JP7592198B2 - Electric motor drive device and air conditioner - Google Patents

Description

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

Conventionally, there is known an electric motor drive device that can switch the connection state of the motor windings between Y connection and Δ connection. In particular, in an electric motor using a permanent magnet, the magnets are demagnetized when the winding current, which is the current flowing through the windings, exceeds a predetermined allowable value, so an electric motor drive device with a protection function is used that prevents the magnets from being demagnetized by suppressing the winding current to below the allowable value. The electric motor drive device with a protection function detects the current flowing through the inverter and stops the inverter if the detected current exceeds a threshold value.

When detecting the current flowing through the inverter and comparing it with a threshold, the ratio of the detected current to the winding current varies depending on the wiring state, so a different threshold must be used depending on the wiring state. In a Y-connection, the current output from the inverter and the winding current are the same in magnitude, but in a Delta connection, the current output from the inverter is √3 times the winding current. Therefore, when controlling the inverter so that the current flowing through the inverter does not exceed a threshold in order to prevent demagnetization, the threshold used in the Y-connection must be 1/√3 times the threshold used in the Delta connection.

Patent document 1 discloses a control device for a synchronous motor that, when the stator winding of the motor is Y-connected, changes an overcurrent detection signal from low level to high level when the current value signal exceeds a threshold value defined for Y-connection, and, when the stator winding of the motor is Delta-connected, changes the overcurrent detection signal from low level to high level when the current value signal exceeds a threshold value defined for Delta connection.

International Publication No. 2019/082272

However, the control device for a synchronous motor disclosed in Patent Document 1 has a problem that when the connection state is Y-connection and the standard for detecting overcurrent is changed to the threshold value for the Δ connection due to a connection switching transition or a failure in the switching circuit, the overcurrent cannot be detected because the threshold value for the Δ connection is higher than the threshold value for determining an overcurrent in the Y connection, and demagnetization of the motor occurs.

The present disclosure has been made in consideration of the above, and aims to provide an electric motor drive device that can provide overcurrent protection to prevent demagnetization in an electric motor in which the winding connection state of the electric motor can be switched between Y connection and Δ connection.

In order to solve the above-mentioned problems and achieve the objective, the electric motor drive device of the present disclosure includes a connection determination control unit that outputs a connection switching signal indicating which of a plurality of connection states the windings of the stator of the electric motor should be switched to, a connection switching unit that switches the connection state based on the connection switching signal, and an overcurrent protection circuit that prevents a current above an overcurrent threshold from flowing through the electric motor. The connection determination control unit includes a rotor flux estimation unit that estimates the rotor magnetic flux of the electric motor, a connection switching control unit that generates an overcurrent threshold switching signal and a connection switching signal that switch the overcurrent threshold, and a determination processing unit that identifies an actual connection state using the rotor magnetic flux estimation result by the rotor magnetic flux estimation unit and determines whether the connection state indicated by the connection switching signal matches the actual connection state, and if the connection state indicated by the connection switching signal is a connection state in which the overcurrent threshold is higher than before switching, the connection determination control unit outputs an overcurrent threshold switching signal to the overcurrent protection circuit when the connection state indicated by the connection switching signal matches the actual connection state.

The electric motor drive device disclosed herein has the effect of providing overcurrent protection to prevent demagnetization in an electric motor in which the winding connection state of the motor can be switched between Y connection and Delta connection.

FIG. 1 is a diagram showing a configuration of an electric motor drive device according to a first embodiment; FIG. 1 is a diagram showing a configuration of a connection determination control unit of an electric motor driving device according to a first embodiment; FIG. 1 is a diagram showing an example of a hardware configuration for implementing a control circuit unit of an electric motor drive device according to a first embodiment; 1 is a flowchart showing an operation procedure of the electric motor drive device according to the first embodiment. FIG. 13 is a diagram showing the configuration of an air conditioner according to a second embodiment.

Below, the electric motor drive device and air conditioner relating to the embodiment are described in detail with reference to the drawings.

