Power conversion device, refrigeration cycle device using the same, and leakage inductance calculation method

Abstract

This power conversion device comprises: a voltage application means that converts DC voltage to AC voltage and that supplies the converted AC voltage to a three-phase motor; a current detection means for detecting current flowing through the motor; and a control device that controls the voltage application means. The control device calculates leakage inductance in the motor, on the basis of the current detected by the current detection means, in a state where the wire connection state of the motor is in a V-shaped Δ-wire connection for measurement in which one connecting section of the Δ-wire connection has been removed.

Description

[Technical field]

[0001] The present disclosure relates to a power conversion device that converts supplied power into power suitable for a motor driven by a three-phase AC voltage, a refrigeration cycle device using the same, and a leakage inductance calculation method. [Background technology]

[0002] Conventionally, there is known a power conversion device that converts a commercial AC power source into an arbitrary frequency and an arbitrary voltage using a rectifier circuit and an inverter circuit, and supplies the converted voltage to a load such as an electric motor (for example, see Patent Document 1). Generally, three-phase electric motors driven by AC voltage are connected in either a delta or a wye connection, and a delta-connected electric motor requires a lower voltage to drive than a wye-connected electric motor. Therefore, taking advantage of the fact that the power required to drive the motor differs depending on the connection state, electric motors that can be switched between a wye connection and a delta connection to improve drive efficiency are used mainly in large-capacity fields. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-69897 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in a motor that can switch the connection state, leakage current caused by leakage inductance can become a problem in the delta connection state. In order to understand the characteristics of the leakage current and take measures, it is necessary to know the value of the leakage inductance, but since the leakage inductance is small compared to the effective inductance, it is difficult to accurately measure the leakage inductance of a delta connection motor.

[0005] The present disclosure has been made in consideration of the problems in the conventional technology described above, and aims to provide a power conversion device capable of accurately measuring the leakage inductance of a Δ-connected electric motor, a refrigeration cycle device using the same, and a leakage inductance calculation method. [Means for solving the problem]

[0006] The power conversion device of the present disclosure comprises a voltage application means for converting a DC voltage into an AC voltage and supplying the converted AC voltage to a three-phase electric motor, a current detection means for detecting a current flowing through the electric motor, and a control device for controlling the voltage application means, and the control device calculates the leakage inductance in the electric motor based on the current detected by the current detection means when the connection state of the electric motor is a V-shaped measurement delta connection in which one connection part of the delta connection is removed.

[0007] A refrigeration cycle device according to the present disclosure includes the above-described power conversion device.

[0008] The leakage inductance calculation method according to the present disclosure is a leakage inductance calculation method for calculating the leakage inductance of a three-phase electric motor, in which the connection state of the windings of the electric motor is a V-shaped measurement delta connection in which one connection part of the delta connection is removed, and the leakage inductance in the electric motor is calculated based on the current flowing through the electric motor to which an AC voltage is applied. Effect of the Invention

[0009] According to the present disclosure, the connection state of the motor is a measurement delta connection, and the current flowing through the motor is detected in the measurement delta connection state. Then, the leakage inductance is calculated based on the detected current, so that the leakage inductance of the delta-connected motor can be accurately measured. [Brief description of the drawings]

[0010] [Figure 1] 1 is a circuit diagram showing an example of a configuration of a power conversion device according to a first embodiment. [Diagram 2] 2 is a hardware configuration diagram showing an example of the configuration of the control device in FIG. 1. [Diagram 3] 1. FIG. 4 is a hardware configuration diagram showing another example of the configuration of the control device in FIG. [Figure 4] FIG. 11 is a circuit diagram when the motor is in an operational Δ connection state. [Diagram 5] FIG. 11 is a circuit diagram when the connection state of the motor is a measurement Δ connection. [Figure 6] 5 is a flowchart showing an example of a flow of a leakage inductance measurement process according to the first embodiment. [Figure 7] FIG. 4 is a schematic diagram for explaining the state of a switching element of a voltage application means in a first connection state. [Figure 8] FIG. 4 is a circuit diagram for illustrating a current flow in a first connection state. [Figure 9] 6 is a schematic diagram for explaining the state of a switching element of a voltage application means in a second connection state. FIG. [Figure 10] FIG. 11 is a circuit diagram for illustrating a current flow in a second connection state. [Figure 11] 10 is a schematic diagram for explaining the state of a switching element of a voltage application means in a third connection state. FIG. [Figure 12] FIG. 11 is a circuit diagram for illustrating a current flow in a third connection state. [Figure 13] FIG. 11 is a configuration diagram showing an example of the configuration of an air conditioning apparatus according to embodiment 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments, and various modifications can be made without departing from the spirit of the present disclosure. In addition, in each drawing, the same reference numerals are used to denote the same or equivalent parts, and this is common throughout the specification. Furthermore, the highs and lows of voltage and current are not determined in relation to absolute values, but are determined relatively in the state and operation of the device, etc.

