JP2022064817A - Motor drive device and refrigerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor drive device capable of precisely calculating a state of a rotor without passing an excessive short circuit current, and a refrigerator employing the same.

SOLUTION: A motor drive device comprises: an inverter 2 to output, to a permanent magnet synchronous motor 3, an AC power converted from an input DC power; and a control unit 5 to control operation of the inverter 2. When the permanent magnet synchronous motor 3 is in a free-run state, the control unit 5 calculates a state of a rotor of the permanent magnet synchronous motor 3 in the free-run state on the basis of a motor current of the permanent magnet synchronous motor 3 detected by turning on PWM control performed by the inverter 2, and controls the inverter 2 such that the permanent magnet synchronous motor 3 starts rotation from the free-run state on the basis of the calculated state of the rotor.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2022,JPO&INPIT

Description

The present invention relates to a motor drive device provided with means for restarting a motor from a state in which it is idling, and a refrigerating device using the motor drive device.

Motor drive systems consisting of an inverter that converts direct current to alternating current and a permanent magnet synchronous motor are widely used in the fields of home appliances and industrial equipment. In particular, in fields such as refrigeration equipment, such motor drive systems are used to improve the efficiency of equipment.

Generally, in order to drive a permanent magnet synchronous motor with high efficiency, rotor position information of the motor is required. The rotor position of the motor can be directly detected using a position detector such as an encoder, but there are problems in cost and reliability. Therefore, in recent years, position sensorless control for detecting the rotor position of a permanent magnet synchronous motor without using a position detector has been proposed and applied to various products.

One of the problems in the position sensorless control of the permanent magnet synchronous motor is a method of restarting the rotor from a state where it is idling (referred to as "free run start"). For example, a drive motor such as a fan may have already rotated before starting due to the inertia of the load or an external force (outside wind). If there is no information such as the rotor position, rotation speed and rotation direction in the idling state, it is necessary to wait until the motor stops or forcibly apply brake control to stop the rotation and then restart from the stopped state. Therefore, it takes a long time to restart.

On the other hand, Patent Document 1 is a technique for instantaneously short-circuiting the windings of a motor by an inverter using an induced voltage generated when the motor idles, and calculating the position of a rotor based on the current flowing at this time. And patent document 2.

In the technique described in Patent Document 1, three lower arm elements among the switching elements constituting the motor drive inverter are turned on at the same time, a short-circuit current is passed through the motor winding, and three-phase motor current detection information is obtained. The position and rotation speed of the rotor are calculated based on.

In the technique described in Patent Document 2, elements of different arms for two phases of a motor driving inverter are simultaneously turned on and off, and the bus current on the DC side of the inverter is detected to determine the rotor position of the motor. Calculate the rotation speed.

Japanese Patent No. 4103051 Japanese Unexamined Patent Publication No. 2018-170928

In the technique described in Patent Document 1, in order to detect the short-circuit current of the motor winding, it is necessary to detect the motor current for at least two phases by using a current sensor, which requires a circuit cost.

In the technique described in Patent Document 2, the detection of the current flowing through the bus resistance eliminates the need for a current sensor for detecting each phase current, but since a special PWM control mode and current detection processing are used, the motor is used. The calculation for calculating the rotor position and rotation speed of the is complicated, and an error is likely to occur in the estimation result.

Therefore, the present invention can support a detection method for the current flowing through a bus resistor, and can calculate the position and speed of the motor rotor with high accuracy without using a special PWM control mode or current detection processing. The device and the refrigerating equipment using the device are provided.

In order to solve the above problems, the motor drive device according to the present invention is
It is equipped with an inverter that outputs AC power converted from the input DC power to a permanent magnet synchronous motor, and a control unit that controls the operation of the inverter.
The control unit
When the permanent magnet synchronous motor is in the idling state, the permanent magnet synchronous motor in the idling state is based on the motor current of the permanent magnet synchronous motor detected by turning on the PWM control by the inverter. Calculate the state of the rotor and
It is characterized in that the inverter is controlled so that the permanent magnet synchronous motor starts rotation from the idling state based on the calculated state of the rotor.