Embodiment 1.
FIG. 1 is a diagram showing a configuration of an electric motor drive device according to a first embodiment. The electric motor drive device 100 drives an electric motor 2. As shown in FIG. 1, the electric motor 2 is a three-phase type and has a plurality of windings. The electric motor drive device 100 includes a converter 10 that converts an AC voltage supplied from an AC power source 1 into a DC voltage, an inverter 20 that converts the DC voltage into an AC voltage and supplies the AC voltage to the electric motor 2, a current detection unit 21 that detects a current value of a current supplied from the inverter 20 to the electric motor 2, a connection switching unit 22 that switches a connection state of the electric motor 2, and a control circuit unit 23 that issues a command to the inverter 20 to drive the electric motor 2 based on the detected current value and issues a connection switching signal to the connection switching unit 22. The connection switching signal is a signal that indicates which of a plurality of connection states the windings of the stator of the electric motor 2 should be switched to.

The motor drive device 100 may be configured to obtain the current value of the current supplied from the inverter 20 to the motor 2 by detecting the current flowing between the converter 10 and the inverter 20 using a current detection resistor 11 instead of the current detection unit 21. The converter 10 may be configured to rectify with a diode bridge, or may be configured to step up and step down the voltage of the DC current using a known chopper.

The control circuit section 23 includes an overcurrent protection circuit 40 that detects an overcurrent from the current value of the current detection resistor 11, and a control microcontroller 50 that controls commands and connection switching signals for driving the electric motor 2. The control microcontroller 50 has a connection determination control section 30 that determines the rotor magnetic flux of the electric motor 2 based on voltage information such as the command value of the voltage applied by the inverter 20 to the electric motor 2 and the detected current value, and determines the connection state based on the estimated rotor magnetic flux.

The wiring switching unit 22 has three relays when the electric motor 2 is a three-phase type, and switches the three relays according to the wiring switching signal provided by the control microcontroller 50.

The overcurrent protection circuit 40 changes the overcurrent threshold based on instructions from the control microcontroller 50.

The electric motor 2 is capable of switching the winding connection state, and the connection switching unit 22 switches each relay to switch the connection state from Y connection to Δ connection, or from Δ connection to Y connection. When the common contact of each relay is connected to the b contact, the connection state is Y connection. On the other hand, when the common contact of each relay is connected to the a contact, the connection state is Δ connection.

The rotor magnetic flux when the connection state is Y-connection and the rotor magnetic flux when the connection state is Δ-connection have a √3:1 relationship. Note that the electric motor 2 is not limited to being able to switch the connection state between Y-connection and Δ-connection as long as it is capable of switching the connection state. The electric motor 2 may be capable of switching between three or more connection states. The connection states that the electric motor 2 can take are not limited to a specific connection state as long as the rotor magnetic flux can be changed by switching the connection state.

The inverter 20 has a plurality of switching elements. The switching elements are not shown in FIG. 1. The inverter 20 converts DC current into three-phase AC current by turning on and off each switching element in accordance with a PWM (Pulse Width Modulation) signal provided by the control microcontroller 50.

The current detection unit 21 detects the current value of two-phase AC current out of the three-phase AC current supplied from the inverter 20 to the electric motor 2. The current detection unit 21 outputs current information that is the detection result of the current value of the AC current. The current detection by the current detection unit 21 is not limited to the detection of two-phase AC current. The current detection unit 21 may detect the current of each phase of the three-phase AC current, or, as described above, may detect the combined current of the three-phase AC current flowing between the converter 10 and the inverter 20 by the current detection resistor 11.

Figure 2 is a diagram showing the configuration of the connection determination control unit of the electric motor drive device according to the first embodiment. In FIG. 2, the control circuit unit 23 is omitted from the illustration except for the connection determination control unit 30. The connection determination control unit 30 includes a rotor flux estimation unit 31, a connection switching control unit 34, a judgment value storage unit 35, a judgment processing unit 33, and a drive signal control unit 32. The rotor flux estimation unit 31 acquires current information input from the current detection unit 21, and calculates an estimated rotor flux, which is an estimated value of the rotor flux of the electric motor 2, based on voltage information such as a command value of the voltage applied to the electric motor 2 by the inverter 20 and current information. That is, the rotor flux estimation unit 31 estimates the rotor flux of the electric motor 2 based on voltage information indicating the voltage applied to the electric motor 2 and the detection value of the current flowing through the electric motor 2.