[0012] Embodiment 1 Hereinafter, a description will be given of the power conversion device according to the present embodiment 1. The power conversion device according to the present embodiment 1 converts supplied power into power suitable for driving an electric motor capable of switching between Y connection and Δ connection.

[0013] [Configuration of power conversion device 100] Fig. 1 is a circuit diagram showing an example of the configuration of a power conversion device according to the present embodiment 1. As shown in Fig. 1, the power conversion device 100 includes a voltage application means 1, a current detection means 2, a connection switching device 3, and a control device 4. In addition, a DC voltage source 200 and an electric motor 300, which is a load, are connected to the power conversion device 100.

[0014] The DC voltage source 200 supplies a DC voltage V dc The output terminal of DC voltage source 200 is connected to a positive bus 5 and a negative bus 6 which are buses of power conversion device 100. Positive bus 5 is a bus on the high potential side, and negative bus 6 is a bus on the low potential side. Motor 300 is a three-phase motor that is driven by AC voltage converted by power conversion device 100 and has U-phase, V-phase, and W-phase stator windings.

[0015] The voltage application means 1 is connected to a positive bus 5 and a negative bus 6, which are output terminals of a DC voltage source 200. The voltage application means 1 receives a DC voltage V dcThe voltage application means 1 is connected to an electric motor 300 and supplies the converted AC voltage to the electric motor 300.

[0016] The voltage application means 1 is, for example, a three-phase voltage type inverter, and is configured as a full bridge circuit having six switching elements 11 to 16. Specifically, in the voltage application means 1, two switching elements are connected in series to form a series body. Then, three such series bodies are connected in parallel to form a full bridge circuit. In addition, a freewheeling diode is connected in anti-parallel to each of the switching elements 11 to 16.

[0017] The voltage application means 1 outputs a pulsed AC voltage that is a PWM (Pulse Width Modulation) voltage by controlling these switching elements 11-16 by a voltage command supplied from the control device 4. The switching elements 11-16 perform on and off operations independently of each other based on the voltage command that is a switching signal supplied from the control device 4.

[0018] The current detection means 2 detects the current output from the voltage application means 1 and supplied to the electric motor 300, and outputs the detected current value as current information. In the present embodiment 1, the current detection means 2 is configured by providing a shunt resistor on the negative bus 6 of the voltage application means 1. Note that the current detection means 2 is not limited to a shunt resistor, and for example, a current sensor using an instrument current transformer called a CT (Current Transformer) may be used.

[0019] The connection switching device 3 has switches 31 to 33 provided according to the number of phases of the electric motor 300. The connection switching device 3 switches the connection state of each phase of the electric motor 300 between Y connection or Δ connection by performing switching operations of the switches 31 to 33 based on a switching command from the control device 4. The switches 31 to 33 may be configured, for example, by mechanical relays or semiconductor switches.

[0020] The control device 4 controls the entire power conversion device 100 based on an external command or information from various detection means and sensors provided in the power conversion device 100. In addition, in the present embodiment 1, the control device 4 performs a leakage inductance measurement process for measuring a value of leakage inductance in the electric motor 300. The leakage inductance measurement process will be described later in detail.

[0021] The control device 4 includes a voltage control unit 41, a switching control unit 42, and a measurement unit 43. The control device 4 is configured such that various functions are realized by executing software on a calculation device such as a microcomputer, or is configured with hardware such as a circuit device that realizes various functions.

