motor control device 100 and drives an electric motor 300. Here, the configuration of the air conditioner 1 in Fig. 7 is one example, and the configuration of the refrigeration cycle device is not particularly limited.

[0046] 7, an outdoor unit (outdoor unit) 10 and an indoor unit (indoor unit) 20 are connected by refrigerant piping 30 to form a refrigerant circuit that circulates refrigerant. The outdoor unit 10 has a compressor 11 equipped with a motor 300, a four-way valve 12, an outdoor heat exchanger 13, an expansion valve 14, and an outdoor blower 15. The indoor unit 20 has an indoor heat exchanger 21.

[0047] The compressor 11 has the electric motor 300 according to the first and second embodiments. The compressor 11 compresses and discharges the sucked refrigerant when the electric motor 300 is driven. Here, the drive frequency of the electric motor 300 can be arbitrarily changed by the electric motor control device 100 described in the first and second embodiments, and the capacity of the compressor 11 can be finely changed. The four-way valve 12 is a flow path switching valve that switches the flow of the refrigerant depending on whether the operation is cooling or heating.

[0048] The outdoor heat exchanger 13 exchanges heat between the refrigerant and air (outdoor air). During heating operation, the outdoor heat exchanger 13 functions as an evaporator, evaporating and vaporizing the refrigerant. During cooling operation, the outdoor heat exchanger 13 functions as a condenser, condensing and liquefying the refrigerant. The outdoor blower 15 sends outdoor air to the outdoor heat exchanger 13, promoting heat exchange between the outdoor air and the refrigerant.

[0049] The expansion valve 14, such as a throttle device acting as a pressure reducing device, is a refrigerant flow rate regulating valve that reduces the pressure of the refrigerant to expand it and control the flow rate of the refrigerant. For example, if the expansion valve 14 is configured to include an electronic expansion valve or the like, its opening degree is adjusted based on instructions from a control device (not shown). The indoor heat exchanger 21 exchanges heat between the air to be conditioned and the refrigerant. During heating operation, the indoor heat exchanger 21 functions as a condenser, condensing and liquefying the refrigerant. During cooling operation, the indoor heat exchanger 21 functions as an evaporator, evaporating and vaporizing the refrigerant. The indoor blower 22 sends the air to be conditioned to the indoor heat exchanger 21, promoting heat exchange between the air and the refrigerant.

[0050] The air conditioning apparatus 1 also has an air conditioning control device 50 that controls the entire apparatus. In the fourth embodiment, the air conditioning control device 50 sends a speed command signal to the drive control device 150 in order to control the rotation speed of the compressor 11 in particular. The drive control device 150 drives the electric motor 300 at a drive frequency based on the speed command signal. Here, the air conditioning control device 50 and the drive control device 150 are separate control devices, but they may also be configured as an integrated device.

[0051] As described above, according to the air conditioning device 1 of embodiment 4, by being configured to have the motor control device 100 described in embodiments 1 to 3, it is possible to perform more reliable operation while protecting the compressor 11.

[0052] Various aspects of the present disclosure are summarized below as appendices.

[0053] (Appendix 1) a current sensor for detecting a current flowing through the electric motor; a temperature sensor for detecting a temperature in the electric motor; a control device that determines an overcurrent protection threshold for stopping the electric motor based on the temperature detected by the temperature sensor; a comparison unit that outputs a trip signal based on a comparison between the current and the overcurrent protection threshold; a protection circuit that stops the motor when the shutdown signal is sent; An electric motor control device comprising: (Appendix 2) 2. The motor control device according to claim 1, wherein the control device has a D / A port unit that converts the overcurrent protection threshold into an analog signal and sends the analog signal to the comparison unit. (Appendix 3) the current sensor detects a phase current flowing through each phase of the electric motor; the control device determines a positive side overcurrent protection threshold and a negative side overcurrent protection threshold corresponding to a positive portion and a negative portion of the phase current, respectively; The motor control device according to claim 1 or 2, wherein the comparison unit outputs the trip signal by comparing the positive portion of the phase current flowing through each phase with the positive-side overcurrent protection threshold and by comparing the negative portion of the phase current with the negative-side overcurrent protection threshold. (Appendix 4) The motor control device according to claim 3, wherein the comparison unit outputs the shutdown signal when the positive portion of one or more of the phase currents is greater than the positive side overcurrent protection threshold or the negative portion is less than the negative side overcurrent protection threshold. (Appendix 5) 5. The electric motor control device according to claim 1, wherein the temperature sensor detects a temperature of a permanent magnet in the electric motor. (Appendix 6) A refrigeration cycle device comprising the motor control device according to any one of Supplementary notes 1 to 5. [Industrial Applicability]

[0054] In the fourth embodiment, the air conditioner 1 has been described as an example of a refrigeration cycle device, but the present invention is not limited to this. The motor control device 100 according to the first to third embodiments can also be applied to other refrigeration cycle devices such as freezers, washer-dryers, refrigerators, dehumidifiers, heat pump water heaters, and showcases. [Explanation of symbols]

[0055] 1 air conditioning device, 10 outdoor unit, 11 compressor, 12 four-way valve, 13 outdoor heat exchanger, 14 expansion valve, 15 outdoor blower, 20 indoor unit, 21 indoor heat exchanger, 22 indoor blower, 30 refrigerant piping, 50 device control device, 100 motor control device, 110 rectifier circuit, 111 rectifier, 112 reactor, 113 smoothing capacitor, 120 inverter circuit, 121 switching element, 122 diode, 130 comparison unit, 131 current comparator, 132 U phase + side comparator, 133 U phase - side comparator, 134 W phase + side comparator, 135 W phase - side comparator, 136 V phase + side comparator, 137 V phase - side comparator, 140 buffer circuit, 150 drive control device, 151 inverter control unit, 152 Overcurrent protection threshold setting unit, 153 threshold memory unit, 154 D / A port unit, 160 current detection unit, 161 phase current sensor, 162 U-phase current sensor, 163 W-phase current sensor, 171 magnet temperature sensor, 180 V-phase current detection circuit, 200 three-phase AC power supply, 300 electric motor.

Claims

1. a current sensor for detecting a current flowing through the electric motor; a temperature sensor for detecting a temperature in the electric motor; a control device that determines an overcurrent protection threshold for stopping the electric motor based on the temperature detected by the temperature sensor; a comparison unit that outputs a trip signal based on a comparison between the current and the overcurrent protection threshold; a protection circuit that stops the motor when the shutdown signal is sent; An electric motor control device comprising:

2. 2. The motor control device according to claim 1, wherein the control device has a D / A port unit that converts the overcurrent protection threshold into an analog signal and sends the analog signal to the comparison unit.

3. the current sensor detects a phase current flowing through each phase of the electric motor; the control device determines a positive side overcurrent protection threshold and a negative side overcurrent protection threshold corresponding to a positive portion and a negative portion of the phase current, respectively; 3. The motor control device according to claim 1, wherein the comparison unit outputs the trip signal by comparing the positive portion of the phase current flowing through each phase with the positive-side overcurrent protection threshold and by comparing the negative portion of the phase current with the negative-side overcurrent protection threshold.

4. 4. The motor control device according to claim 3, wherein the comparison unit outputs the shutdown signal when the positive portion of one or more of the phase currents is greater than the positive side overcurrent protection threshold or the negative portion is less than the negative side overcurrent protection threshold.

5. 3. The motor control device according to claim 1, wherein the temperature sensor detects the temperature of a permanent magnet in the motor.

6. A refrigeration cycle device comprising the motor control device according to claim 1 or 2.

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