The wiring switching control unit 34 generates a wiring switching signal for controlling switching of the wiring state, and transmits the generated wiring switching signal to the wiring switching unit 22 and the judgment processing unit 33. The wiring switching control unit 34 also generates an overcurrent threshold switching signal for switching the overcurrent threshold, and outputs it to the overcurrent protection circuit 40. The judgment value memory unit 35 stores a wiring judgment threshold, which is a value used to judge the wiring state.

The judgment processing unit 33 acquires the estimated rotor flux from the rotor flux estimation unit 31 and judges the connection state based on the estimated rotor flux. The judgment processing unit 33 also receives the connection switching signal generated by the connection switching control unit 34. The judgment processing unit 33 reads the connection judgment threshold from the judgment value storage unit 35, identifies the actual connection state by comparing the rotor flux estimation result with the connection judgment threshold, and judges an abnormality in the connection state by comparing the actual connection state with the connection state indicated by the connection switching signal. An abnormality in the connection state refers to a difference between the actual connection state of the motor 2 and the connection state recognized by the motor drive device 100 for control of the motor 2. In this way, the judgment processing unit 33 identifies the actual connection state using the rotor flux estimation result by the rotor flux estimation unit 31, and judges whether the connection state indicated by the connection switching signal matches the actual connection state.

The above-mentioned connection determination threshold is set to a value between the values of the rotor magnetic flux in each connection state. In other words, the connection determination threshold is a value between the value of the rotor magnetic flux when the connection state is Y-connection and the value of the rotor magnetic flux when the connection state is Delta-connection. The connection determination threshold is determined in advance based on the specifications of the electric motor 2.

The overcurrent protection circuit 40 sets an overcurrent threshold for the Y connection and an overcurrent threshold for the Δ connection based on the judgment value stored in the judgment value memory unit 35. The overcurrent protection circuit 40 may set the overcurrent threshold by switching using hardware, or may set the overcurrent threshold by switching using software.

When the connection state is judged to be abnormal, the control circuit unit 23 allows the motor 2 to be deferred from stopping. The judgment processing unit 33 judges whether or not the motor 2 can be deferred from stopping. The judgment processing unit 33 counts the number of times the motor 2 has been deferred from stopping. If the number of times the motor 2 has been deferred from stopping has not reached a preset number, the judgment processing unit 33 judges that the motor 2 will be deferred from stopping. If the number of times the motor 2 has been deferred from stopping has reached a preset number, the judgment processing unit 33 judges that the motor 2 will not be deferred from stopping. If the motor 2 is not deferred from stopping, the drive signal control unit 32 stops generating the PWM signal based on the judgment result of the judgment processing unit 33 and stops the power supply from the inverter 20 to the motor 2. Information indicating the number of times preset as a criterion for judging whether or not the motor 2 can be deferred from stopping is called deferral number information. The deferral number information is stored in the judgment value storage unit 35.

3 is a diagram showing an example of a hardware configuration for realizing the control circuit unit of the electric motor drive device according to embodiment 1. The control circuit unit 23 is composed of a processing circuit 61 having a processor 63 and a memory 64, and hardware having an input unit 62 and an output unit 65.

A CPU (Central Processing Unit) can be applied to the processor 63. The processor 63 executes a control program. The control program is a program in which processes for realizing the functions of the rotor magnetic flux estimation unit 31, the connection switching control unit 34, the judgment processing unit 33, and the drive signal control unit 32 are described.

The memory 64 may be a non-volatile or volatile memory such as a random access memory (RAM), a read only memory (ROM), a flash memory, an erasable programmable read only memory (EPROM), or an electrically erasable programmable read only memory (EEPROM (registered trademark)). The memory 64 stores a control program. The memory 64 is also used as a temporary memory when the processor 63 executes various processes. The judgment value storage unit 35 is realized by a non-volatile memory.

The input unit 62 receives an input signal from the outside to the control circuit unit 23. For example, the input unit 62 receives current information. The output unit 65 outputs a signal generated by the control circuit unit 23 to the outside of the control circuit unit 23. For example, the output unit 65 outputs a PWM signal and a wiring switching signal.

The functions of the processing circuit 61 may be realized by dedicated hardware. For example, the processing circuit 61 may be realized by an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a circuit that combines these. A part of the control circuit unit 23 may be realized by the processor 63 and memory 64, and the remaining part may be realized by dedicated hardware.