[0022] Based on an operation command such as a speed command or a torque command input from the outside, the voltage control unit 41 generates a voltage command for controlling the switching elements 11-16 of the voltage application means 1. Then, the voltage control unit 41 outputs the generated voltage command to the voltage application means 1.

[0023] At this time, the control device 4 generates a voltage command using various control methods so that an appropriate AC voltage is supplied from the voltage application means 1 to the electric motor 300. For example, constant V / f control, vector control, direct torque control, etc. are used as the control method. Constant V / f control is a control method that outputs a voltage proportional to the operating frequency of the electric motor 300. Vector control is a control method that controls the current flowing through the electric motor 300 using a rotating coordinate system. Direct torque control is a control method that controls the magnetic flux and torque of the electric motor 300.

[0024] The switching control unit 42 generates a switching command for switching the switches 31 to 33 of the connection switching device 3. Then, the switching control unit 42 outputs the generated switching command to the connection switching device 3.

[0025] During leakage inductance measurement processing, the measurement unit 43 calculates the leakage inductance based on the current information supplied from the current detection means 2. The method of calculating the leakage inductance will be described later in detail.

[0026] Fig. 2 is a hardware configuration diagram showing an example of the configuration of the control device in Fig. 1. When the various functions of the control device 4 are executed by hardware, the control device 4 in Fig. 1 is configured by a processing circuit 51 as shown in Fig. 2. The functions of the voltage control unit 41, the switching control unit 42, and the measurement unit 43 in Fig. 1 are realized by the processing circuit 51.

[0027] When each function is executed by hardware, the processing circuit 51 corresponds to, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination of these. The functions of each of the voltage control unit 41, the switching control unit 42, and the measurement unit 43 may be realized by the processing circuit 51, or the functions of each unit may be realized by one processing circuit 51.

[0028] Fig. 3 is a hardware configuration diagram showing another example of the configuration of the control device in Fig. 1. When the various functions of the control device 4 are executed by software, the control device 4 in Fig. 1 is configured with a processor 52 and a memory 53, as shown in Fig. 3. The functions of the voltage control unit 41, the switching control unit 42, and the measurement unit 43 are realized by the processor 52 and the memory 53.

[0029] When each function is executed by software, the functions of voltage control unit 41, switching control unit 42, and measurement unit 43 are realized by software, firmware, or a combination of software and firmware. The software and firmware are written as programs and stored in memory 53. Processor 52 realizes the function of each unit by reading and executing the programs stored in memory 53.

[0030] For example, non-volatile or volatile semiconductor memories such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable and Programmable ROM), and EEPROM (Electrically Erasable and Programmable ROM) are used as the memory 53. In addition, for example, removable recording media such as magnetic disks, flexible disks, optical disks, CDs (Compact Discs), MDs (Mini Discs), and DVDs (Digital Versatile Discs) may be used as the memory 53.

[0031] [Connection state of electric motor 300] Here, the connection state of the electric motor 300 will be described. When the connection state of the electric motor 300 is a Y-connection state, the line voltage is defined as "V Y " and the current flowing into the stator winding is "I Y ". In addition, the line voltage when the connection state of the electric motor 300 is set to the Δ connection state is set to "V Δ " and the current flowing into the stator winding is "I Δ "

[0032] If we assume that the voltages applied to the stator windings of each phase are equal, then the voltage V Y and voltage V Δ The relationship between the current I Y and current I Δ The relationship between them satisfies equation (2). V Δ =V Y / √3 (1) I Δ =√3×I Y (2)

[0033] Voltage V in Y-connection state Y and current I Y and the voltage V in the Δ-connected state Δ and current I Δand have the relationship of formula (1) and formula (2), the electric power supplied to the motor 300 in the Y-connection state and the Δ-connection state are equal to each other. In other words, when the electric powers supplied to the motor 300 are equal to each other, the current flowing into the stator winding is larger in the Δ-connection state than in the Y-connection state, and the voltage required to drive the motor 300 is lower.

[0034] For this reason, when driving the electric motor 300, it is possible to select the connection state according to the load conditions. For example, at low load, the electric motor 300 operates at low speed in the Y connection state, and at high load, the electric motor 300 operates at high speed in the Δ connection state. This makes it possible to improve the efficiency at low load and to increase the output at high load.