According to the present invention, the circuit cost, the board area, and the number of A / D ports used by the microcomputer can be reduced by eliminating the need for a sensor for detecting the rotation phase of the idling motor, an induced voltage detection circuit, and the like. Further, the state of the rotor can be calculated with high accuracy without passing an excessive motor current during the period for calculating the rotor position and the rotation speed. Therefore, the reliability of the start control of the motor drive device and the refrigeration equipment using the motor drive device is improved.

Issues, configurations and effects other than those described above will be clarified by the description of the following embodiments.

It is an overall block diagram of the motor drive device which is Embodiment 1 of this invention. It is a block diagram which shows the control composition of a control part. It is a block diagram of phase and velocity calculation. It is a time waveform diagram of a PWM signal and a shunt resistance current at the time of phase and speed calculation. It is a state transition diagram which shows the transition of the operating state of a motor drive device at the time of idling. It is a schematic waveform diagram which shows the current command value and the rotation speed command value at the time of motor start. It is a schematic waveform diagram which shows the current command value and the rotation speed command value at the time of motor start. It is a block diagram of the refrigerating apparatus which is Example 2 of this invention.

Hereinafter, examples of the present invention will be described with reference to the drawings.

<Device configuration>
FIG. 1 is an overall configuration diagram of a motor drive device according to a first embodiment of the present invention. The motor drive device shown in FIG. 1 is driven by a DC power supply 1, an inverter 2 that converts DC power from the DC power supply 1 into AC power, a permanent magnet synchronous motor 3 to be driven, and a permanent magnet synchronous motor 3. It includes a mechanical motor load 4, a control unit 5 that controls the inverter 2, and an amplifier 7 that amplifies the signals of the shunt resistance 6 and the shunt resistance 6 between the DC power supply 1 and the inverter 2. In this embodiment, the motor load 4 is a fan for refrigerating equipment.

As the DC power supply 1, a power conversion device (for example, a diode rectifier, a regulated power supply, etc.) or a battery that converts AC power received from an AC power source such as a commercial AC power supply (not shown) into DC power is applied.

In the inverter 2, two arm circuits in which a semiconductor switching element (in this embodiment, an IGBT (Insulated Gate Bipolar Transistor)) and a diode are connected in antiparallel, that is, a series connection circuit in which an upper arm and a lower arm are connected in series. Is connected between the pair of positive and negative terminals of the DC power supply 1. Since the inverter 2 is a three-phase inverter, it is provided with three such series connection circuits for the number of AC phases, that is, three. Here, the upper arm and the lower arm are connected to the high potential side and the low potential side of the DC power supply 1, respectively. The series connection points of the upper and lower arms are connected to the AC terminal, and the permanent magnet synchronous motor 3 is connected to the AC terminal.

The bus on the low potential side of the inverter 2 is connected to the negative terminal of the DC power supply 1 via the shunt resistor 6 for current detection. The current detection signal detected by the shunt resistor 6 is input to the control unit 5 via the amplifier 7. Here, instead of the shunt resistor 6, another current detection means such as a current sensor may be used. The output signal of the amplifier 7 is converted into a digital signal by the sampling and hold circuit, the A / D converter, and the like for the digital calculation in the control unit 5.

As the control unit 5, a semiconductor arithmetic unit such as a microcomputer or a DSP (digital signal processor) is used.

In this embodiment, as will be described later, the control unit 5 detects and synchronizes the rotor position of the permanent magnet synchronization motor without using a position detector, and executes position sensorless control. Therefore, the permanent magnet is used. The synchronous motor 3 is not provided with a magnetic pole position detecting means such as a Hall element for detecting the position of the rotor or the rotating shaft.

<Explanation of overall control>
FIG. 2 is a block diagram showing a control configuration of the control unit 5 in the first embodiment. The control unit 5 has each function indicated by each block by executing a predetermined program by the semiconductor arithmetic unit.