Next, the calculation of the estimated rotor flux will be described. The estimated rotor flux is obtained in the process of estimating the rotational speed and rotational position of the electric motor 2 using a known adaptive observer. The rotor flux estimation unit 31 calculates the estimated rotor flux obtained in the process of estimating the rotational speed and rotational position of the electric motor 2. The rotor flux estimation unit 31 converts the current values of the three-phase AC current indicated in the current information into current values on the d-q axes, which are a rotating coordinate system.

It is known that, by using a method using an adaptive observer, it is possible to calculate an estimated magnetic flux vector and an estimated current vector from a state equation based on the voltage vector applied to the electric motor 2, the current vector output by the electric motor 2, and the estimated angular velocity.

The following equations (1) and (2) are the state equations of motor 2.

In formula (1) and formula (2), _Ld represents d-axis inductance, and _Lq represents q-axis inductance. In formula (1) and formula (2), R represents the resistance of the motor 2, ω represents the primary angular frequency, _ωr represents the angular velocity, _vds represents the d-axis voltage, _vqs represents the q-axis voltage, _ids represents the d-axis current, _iqs represents the q-axis current, _φds represents the d-axis stator flux, _φqs represents the q-axis stator flux, and _φdr represents the d-axis rotor flux. _h11 , _h12 , _h21 , _h22 , _h31 , and _h32 represent observer gains. Constants arbitrarily set according to the motor 2 are used for the observer gains. In formula (1) and formula (2), variables marked with the symbol "^" represent estimated values. The rotor magnetic flux is only in the d-axis direction, and the rotor magnetic flux in the q-axis direction is zero. For this reason, φ _qr , which is the q-axis rotor magnetic flux, is not included in equations (1) and (2).

In equation (1), the d-axis voltage v _ds and the q-axis voltage v _qs use the output voltage command value. The d-axis current i _ds and the q-axis current i _qs are calculated based on current information. The previous values in the control period are used for the estimated d-axis stator flux φ _ds ^, the estimated q-axis stator flux φ _qs ^, the estimated d-axis current i _ds ^, the estimated q-axis current i _qs ^, the primary angular frequency ω, and the estimated angular velocity ω _r ^. The integral value of the estimated d-axis stator flux φ _ds ^ and the integral value of the estimated q-axis stator flux φ _qs ^ are used for the estimated d-axis current i _ds ^ and the estimated q-axis current i _qs ^, respectively.

When the connection state of the motor 2 is switched, the magnetic flux of the motor 2 changes. At this time, the magnetic flux becomes the d-axis direction, that is, the polarity direction of the magnet. The rotor flux estimation unit 31 estimates the d-axis rotor magnetic flux φ _dr and detects the switching of the connection state by using the estimation result. From the relationship in equation (1), the estimated d-axis rotor magnetic flux φ _dr ^ can be calculated using the following equation (3).

The integral value of the calculation result by the formula (3) is the previous value in the control period. The estimated d-axis rotor magnetic flux φ _dr ^ is obtained by calculating (d/dt) φ _dr ^ taking the control period into consideration and adding the calculated result to the previous value, which is the integral value of the formula (3).

The determination processing unit 33 identifies the wiring state from the calculation result of the estimated rotor magnetic flux, utilizing the fact that the rotor magnetic flux changes depending on the wiring state. The determination processing unit 33 uses the wiring switching signal acquired from the wiring switching control unit 34 and a threshold value read from the determination value memory unit 35 to determine the wiring state. The determination processing unit 33 grasps the currently commanded wiring state based on the wiring switching signal. The determination processing unit 33 determines an abnormality in the wiring state by comparing the actual wiring state identified based on the estimation result of the estimated rotor magnetic flux with the wiring state indicated by the wiring switching signal.

Figure 4 is a flowchart showing the operation procedure of the electric motor drive device according to the first embodiment. In step S1, the judgment processing unit 33 judges whether or not there is a switch from Y connection to Δ connection. For example, the judgment processing unit 33 judges whether or not there is a switch from Y connection to Δ connection based on whether the connection switching signal is a signal indicating a switch to Y connection or a signal indicating a switch to Δ connection. At the time of step S1, the overcurrent threshold is normally a value corresponding to the connection before the switch.