[0035] However, as described in the Background Art section, since leakage inductance is small compared to effective inductance, it is difficult to accurately measure leakage inductance in a motor in a Δ connection state. Therefore, in order to accurately measure the leakage inductance of a Δ-connected motor, the power conversion device 100 according to the first embodiment performs leakage inductance measurement processing by setting the connection state of the motor 300 to a special Δ connection.

[0036] Fig. 4 is a circuit diagram when the motor is connected in an operating Δ connection. Fig. 5 is a circuit diagram when the motor is connected in a measuring Δ connection. Note that in Fig. 4 and Fig. 5, the connection switching device 3 and the control device 4 are omitted so that the connection state can be easily understood.

[0037] The operational delta connection is a normal delta connection, and as shown in Fig. 4, the stator windings between the phases are completely delta connected. In this case, one end of the stator winding between the U and V phases is connected between the switching elements 11 and 12 of the voltage application means 1, and the other end is connected between the switching elements 13 and 14. Also, one end of the stator winding between the V and W phases is connected between the switching elements 13 and 14 of the voltage application means 1, and the other end is connected between the switching elements 15 and 16. Furthermore, one end of the stator winding between the W and U phases is connected between the switching elements 15 and 16 of the voltage application means 1, and the other end is connected between the switching elements 11 and 12.

[0038] On the other hand, as shown in FIG. 5, the measurement Δ connection is an incomplete Δ connection in which one end of one stator winding is removed from among the stator windings between the phases. That is, the measurement Δ connection is a so-called V-shaped connection in which one connection part of the Δ connection is removed. In the example shown in FIG. 5, one end of the stator winding between the WU phases is removed, and a V-shape is formed by the stator windings between the UV phases and the VW phases. Specifically, one end of the stator winding between the UV phases is connected between the switching element 11 and the switching element 12 of the voltage application means 1, and the other end is connected between the switching element 13 and the switching element 14. Also, one end of the stator winding between the VW phases is connected between the switching element 13 and the switching element 14 of the voltage application means 1, and the other end is connected between the switching element 15 and the switching element 16. On the other hand, one end of the WU interphase stator winding is connected between switching element 15 and switching element 16 of voltage application means 1, but the other end is not connected anywhere and is in a disconnected state.

[0039] When such a measurement Δ connection is used as the connection state of the motor 300, the switching elements 11-16 of the voltage application means 1 in the power conversion device 100 are controlled to apply a voltage between specific phases of the motor 300. Then, by measuring the current that flows when a voltage is applied between the specific phases, the inductance value at that time can be derived.

[0040] [Leakage inductance measurement process] In the first embodiment, when the leakage inductance measurement process is performed, the connection state of the electric motor 300 is switched from the operation Δ connection of Fig. 4 to the measurement Δ connection of Fig. 5. Then, with the connection state of the electric motor 300 set to the measurement Δ connection, the connection state between the power conversion device 100 and the electric motor 300 is switched, and the leakage inductance measurement process is performed.

[0041] 6 is a flowchart showing an example of the flow of leakage inductance measurement processing according to the present embodiment 1. The leakage inductance measurement processing according to the present embodiment 1 is performed in a state where the electric motor 300 is stopped in order to prevent the influence of a speed electromotive force generated by the operation of the electric motor 300.

[0042] First, in step S1, the connection state of the electric motor 300 is switched to the measurement Δ connection. In this case, the switching control unit 42 of the control device 4 outputs a switching command to the connection switching device 3 and switches the switches 31 to 33 so that the connection state of the electric motor 300 becomes the measurement Δ connection shown in FIG.

[0043] Next, in step S2, the connection between the power conversion device 100 and the electric motor 300 is set to a first connection state. The first connection state is a connection state for allowing a current to flow through the stator windings between the U and V phases.

[0044] Fig. 7 is a schematic diagram for explaining the states of the switching elements of the voltage application means in the first connection state. Fig. 7 shows the setting states of the switching elements 11-16 of the voltage application means 1 for bringing the connection between the power conversion device 100 and the electric motor 300 into the first connection state in response to a voltage command from the voltage control unit 41.