The control unit 5 calculates a voltage command signal applied to the motor by dq-axis vector control, and generates a PWM (Pulse Width Modulation) control signal of the inverter. The control unit 5 includes a speed controller 10, a d-axis current command generator 11, a voltage controller 12, a 2-axis / 3-phase converter 13, a speed and phase estimator 14, and 3-phase / 2-axis conversion. It includes a device 15, a current reproduction calculator 16, an idling state calculator 17, a voltage command switch 18, and a PWM controller 19. The functions related to the start control at the time of idling will be described later.

The current reproduction calculator 16 uses the current detection signal (i _sh ) output from the amplifier 7 and the three-phase voltage command (v _u ^* , v _v ^* , v _w ^* ) to generate the three-phase motor current from the inverter 2. Reproduce (i _u , i _v , i _w ). Since a method for reproducing a three-phase motor current from a current signal of a shunt resistor is known, detailed description thereof will be omitted here. In addition, in FIG. 1, in order to reduce the cost, a method of reproducing the three-phase current from the current detection signal ( _ish ) detected by the shunt resistor 6 is adopted, but the embodiment is not particularly limited. .. Therefore, instead of the shunt resistance 6, an AC current which is an output of the inverter circuit 2 may be detected by using a current detecting means such as a current sensor. In this case, the three-phase current detected by the current detecting means is 3 It may be input to the phase / 2-axis converter 15.

The 3-phase / 2-axis converter 15 has a dc-axis based on the reproduced three-phase output currents (i _u , _iv , i _w ) and the velocity and phase information θ _dc estimated by the phase estimator 14. The current (i _dc ) and the qc axis current (i _qc ) are calculated based on Equation 1 and Equation 2. Equation 1 represents a so-called three-phase / two-axis transformation, and Equation 2 represents a transformation to a rotating coordinate system.

The dc-qc axis is the estimation axis of the vector control system based on the estimated position information, and the d-q axis is the motor rotor axis. Here, the axis error between the dq axis and the dc-qc axis is defined as Δθc. ..

In FIG. 2, the speed controller 10 brings the deviation between the speed command value and the speed and the estimated speed estimated by the phase estimator 14 close to 0 based on the speed command value (ω ^* ) from the outside. That is, the qc axis current command value (i _qc ^* ) is created so that the estimated speed approaches the speed command value. Further, in order to minimize the motor current, the current command generator 11 generates a _dc -axis current command value (idc ^* ).

The voltage controller 12 in FIG. 2 has a dc-axis current command value i _dc ^* given by the current command generator 11, a qc-axis current command value i _qc ^* given by the speed controller 10, and a three-phase / two-axis conversion. Using the dc-axis current detection value i _dc and qc-axis current detection value i _qc given by the device 15, the dc-axis voltage command value v _dc ^* and the qc-axis voltage command value v _qc using the speed command value ω ^* and the motor constant. ^* Is calculated and output.

The 2-axis / 3-phase converter 13 outputs the voltage command (v _dc ^* , v _qc ^* ) of the dc-qc axis calculated by the voltage controller 12 and the phase information (θ _dc ) from the speed and phase estimator 14. Using, the three-phase voltage command (v _u ^* , v _v ^* , v _w ^* ) is calculated and output based on the formulas 3 and 4. The mathematical formula 3 represents a conversion from a rotating coordinate system to a fixed coordinate system. Further, the mathematical formula 4 represents a so-called two-axis / three-phase transformation.

The speed and phase estimator 14 uses the dc-axis current detection value (i _dc ) and the qc-axis current detection value (i _qc ) and the dc-qc-axis voltage command (v _dc ^* , v _qc ^* ). Then, the position and rotation speed of the rotor are estimated and output as phase information (θ _dc ) and estimated speed (ω).

As a result, in the first embodiment, position sensorless control becomes possible, and the cost of the entire drive system can be reduced. Since the specific estimation means in the velocity and phase estimator 14 is known, detailed description thereof will be omitted here.

<Explanation of phase detection during idling>
When the permanent magnet synchronous motor 3 restarts from the idling state, depending on the rotational speed of the permanent magnet synchronous motor 3, it becomes difficult to start the motor by the control shown in FIG. 2 unless the rotor position and the rotational speed information are acquired. ..