When switching from a Δ connection to a Y connection, step S1 becomes No, and in step S4, the connection determination control unit 30 outputs a connection switching signal generated in the connection switching control unit 34 to switch from the Δ connection to the Y connection to the connection switching unit 22, changing the connection from the Δ connection to the Y connection. The connection determination control unit 30 also outputs an overcurrent threshold switching signal generated in the connection switching control unit 34 to the overcurrent protection circuit 40 to switch from the overcurrent threshold for the Δ connection to the overcurrent threshold for the Y connection, changing the overcurrent threshold to that for the Y connection.

When switching from a Δ connection to a Y connection, the overcurrent threshold is reduced, and since the overcurrent threshold does not become that for a Δ connection when the Y connection is in use, the process proceeds to step S10 after the connection switching signal and the overcurrent threshold switching signal are output. In step S10, the control circuit unit 23 continues to drive the electric motor 2.

When switching from a Y connection to a Δ connection, step S1 becomes Yes, and in step S2, the connection determination control unit 30 outputs a connection switching signal for switching from a Y connection to a Δ connection, generated in the connection switching control unit 34, to the connection switching unit 22, and changes the connection to a Δ connection. At the time of step S2, the overcurrent threshold remains the overcurrent threshold for the Y connection.

In step S3, the rotor flux estimation unit 31 calculates the estimated rotor flux. The rotor flux estimation unit 31 calculates the estimated rotor flux in the process of estimating the rotational speed and rotational position of the motor 2 by calculation using an adaptive observer.

In step S5, the judgment processing unit 33 judges whether the estimated rotor magnetic flux is greater than the connection judgment threshold. As described above, the connection judgment threshold is a value between the value of the rotor magnetic flux when the connection state is Y-connection and the value of the rotor magnetic flux when the connection state is Δ-connection. The judgment processing unit 33 judges whether the current actual connection state is Y-connection by comparing the estimated rotor magnetic flux with the connection judgment threshold.

If the estimated rotor magnetic flux is greater than the connection judgment threshold, the answer is Yes in step S5, and the judgment processing unit 33 judges that the current actual wiring state is Y connection. Since the currently commanded wiring state is a Δ connection, while the current wiring state is a Y connection, the currently commanded wiring state and the current actual wiring state do not match. For this reason, the judgment processing unit 33 judges that the wiring state is abnormal. If the current actual wiring state is judged to be a Y connection, the process proceeds to step S6.

If the estimated rotor magnetic flux is equal to or less than the connection judgment threshold, step S5 becomes No, and the judgment processing unit 33 judges that the current actual connection state is a delta connection. Since the currently commanded connection state and the current actual connection state are both delta connection, the judgment processing unit 33 judges that the connection state is normal. If the current actual connection state is judged to be a delta connection, the process proceeds to step S7.

In step S6, the judgment processing unit 33 judges whether the number of stop grace periods for the electric motor 2 has reached a preset number. If the number of stop grace periods for the electric motor 2 has reached a preset number, the answer is Yes in step S6 and the process proceeds to step S8. On the other hand, if the number of stop grace periods for the electric motor 2 has not reached the preset number, the answer is No in step S6 and the process proceeds to step S9.

In step S8, the drive signal control unit 32 outputs a drive signal to stop the electric motor 2, thereby stopping the electric motor 2. After step S8, the judgment processing unit 33 ends the processing.

In step S9, the judgment processing unit 33 increments the stop grace period count of the electric motor 2 by 1 and updates the grace period count information stored in the judgment value storage unit 35. After step S9, the process proceeds to step S3.

In step S7, the connection determination control unit 30 outputs an overcurrent threshold switching signal to the overcurrent protection circuit 40 to switch the overcurrent threshold for the Y connection generated in the connection switching control unit 34 to the overcurrent threshold for the Δ connection, thereby changing the overcurrent threshold for the Δ connection.

In step S10, the drive signal control unit 32 outputs a drive signal to the electric motor 2 to continue driving the electric motor 2.