[0045] Fig. 8 is a circuit diagram for explaining the flow of current in the first connection state. In Fig. 8, the thick lines in the circuit diagram indicate the current paths in the first connection state when switching elements 11 to 16 are set as shown in Fig. 7. The arrows in the circuit diagram indicate the current I1 flowing through the current paths.

[0046] 7, the voltage control unit 41 outputs a voltage command to the voltage application means 1 to turn on the switching elements 11 and 14 and turn off the switching elements 12, 13, 15 and 16, thereby switching the switching elements 11 to 16. As a result, a pulsed voltage is applied between the UV phases of the motor 300, and a current I1 flows.

[0047] The current detection means 2 detects the negative DC bus current I1, which is a current between the U and U phases that flows in the negative bus 6 as a result of application of a pulsed voltage. Then, when the negative DC bus current I1 is detected, the voltage control unit 41 outputs a voltage command to the voltage application means 1 to turn off all the switching elements 11 to 16, thereby making the current flowing in the current detection means 2 sufficiently small.

[0048] 6, the connection between the power conversion device 100 and the electric motor 300 is set to the second connection state. The second connection state is a connection state for allowing a current to flow through the stator winding between the V and W phases.

[0049] Fig. 9 is a schematic diagram for explaining the states of the switching elements of the voltage application means in the second connection state. Fig. 9 shows the setting states of the switching elements 11-16 of the voltage application means 1 for bringing the connection between the power conversion device 100 and the electric motor 300 into the second connection state in response to a voltage command from the voltage control unit 41.

[0050] Fig. 10 is a circuit diagram for explaining the flow of current in the second connection state. In Fig. 10, the thick lines in the circuit diagram indicate the current paths in the second connection state when switching elements 11 to 16 are set as shown in Fig. 9. The arrows in the circuit diagram indicate the current I2 flowing through the current paths.

[0051] 9, the voltage control unit 41 outputs a voltage command to the voltage application means 1 to turn on the switching elements 13 and 16 and turn off the switching elements 11, 12, 14 and 15, thereby switching the switching elements 11 to 16. As a result, a pulsed voltage is applied between the V and W phases of the electric motor 300, and a current I2 flows.

[0052] The current detection means 2 detects the negative DC bus current I2, which is a current between the V and W phases that flows in the negative bus 6 as a result of the application of a pulsed voltage. Then, when the negative DC bus current I2 is detected, the voltage control unit 41 outputs a voltage command to the voltage application means 1 to turn off all the switching elements 11 to 16, and makes the current flowing in the current detection means 2 sufficiently small.

[0053] In step S4 of Fig. 6, the connection between the power conversion device 100 and the electric motor 300 is set to a third connection state. The third connection state is a connection state for allowing current to flow through the stator winding between the W and U phases. Here, in the measurement delta connection, the stator winding between the W and U phases is in a disconnected state. Therefore, in the third connection state, current flows through the stator winding between the V and W phases and the stator winding between the UV phases.

[0054] Fig. 11 is a schematic diagram for explaining the states of the switching elements of the voltage application means in the third connection state. Fig. 11 shows the setting states of the switching elements 11-16 of the voltage application means 1 for bringing the connection between the power conversion device 100 and the electric motor 300 into the third connection state in response to a voltage command from the voltage control unit 41.

[0055] Fig. 12 is a circuit diagram for explaining the flow of current in the third connection state. In Fig. 12, the thick lines in the circuit diagram indicate the current paths in the third connection state when switching elements 11 to 16 are set as shown in Fig. 11. The arrows in the circuit diagram indicate the current I3 flowing through the current paths.

[0056] 11, the voltage control unit 41 outputs a voltage command to the voltage application means 1 to turn on the switching elements 12 and 15 and turn off the switching elements 11, 13, 14 and 16, thereby switching the switching elements 11 to 16. As a result, a pulsed voltage is applied between the W and U phases of the electric motor 300, and a current I3 flows.

[0057] The current detection means 2 detects the negative DC bus current I3, which is a current between the W and U phases that flows in the negative bus 6 as a result of the application of a pulsed voltage. Then, when the negative DC bus current I3 is detected, the voltage control unit 41 outputs a voltage command to the voltage application means 1 to turn off all the switching elements 11 to 16, and makes the current flowing in the current detection means 2 sufficiently small.