On the other hand, the first embodiment includes means for calculating the rotor position and the rotation speed in the idle state of the permanent magnet synchronous motor 3. The means thereof will be described below.

When the permanent magnet synchronous motor 3 idles, an induced voltage is generated from the winding. The induced voltage is applied to the U-phase, V-phase, and W-phase AC terminals that are the connection between the permanent magnet synchronous motor 3 and the inverter. If the reference of the electric phase (θ _d ) of the permanent magnet synchronous motor 3 is the U-phase winding position and the neutral point of the three-phase winding of the permanent magnet synchronous motor 3 is the reference potential, the U-phase and V-phase are used. The phase-induced voltage (eu, _ev , e _w ) of the _W phase is expressed by Equation 5. In Equation 5, ω is the motor speed, and Ke is the motor-induced voltage constant.

FIG. 3 is a configuration diagram of an idling state calculator 17 that calculates the rotor position and the rotational speed of the permanent magnet synchronous motor in the idling state. The idling state calculator 17 includes an on / off signal generator 20, a current phase calculator 21, a speed calculator 22, a motor phase calculator 23, and a voltage command generator 24.

The on / off signal generator 20 generates a control signal for controlling the presence / absence of a PWM signal, and turns the PWM operation of the inverter on (hereinafter referred to as “on state section”) and off state (hereinafter referred to as “on state section”). Hereinafter referred to as "off state section") is set. In the ON state of the PWM operation, all the constituent elements of the inverter perform an on / off switching operation according to the PWM signal, and the voltage command value from the voltage command generator 24 is transmitted to the inverter 2 through the voltage command switch 18. Outputs the voltage (v _u , v _v , v _w ) from. In this state, the voltage difference between the output voltage of the inverter 2 and the induced voltage of each phase is applied to each stator winding of the permanent magnet synchronous motor 3. At this time, since there is a winding inductance (L) and a winding resistance (R), the motor current increases from 0. Here, since the influence of the winding resistance is generally sufficiently smaller than the inductance, if the influence is ignored, the motor current, the output voltage of the inverter 2 (v _u , v _v , v _w ) and the induced voltage are according to Equation 6. The relationship of ( _eu , e _v , e _w ) is expressed.

As described above, if the initial motor current is 0, the output voltage (v _u , v _v , v _w ) and induced voltage (v u, v v, v w) of the inverter 2 and the induced voltage (v u, v v, v w) during the on-state section (t_on) of the PWM operation of the inverter 2 Assuming that e _u , e _v , e _w ) is almost constant, the motor current (i _u , _iv , i _w ) at the end of the on-state section of the PWM operation is expressed by Equation 7.

According to the equation 7, the motor current (i _u , _iv , i _w ) at the end of the on state of the PWM operation is proportional to the time width (t _{_on} ) of the on section.

<PWM on / off operation and on state section adjustment>
Further, as described above, since the motor current in the ON state of the PWM operation is related to the induced voltage, the induced voltage becomes high when the idling speed is high, so that an excessive motor current is generated and semiconductor switching is performed. The element or diode may be destroyed. On the other hand, when the idling speed is low, the induced voltage is low, so that the motor current is also small, and it becomes difficult to detect the motor current with sufficient accuracy.

Therefore, in the first embodiment, the on / off signal generator 20 corresponds to a wide range of idling speeds by adjusting the on-state section (t _{_on} ) of the PWM operation of the inverter 2. Specifically, the three-phase motor current is reproduced by using the current reproduction calculator 16 in the on-state section of the PWM operation. The on / off signal generator 20 adjusts the time width of the on-state section of the PWM operation by using the reproduced value of the three-phase current. As an example, the on / off signal is controlled by comparing the motor current reproduced from the current reproduction calculator 16 with a preset current level value. The current level value here is preferably in the range of about 20% or more and 80% or less of the rated current in order to reduce the detection error of the current detection value and the influence of noise. When the current detection value in the on section of the PWM operation exceeds the current level value, all the PWM signals are turned off and the operation shifts to the off state section.