The electric motor drive device 100 according to the first embodiment calculates an estimated rotor magnetic flux, and identifies the actual wiring state of the electric motor 2 based on the estimated rotor magnetic flux, thereby changing the overcurrent threshold based on the actual wiring state confirmed during the operation of the electric motor 2. For example, if the wiring state indicated by the wiring switching signal is a wiring state in which the overcurrent threshold is larger than before the switching, the wiring determination control unit 30 outputs an overcurrent threshold switching signal to the overcurrent protection circuit 40 to change the overcurrent threshold from the overcurrent threshold corresponding to the wiring state before the switching to the overcurrent threshold corresponding to the wiring state after the switching, when the wiring state indicated by the wiring switching signal matches the actual wiring state. Therefore, in the electric motor drive device 100, when the wiring state is switched to a wiring state in which the overcurrent threshold is larger than before the switching during normal operation, the electric motor 2 is not driven in a state in which the actual wiring state and the set overcurrent threshold are different.

The electric motor drive device 100 can avoid erroneous detection of an overcurrent by driving the electric motor 2 in a state where the actual wiring state does not match the set value of the overcurrent threshold. For example, even if the actual wiring state during normal operation is a delta connection, the electric motor 2 is driven in a state where the overcurrent threshold is for a Y connection, thereby avoiding erroneous detection of an overcurrent.

Furthermore, if the overcurrent protection circuit 40 switches the overcurrent threshold normally but the wiring state is abnormal, demagnetization may occur when the current flowing through the motor 2 increases. In particular, when switching from Y-connection to Δ-connection, if the wiring state does not switch to the Y-connection even though the overcurrent protection circuit 40 switches from the overcurrent threshold for Y-connection to the overcurrent threshold for Δ-connection, the motor 2 will be driven with the overcurrent threshold set too high. Therefore, by stopping the motor 2 when there is an abnormality in the wiring state, the motor 2 can be protected. This makes it possible to extend the life of the motor 2 and improve its reliability.

The electric motor drive device 100 calculates the estimated rotor magnetic flux in the process of estimating the rotational speed and rotational position of the electric motor 2 using an adaptive observer. This allows the electric motor drive device 100 to check the connection state through simple processing. This allows the electric motor drive device 100 to reduce the processing burden while the electric motor 2 is in operation. The electric motor drive device 100 can also reduce situations where processing cannot keep up with the control period. This allows the electric motor drive device 100 to stably control the electric motor 2 and achieve high reliability.

The electric motor drive device 100 identifies the actual connection state based on the rotor magnetic flux estimation result. The electric motor drive device 100 can identify the connection state by simply comparing the rotor magnetic flux with a connection determination threshold without using parameters such as the rotation speed or the load of the electric motor 2. This allows the electric motor drive device 100 to reduce the number of parameters used to identify the connection state. Furthermore, the electric motor drive device 100 can simplify the conditions used to identify the connection state. This allows the electric motor drive device 100 to reduce the processing load and stably control the electric motor 2.

Embodiment 2.
FIG. 5 is a diagram showing the configuration of an air conditioner according to the second embodiment. As shown in FIG. 5, the air conditioner 200 according to the second embodiment includes the motor drive device 100 and the motor 2 according to the first embodiment. That is, the air conditioner 200 is supplied with AC power from an AC power source 1. The air conditioner 200 includes a compressor 71 incorporating a compression mechanism 77 and the motor 2, a four-way valve 72, an outdoor heat exchanger 73, an expansion valve 74, an indoor heat exchanger 75, and a refrigerant pipe 76. The air conditioner 200 is not limited to a separate type air conditioner in which the outdoor unit is separated from the indoor unit, and may be an integrated type air conditioner in which the compressor 71, the indoor heat exchanger 75, and the outdoor heat exchanger 73 are provided in one housing. The motor 2 is driven by the motor drive device 100.

Inside the compressor 71, there is provided a compression mechanism 77 that compresses the refrigerant, and an electric motor 2 that operates the compression mechanism 77. The refrigerant circulates through the compressor 71, the four-way valve 72, the outdoor heat exchanger 73, the expansion valve 74, the indoor heat exchanger 75, and the refrigerant piping 76 to form a refrigeration cycle. Note that, although the air conditioner 200 has been given as an example of a refrigeration cycle device equipped with the electric motor drive device 100 and the electric motor 2 according to the first embodiment, the refrigeration cycle device equipped with the electric motor drive device 100 and the electric motor 2 according to the first embodiment is not limited to the air conditioner 200, and may also be applied to a refrigerator or a heat pump hot water supply device.