[0058] Next, in step S5 of FIG. 6, the measurement unit 43 measures the DC voltage V dc and the negative DC bus currents I1 to I3 detected by the current detection means 2, the leakage inductance is calculated. Generally, when a voltage V is input in a step to an RL load consisting of a resistance R and an inductance L, the response of the current I rises with a slope of "voltage V / inductance L". Therefore, the inductance L can be calculated from "V / I".

[0059] In the first embodiment, in the first connection state in step S2, a current I1 flows only through the stator winding between the U and V phases in the electric motor 300. Therefore, the inductance L1 of the current path at this time is expressed as in equation (3). In equation (3), "L a " indicates the average value of the effective inductance per phase of the motor 300. a" indicates leakage inductance per phase. L1=I1 / V dc =L a +l a (3)

[0060] Moreover, in the second connection state in step S3, a current flows only through the stator winding between the V and W phases in the electric motor 300. Therefore, the inductance L2 of the current path at this time is expressed as in equation (4). L2=I2 / V dc =L a +l a (4)

[0061] On the other hand, in the third connection state in step S4, current flows through both the stator windings between the UV phases and between the VW phases in the electric motor 300. Furthermore, mutual induction acts in the respective stator windings in a direction that weakens the magnetic flux of each other. Therefore, the inductance L3 of the current path at this time is expressed as in equation (5). In equation (5), "M" represents the mutual inductance between the phases, and "M=L a / 2". L3=(L a +l a -M) x 2 =(L a +l a -L a / 2)×2 =L a +2l a (5)

[0062] Therefore, the currents I1 and I3 obtained in steps S2 and S4 and the DC voltage V dc From this, the leakage inductance l a is calculated based on equation (6) by using equations (3) and (5). Note that the leakage inductance l a may be calculated using I2 instead of I1. l a =L3-L1=V dc / (I3-I1) ···(6)

[0063] Finally, in step S6 in Fig. 6, the connection state of the electric motor 300 is switched to the operational Δ connection state shown in Fig. 4. Then, a series of processes is completed.

[0064] In this way, in the leakage inductance measurement process, the connection state of the motor 300 is set as a measurement delta connection, and the leakage inductance is calculated based on the current I1 flowing between the U and U phases or the current I2 flowing between the V and W phases, and the current I3 flowing between the W and U phases. At this time, when calculating the current I3, attention is paid to the mutual induction effect, so that it is possible to accurately calculate a leakage inductance that is small compared to the effective inductance. The calculated leakage inductance can be used, for example, when designing the next or subsequent motors.

[0065] Furthermore, the calculated leakage inductance may change depending on the usage time of the electric motor 300. Therefore, the changing leakage inductance may be used to detect an abnormality such as the life or failure of the electric motor 300 or the power conversion device 100. In this case, the control device 4 of the power conversion device 100 presets a threshold value for the leakage inductance, and determines that an abnormality has occurred in the electric motor 300 or the power conversion device 100 when the calculated leakage inductance exceeds the threshold value.

[0066] As described above, in the power conversion device 100 according to the first embodiment, the connection state of the three-phase electric motor 300, which can be switched between a Y connection and a Δ connection, is set to a V-shaped measurement Δ connection in which one connection part of the Δ connection is removed. Then, the leakage inductance of the electric motor 300 is calculated based on the current flowing through the electric motor 300 in the measurement Δ connection state. This makes it possible to accurately calculate the leakage inductance of the electric motor 300.

[0067] Furthermore, since the leakage inductance can be calculated accurately in this manner, it is expected that a failure of the electric motor 300 can be predicted, for example, by periodically acquiring the leakage inductance.

[0068] Embodiment 2 Next, a description will be given of the present embodiment 2. In the present embodiment 2, an example in which the power conversion device 100 described in the embodiment 1 is applied to an air conditioner will be described.

[0069] [Configuration of air conditioning device 500] Fig. 13 is a configuration diagram showing an example of the configuration of an air conditioner according to Embodiment 2. An air conditioner 500 in Fig. 13 performs cooling operation and heating operation by using a heat pump system.