In the OFF state section of the PWM operation, the motor current returns to the DC power supply through the diode connected in antiparallel to the semiconductor switching element that is turned off. At this time, since the DC power supply voltage is also applied to each stator winding, the motor current is attenuated to 0. Further, the width of the OFF state section of the PWM operation is set so that the motor current returns to 0 each time. After the on-state section has elapsed, the PWM operation shifts to the on-state section again, and the motor current is generated from 0 again. By providing the OFF state section in the PWM operation in this way, overcurrent can be prevented.

FIG. 4 is a time waveform diagram of the PWM signals (30, 31, 32) and the shunt resistance current waveform (33) of the lower arm of each phase of the on state section and the off state section of the PWM operation. The PWM signal of the upper arm element of each phase not shown in FIG. 4 is a reverse phase signal of the corresponding lower arm PWM signal (30, 31, 32) in the on state section of the PWM operation, and is an off state of the PWM operation. In the section, it is the same off signal as the lower arm. Further, as shown in the time enlarged view at the lower part of FIG. 4, in the on-state section of the PWM operation, the PWM signal of the three-phase changes in the level of the PWM signal in order to shift the rising and falling timings of each phase. A shunt resistance current waveform (33) is generated near the time point (conversion from high level to low level or from low level to high level).

<Phase calculation from current>
In the current phase calculator 21, when the on / off signal from the on / off signal generator 20 changes from on to off, the equation 8 is calculated from the final reproduction value (i _u , _iv , i _w ) of the three-phase motor current. Use to calculate the current phase (θi).

<Speed calculation from phase difference>
Further, after the second and subsequent current phase (θi) calculations, as shown in Equation 9, the initial rotation speed (ω ₀ ) is calculated by the speed calculator 22 from the difference between the calculation results of the previous and next current phases and the time difference (Δt). Calculate.

Further, the rotation direction of the motor is determined from the positive and negative of the rotation speed, and the initial phase θdc of the motor rotor is calculated by the motor phase calculator 23 using the equation 10.

Further, in order to improve the calculation accuracy of the rotation speed, various statistical processes such as averaging the calculation results of a plurality of times may be performed.

The initial rotation speed from the speed calculator 22 and the motor phase calculator 23 and the initial phase of the motor rotor are set to the initial values of the speed & phase estimator 14 shown in FIG. 2, and the control of FIG. 2 is activated.

Further, the voltage command generator generates a three-phase voltage command value in the on-state section. Theoretically, any value within the range in which the three-phase voltage command can be output by the inverter may be used. Generally, for convenience of arithmetic processing, the three-phase voltage command may be set to 0 or the same value. However, in order to reproduce the three-phase current from the shunt current, processing such as adding and subtracting the shift amount to the uphill and downhill of the carrier wave of the triangular wave is performed to the three-phase voltage command value. Since the technique of reproducing the three-phase current from the shunt current is known, detailed description thereof is omitted here.

<Startup sequence>
FIG. 5 is a state transition diagram showing a transition of the operating state of the motor drive device when the permanent magnet synchronous motor 3 is restarted at the time of idling.

In the idling state, rotor information (rotor phase, rotation speed and rotation direction) is calculated as described above, and the operating state transitions according to the calculated rotation speed ω. When the rotor is reversed, for example, if the magnitude of the rotation speed exceeds the preset position sensorless minimum speed value, the calculated rotor phase and speed are set to the initial values of the speed and phase estimator 14. After setting, the control in FIG. 2 is activated, and the reverse rotation position sensorless operation mode, the reverse rotation synchronous operation mode, the normal rotation synchronous operation mode, and the normal rotation position sensorless operation mode are sequentially performed as shown by the arrows in the figure. , The operating state changes.

For example, if it is calculated that the motor in the idling state is rotating in the reverse direction at a rotation speed ω equal to or higher than the first threshold value ω _th1 , the mode is changed to the reverse position sensorless operation mode, and then the other operation modes are sequentially changed. Transition.