In addition, in the above-mentioned second embodiment, an example configuration has been described in which the electric motor 2 is used as the driving source for the compressor 71, and the electric motor 2 is driven by the electric motor drive device 100. However, the electric motor 2 may be applied as a driving source for driving an indoor unit blower and an outdoor unit blower (not shown) provided in the air conditioner 200, and the electric motor 2 may be driven by the electric motor drive device 100. The electric motor 2 may also be applied as a driving source for the indoor unit blower, the outdoor unit blower, and the compressor 71, and the electric motor 2 may be driven by the electric motor drive device 100.

As described above, the air conditioner 200 of this embodiment can prevent the overcurrent threshold for the Δ connection from being applied in the Y connection state by using the motor drive device 100 of embodiment 1. Furthermore, if the identified connection state and the overcurrent threshold do not match, the motor 2 is stopped, and the operation of the air conditioner 200 can be stopped. Therefore, it is possible to prevent the boost operation from continuing in a phase loss state, and to prevent the phenomenon in which the air conditioner 200 cannot be operated continuously. This makes it possible to maintain comfort and energy saving. Even when the motor drive device 100 of embodiment 1 is applied to a refrigeration cycle device other than the air conditioner 200, the same effect as the air conditioner 200 can be achieved.

The configurations shown in the above embodiments are merely examples of the content, and may be combined with other known technologies, and parts of the configurations may be omitted or modified without departing from the gist of the invention.

1 AC power source, 2 electric motor, 10 converter, 11 current detection resistor, 20 inverter, 21 current detection section, 22 connection switching section, 23 control circuit section, 30 connection determination control section, 31 rotor magnetic flux estimation section, 32 drive signal control section, 33 determination processing section, 34 connection switching control section, 35 determination value storage section, 40 overcurrent protection circuit, 50 control microcontroller, 61 processing circuit, 62 input section, 63 processor, 64 memory, 65 output section, 71 compressor, 72 four-way valve, 73 outdoor heat exchanger, 74 expansion valve, 75 indoor heat exchanger, 76 refrigerant piping, 77 compression mechanism, 100 electric motor drive device, 200 air conditioner.

Claims (5)

a connection determination control unit that outputs a connection switching signal that indicates which of a plurality of connection states the windings of the stator of the electric motor should be switched to;
a connection switching unit that switches the connection state based on the connection switching signal;
an overcurrent protection circuit that prevents a current equal to or greater than an overcurrent threshold from flowing through the motor;
The connection determination control unit is
a rotor flux estimator that estimates a rotor flux of the electric motor;
a connection switching control unit that generates an overcurrent threshold switching signal for switching the overcurrent threshold and the connection switching signal;
a determination processing unit that identifies an actual connection state by using a result of the rotor magnetic flux estimation by the rotor magnetic flux estimation unit, and determines whether or not the connection state indicated by the connection switching signal matches the actual connection state,
The connection determination control unit, when the connection state indicated by the connection switching signal is a connection state in which the overcurrent threshold is higher than before switching, outputs the overcurrent threshold switching signal to the overcurrent protection circuit, when the connection state indicated by the connection switching signal matches the actual connection state, to change the overcurrent threshold from the overcurrent threshold corresponding to the connection state before switching to the overcurrent threshold corresponding to the connection state after switching, in the electric motor drive device. The electric motor drive device according to claim 1, wherein the judgment processing unit counts the number of times that the wiring state indicated by the wiring switching signal does not match the actual wiring state, and performs processing to stop the electric motor when the counted number reaches a preset number. an inverter for supplying a current to the electric motor;
a current detection unit that detects a value of a current supplied from the inverter to the electric motor,
The electric motor drive device according to claim 1 , wherein the rotor magnetic flux estimator estimates the rotor magnetic flux based on a detection result of the current detector. An electric motor drive device according to any one of claims 1 to 3, wherein the connection state is a Y connection or a Δ connection. An air conditioner comprising an electric motor drive device according to any one of claims 1 to 4.

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