[0070] 13, air conditioning apparatus 500 is composed of outdoor unit 500A including compressor 501, refrigerant flow switching device 502, outdoor heat exchanger 503, and expansion valve 504, and indoor unit 500B including indoor heat exchanger 505. In air conditioning apparatus 500, compressor 501, refrigerant flow switching device 502, outdoor heat exchanger 503, expansion valve 504, and indoor heat exchanger 505 are sequentially connected by refrigerant piping to form a refrigerant circuit in which refrigerant circulates through the refrigerant piping.

[0071] Of these, compressor 501 has compression element 501a that compresses the refrigerant, and motor M as electric motor 300 that is connected to compression element 501a and is supplied with power from power conversion device 100. Power conversion device 100 is the device according to the above-mentioned embodiment 1, and receives power from DC voltage source 200 that is a power source, and supplies the converted power to motor M to rotate motor M.

[0072] The refrigerant flow switching device 502 is, for example, a four-way valve, and switches between cooling operation and heating operation by switching the direction of refrigerant flow. The outdoor heat exchanger 503 exchanges heat between the refrigerant and the outside air. The outdoor heat exchanger 503 functions as a condenser during cooling operation and as an evaporator during heating operation. The expansion valve 504 expands the refrigerant. The indoor heat exchanger 505 exchanges heat between the refrigerant and the indoor air in the space to be air-conditioned. The indoor heat exchanger 505 functions as an evaporator during cooling operation and as a condenser during heating operation.

[0073] [Operation of air conditioning device 500] Next, the operation of air conditioner 500 according to the second embodiment will be described with reference to Fig. 13. Here, cooling operation will be described as an example. When performing cooling operation, refrigerant flow path switching device 502 is assumed to have switched the flow path in advance so that refrigerant discharged from compressor 501 flows toward outdoor heat exchanger 503, and refrigerant flowing out of indoor heat exchanger 505 flows toward compressor 501. At this time, outdoor heat exchanger 503 functions as a condenser, and indoor heat exchanger 505 functions as an evaporator.

[0074] When the motor M of the compressor 501 is rotationally driven by the power conversion device 100, the compression element 501a of the compressor 501 connected to the motor M compresses a low-temperature, low-pressure refrigerant, and the compressor 501 discharges a high-temperature, high-pressure gas refrigerant. The high-temperature, high-pressure gas refrigerant discharged from the compressor 501 passes through the refrigerant flow switching device 502 and flows into the outdoor heat exchanger 503 functioning as a condenser.

[0075] The high-temperature, high-pressure gas refrigerant that flows into the outdoor heat exchanger 503 condenses while exchanging heat with the outside air and releasing heat, becoming a high-pressure liquid refrigerant that flows out of the outdoor heat exchanger 503. The high-pressure liquid refrigerant that flows out of the outdoor heat exchanger 503 is expanded and reduced in pressure by the expansion valve 504, becoming a low-temperature, low-pressure gas-liquid two-phase refrigerant, and flows into the indoor heat exchanger 505 that functions as an evaporator.

[0076] The low-temperature, low-pressure two-phase gas-liquid refrigerant that flows into indoor heat exchanger 505 exchanges heat with the air in the space to be air-conditioned, absorbing heat and evaporating, thereby cooling the indoor air, and becomes low-temperature, low-pressure gas refrigerant, which flows out of indoor heat exchanger 505. The low-temperature, low-pressure gas refrigerant that flows out of indoor heat exchanger 505 is sucked into compressor 501 via refrigerant flow switching device 502, and compressed again. The above-mentioned operations are repeated thereafter.

[0077] 13 shows an example in which the power conversion device 100 according to the first embodiment is applied to the compressor 501 of the air-conditioning device 500, but the present invention is not limited to this and may be applied, for example, to a power source for driving a fan (not shown) that blows air to the outdoor heat exchanger 503. The power conversion device 100 may also be applied, for example, to a heat pump device using the compressor 501, a refrigeration device, and other general refrigeration cycle devices.

[0078] As described above, in the air conditioning apparatus 500 according to the second embodiment, the compressor 501 provided in the refrigerant circuit is driven by power supplied from the power conversion apparatus 100. The power conversion apparatus 100 measures the leakage inductance in a state where the motor M, which is the electric motor 300 of the compressor 501, is stopped, so that it is possible to accurately measure the leakage inductance in the Δ-connected electric motor 300, as in the first embodiment.