Further, when it is calculated that the motor in the idling state is rotating in the reverse direction at a rotation speed ω larger than the second threshold value _ωth2 and smaller than the first threshold value ωth1, the mode is changed to the reverse synchronous operation mode. Then, the operation mode is sequentially changed to another operation mode.

Further, when it is calculated that the motor in the idling state is rotating forward at a rotation speed ω larger than the second threshold value _ωth2 and smaller than the first threshold value ωth1, the normal rotation synchronous operation mode is set. It transitions and then sequentially transitions to another operation mode.

Further, when it is calculated that the motor in the idling state is rotating in the normal direction at a rotation speed ω equal to or higher than the first threshold value ω _th1 , the mode shifts to the normal rotation position sensorless operation mode. FIG. 6 is a schematic waveform diagram showing a current command value and a rotation speed command value at the time of starting the motor corresponding to the case where the rotation speed calculated during the normal rotation of the motor exceeds the position sensorless minimum speed value. When the rotation speed in the idling state exceeds the position sensorless minimum speed value, as shown in FIG. 6, the mode transitions from the idling state calculation mode to the normal rotation position sensorless operation mode. At this time, the dc-axis current command value I _dc ^* changes at 0, and when the normal rotation position sensorless operation mode is entered, the dc-axis current command value I _dc ^* is given, and the motor rotates at a predetermined rotation speed.

Further, when the calculated rotation speed is equal to or lower than the set minimum level (second threshold value ω _th2 ) (for example, when the rotation speed in the idling state is almost zero regardless of whether the rotation speed is normal or reverse), the operation is performed. The state first transitions to the positioning mode, and then transitions to the normal rotation synchronous operation mode and the normal rotation position sensorless operation mode in this order. FIG. 7 is a schematic waveform diagram showing the current command value and the rotation speed command value at the time of starting the motor in this case. As shown in FIG. 7, the operation modes include a positioning mode in which the rotor is fixed in a predetermined rotation position by gradually increasing the dc-axis current command value I _dc ^* flowing in the predetermined motor winding, and a predetermined mode. The synchronous operation mode that controls the applied voltage applied to the permanent magnet synchronous motor 3 according to the dc-axis current command value I _dc ^* and the rotation speed command value ω1 ^* , and the dc-axis current command value I _dc ^* are attenuated to 0. Three types of operation modes, a position sensorless mode for adjusting the qc axis current command value I _qc ^* and the inverter frequency so that the axis error Δθc becomes a predetermined value, are set and executed in this order.

As described above, according to the first embodiment, the on-state section and the off-state space of the PWM operation are provided at the time of phase detection during idling, and the on-state section is adjusted to have a sufficient size for current detection. The magnitude of the motor current can be suppressed while the motor current is flowing. Therefore, the rotational state of the rotor can be calculated with high accuracy without a sensor without passing an excessive current. Further, by controlling the inverter based on the calculated rotor state, the permanent magnet synchronous motor can efficiently start rotation from the idling state.

Further, in the first embodiment, only a small-scale function addition (program addition) is performed to add a PWM control signal generation and a rotor information estimation function for idling start control, which is a large circuit. No addition required. Therefore, the start-up performance can be improved without increasing the device size and cost.

FIG. 8 is a block diagram of a freezing device according to a second embodiment of the present invention. Here, the refrigerating equipment is a device that harmonizes the temperature, such as an air conditioner or a refrigerator. In the second embodiment, the fan motor is driven by the motor drive device according to the first embodiment described above.

As shown in FIG. 8, the refrigerating equipment 300 includes heat exchangers 301 and 302, fans 303 and 304 for blowing air to these heat exchangers, a fan motor 305 for driving the fan 304, and a refrigerant. A compressor 306 that compresses and circulates, a pipe 307 that is arranged between the heat exchanger 301 and the heat exchanger 302, and between the compressor 306 and the heat exchangers 301 and 302, through which the refrigerant flows, and a motor. It is composed of a drive device 308. A permanent magnet synchronous motor is used as the fan motor 305 that rotationally drives the fans 303 and 304. The motor drive device 308 includes a DC power supply circuit that converts AC power from a commercial AC power supply into DC power, and a motor drive inverter that converts DC power from this DC power supply circuit into AC power and supplies it to the fan motor 305. I have.

In the second embodiment, the fan motor driving inverter in the motor driving device 308 is controlled by the control unit 5 according to the first embodiment.

According to the second embodiment, even if the fan motor is idling due to an external wind or the like, the motor can be reliably restarted without providing a position sensor, so that the reliability of the refrigerating equipment is improved. The above-mentioned embodiment of the second embodiment is not limited to the application to the freezing equipment. Therefore, the second embodiment may be applied to an apparatus using a permanent magnet synchronous motor other than the refrigeration apparatus.

According to the embodiment of the present invention described above, it is possible to provide a motor drive device capable of calculating the state of the rotor with high accuracy without passing an excessive short-circuit current and a refrigerating device using the motor drive device.

Although the present invention has been described above with embodiments, the present invention is not limited to the above-described embodiments, and as long as the present invention exerts its actions and effects within the range of embodiments that can be inferred by those skilled in the art. , Is included in the scope of the present invention.

The present invention is not limited to the above-mentioned examples, and includes various modifications. For example, the above-mentioned examples have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations. Further, it is possible to add / delete / replace a part of the configuration of each embodiment with another configuration.

For example, the current detecting means may detect by a current transformer (CT) instead of the shunt resistor. In this case, the current detection point may be the inverter output unit. Further, the permanent magnet synchronous motor may be an embedded magnet type or a surface magnet type.

1 ... DC power supply,
2 ... Inverter,
3 ... Permanent magnet synchronous motor,
4 ... Motor load,
5 ... Control unit,
6 ... Shunt resistance,
7 ... Amplifier,
10 ... Speed controller,
11 ... d-axis current command generator,
12 ... Voltage controller,
13 ... 2-axis 3-phase converter,
14 ... Velocity and phase estimator,
15 ... 3-phase 2-axis converter,
16 ... Current reproduction calculator,
17 ... Idling state calculator,
18 ... Voltage command switch,
19 ... PWM controller,
20 ... On / off signal generator,
21 ... Current phase calculator,
22 ... Speed calculator,
23 ... Motor phase calculator,
24 ... Voltage command generator,
30 ... PWM signal of U-phase lower arm element,
31 ... PWM signal of V-phase lower arm element,
32 ... PWM signal of W phase lower arm element,
33 ... Shunt resistance current waveform,
40 ... dc-axis current command waveform,
41 ... QC axis current command waveform,
42 ... Rotation speed command waveform,
300 ... Refrigeration equipment,
301, 302 ... Heat exchanger,
303, 304 ... Fan,
305 ... Fan motor,
306 ... Compressor,
307 ... plumbing,
308 ... Motor drive device

Claims (5)

In a motor drive device including an inverter that outputs AC power converted from input DC power to a permanent magnet synchronous motor and a control unit that controls the operation of the inverter.
The control unit
When the permanent magnet synchronous motor is in the idling state, the permanent magnet synchronous motor is released from the idling state based on the motor current of the permanent magnet synchronous motor detected by turning on the PWM control by the inverter. Control the inverter to start rotation,
A motor drive device comprising switching the PWM control by the inverter to an off state when the value of the motor current exceeds a predetermined threshold value. The control unit
The motor drive device according to claim 1, wherein the motor current is controlled to be attenuated to 0 when the PWM control by the inverter is turned off. The control unit
The motor drive device according to claim 1 or 2, wherein the position of the rotor is calculated as the state of the rotor. The control unit
The motor drive device according to claim 3, wherein the rotation speed or the rotation direction of the rotor is calculated based on the difference in the positions of the rotors calculated at different time points. The heat exchanger, the compressor that compresses and circulates the refrigerant, the fan that blows air to the heat exchanger, the permanent magnet synchronous motor that drives the fan, and any one of claims 1 to 4. The motor drive device described, and the refrigeration equipment provided with.

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