[0079] Although the first and second embodiments have been described above, the present disclosure is not limited to the above-mentioned first and second embodiments, and various modifications and applications are possible without departing from the gist of the present disclosure. In the first embodiment, a DC voltage source 200 is connected to a power conversion device 100, and a DC voltage V dc However, the present invention is not limited to this example. For example, the power conversion device 100 may be connected to a commercial AC power supply that is a three-phase AC power supply.

[0080] In this case, however, the power conversion device 100 is provided with a rectifier circuit and a smoothing capacitor in the upstream of the voltage application means 1. As a result, the AC voltage supplied from the AC power source is rectified by the rectifier circuit, and the rectified DC voltage is smoothed by the smoothing capacitor. Then, the DC voltage V output from the DC voltage source 200 is supplied to the downstream voltage application means 1. dc A DC voltage equivalent to

[0081] In the first embodiment, the case where one of both ends of the stator winding between the W and U phases is in a disconnected state has been described, but this is not limited to this example. For example, in the measurement delta connection, one of both ends of the stator winding between the U and V phases may be in a disconnected state, or one of both ends of the stator winding between the V and W phases may be in a disconnected state.

[0082] Furthermore, the power conversion device 100 has been described as controlling the driving of one electric motor 300 as a load with one voltage application means 1, but this is not limited to this example. For example, the power conversion device 100 may control the driving of a plurality of loads (electric motors) with one voltage application means 1. [Explanation of symbols]

[0083] 1 voltage application means, 2 current detection means, 3 connection switching device, 4 control device, 5 positive busbar, 6 negative busbar, 11, 12, 13, 14, 15, 16 switching elements, 31, 32, 33 switches, 41 voltage control unit, 42 switching control unit, 43 measurement unit, 51 processing circuit, 52 processor, 53 memory, 100 power conversion device, 200 DC voltage source, 300 motor, 500 air conditioning device, 500A outdoor unit, 500B indoor unit, 501 compressor, 501a compression element, 502 refrigerant flow switching device, 503 outdoor heat exchanger, 504 expansion valve, 505 indoor heat exchanger.

Claims

1. a voltage application means for converting a DC voltage into an AC voltage and supplying the converted AC voltage to a three-phase motor; A current detection means for detecting a current flowing through the electric motor; A control device for controlling the voltage application means; Equipped with The control device includes: In a state where the connection state of the motor is a V-shaped measurement delta connection in which one connection portion of the delta connection is removed, a leakage inductance in the motor is calculated based on the current detected by the current detection means. Power conversion equipment.

2. The voltage application means is It is composed of multiple switching elements, The control device includes: sequentially controlling the switching elements so that the motor in the measurement delta connection state is in a first connection state in which a current flows between first phases, a second connection state in which a current flows between second phases, and a third connection state in which a current flows between third phases; Calculating the leakage inductance based on a first current or a second current which is a current flowing through the motor in the first connection state or the second connection state, respectively, and a third current which is a current flowing through the motor in the third connection state. The power conversion device according to claim 1 .

3. The control device includes: The leakage inductance is calculated by subtracting the first inductance of the motor in the first connection state or the second inductance of the motor in the second connection state from the third inductance of the motor in the third connection state. The power conversion device according to claim 2 .

4. The voltage application means is The switching element is formed by connecting three series bodies in parallel, each of which has two switching elements connected in series. The power conversion device according to claim 2 or 3.

5. When the motor is a three-phase motor capable of switching a winding connection state between a Y connection and a Δ connection, a connection switching device is further provided for switching the connection state of the motor, The control device includes: When calculating the leakage inductance, the connection switching device is controlled so that the connection state of the motor is switched from the Δ connection to the measurement Δ connection. The power conversion device according to any one of claims 1 to 3.

6. The power conversion device according to any one of claims 1 to 3 is provided. Refrigeration cycle equipment.

7. A leakage inductance calculation method for calculating a leakage inductance of a three-phase electric motor, comprising the steps of: The leakage inductance of the motor is calculated based on the current flowing through the motor to which an AC voltage is applied, in a state in which the windings of the motor are connected in a V-shaped measurement delta connection in which one connection portion of the delta connection is removed. How to calculate leakage inductance.

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