JP6677067B2 - Motor drive - Google Patents

Description

  The present invention relates to a motor drive device, and more particularly to a configuration in which a regenerative power is consumed by short-circuiting a winding of a motor to apply a dynamic brake.

  2. Description of the Related Art Conventionally, in a motor drive device using an inverter, a configuration that brakes the rotation of the motor by consuming the regenerative power generated in the winding of the motor when the motor stops through the inverter is disclosed in many documents. Have been. (For example, see Patent Document 1).

  This drive device includes an inverter having three phases of arms each including a switching element for an upper arm and a switching element for a lower arm connected in a totem pole type, and one end of each of windings corresponding to the three phases. A three-phase motor that is connected in common and driven by an inverter is provided. When the rotation of the three-phase motor is stopped, all the switching elements of the upper arm or the lower arm are turned on to short-circuit the winding of the motor. Therefore, a dynamic brake is applied to the three-phase motor, and the rotation of the motor stops.

  By the way, in recent years, among such inverter functions, an intelligent power module in which the switching element peripheral circuits are integrated into one package is often used. This intelligent power module measures the switching element of the upper and lower arms, the driving circuit of the switching element, and the temperature of this switching element, and forcibly turns off the lower arm when this temperature exceeds an allowable value. A protection function is provided inside.

  On the other hand, the switching element of the upper arm is connected in series with the switching element of the lower arm. Therefore, when the switching element of the lower arm is turned off, the ON time of the upper arm depends on the voltage of the bootstrap capacitor that supplies power to the drive unit of each switching element of the upper arm. Since this voltage decreases in accordance with the on-time of the upper arm until immediately before, a voltage detection circuit that detects the voltage across this bootstrap capacitor is added to know the current voltage (the time during which the upper arm can be turned on). I needed to.

  When the voltage at both ends of the bootstrap capacitor is less than a certain voltage, the on-off state of the switching element of the upper arm becomes unstable, so the loss of the switching element increases, and in the worst case, the switching element is destroyed. There is. Therefore, the period during which the upper arm is turned on is limited to a period during which the voltage of the bootstrap capacitor is equal to or higher than a certain voltage (allowable discharge voltage).

  However, if a voltage detection circuit is added to detect the allowable discharge voltage, there is a problem that the cost increases. On the other hand, since the lower arm does not use a bootstrap capacitor, there is no such time constraint. However, as described above, since the lower arm is forcibly turned off when the temperature of the switching element becomes equal to or higher than the allowable temperature, there is a problem that it is not possible to apply the dynamic brake using the lower arm when the abnormal temperature rises.

  Also, if the motor winding is short-circuited by the upper arm without using the voltage detection circuit, switching at the maximum load is performed to ensure that the voltage of the bootstrap capacitor is higher than the allowable discharge voltage even when the upper arm is turned on. It is necessary to determine the operable time of the upper arm based on the ON time of the element, and there has been a problem that the operable time becomes extremely short.

JP-A-9-47054 (page 3-4, FIG. 1)

  The present invention solves the above-described problems, and in a motor drive device that performs dynamic braking using an inverter having a temperature protection function, the motor rotation speed is increased by extending the period of dynamic braking by the upper arm as much as possible. And to provide it at a low cost.

In order to solve the above-mentioned problem, the present invention has a plurality of arms each including a switching element for an upper arm and a switching element for a lower arm connected in a totem pole type. An inverter that converts an input DC voltage into an AC voltage and supplies the other end of a plurality of windings provided inside the motor corresponding to the arm and having one end connected in common;
A bootstrap capacitor for accumulating a charge for driving the upper arm;
An inverter control unit that outputs a switching signal to the switching element;
Regenerative power reduction means for reducing the regenerative power generated in the winding when the rotation of the motor is decelerated by connecting the other end of the winding,
The switching signal is provided with a switching period for applying an AC voltage to the winding by turning on and off the switching element and a rest period for not applying the alternating voltage,
The regenerative power reduction unit includes a storage unit in which a maximum operation time, which is a time period from when a predetermined voltage in the bootstrap capacitor is reduced to an allowable discharge voltage at which the upper arm can operate, is stored in advance,
The regenerative power reducing means includes:
A total on-time obtained by summing the times when the upper arms are turned on in the switching period is calculated for each upper arm and stored in the storage unit,
When the regenerative power reducing unit reduces the regenerative power,
Extracting the largest maximum total on-time from the storage means among the total on-times at the same time as the switching period immediately before the start time of the regenerative power reduction process,
From the maximum operation time, calculate the remaining operation time by subtracting the maximum total on-time,
All the upper arms are turned on only during the remaining operation time.

  By using the above means, according to the motor drive device of the present invention, the invention according to claim 1 reduces the rotation speed of the motor by extending the period of the dynamic brake by the upper arm as much as possible, A drive device can be provided at low cost.

1 is a block diagram showing an embodiment of an air conditioner provided with a motor drive device according to the present invention. FIG. 2 is a block diagram illustrating an intelligent power module and its peripheral circuits. FIG. 4 is a block diagram illustrating a regenerative power reduction unit according to the present invention. FIG. 4 is an explanatory diagram illustrating an operation of a regenerative power reduction unit according to the present invention.

  Hereinafter, an embodiment of the present invention will be described in detail as an example based on the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of an air conditioner provided with a motor drive device according to the present invention.
The air conditioner 1 includes an indoor unit 2 and an outdoor unit 3 to which an AC power supply 4 is input, and the indoor unit 2 and the outdoor unit 3 are communicatively connected. The air conditioner 1 includes a compressor, a heat exchanger, a refrigerant circuit, a blower fan, and the like (not shown), but illustration and description are omitted.

  The outdoor unit 3 has a converter 31 that receives the AC power supply 4 and outputs a converted DC power supply, and has a U-phase winding 33U, a V-phase winding 33V, and a W-phase winding 33W wound inside. A three-phase motor 33 having a stator (not shown), one end of each winding of which is connected in common; a motor driving device 5 that drives the motor 33 with the output voltage of the converter 31; An outdoor unit control unit 36 that controls the outdoor unit 3 according to instructions is provided.

  The motor driving device 5 includes three arms having two switching elements (IGBTs) connected in a totem pole type, converts a DC voltage output from the converter 31 into a three-phase AC voltage, An intelligent power module (inverter) 32 that outputs a three-phase AC voltage to each winding and an inverter control unit 35 that outputs a drive signal to the intelligent power module 32 are provided.

  The wiring connecting the intelligent power module 32 and the motor 33 is called a phase line. Further, of the power supply lines connecting the converter 31 and the intelligent power module 32, the positive side is called a P line, and the negative side is called an N line. The phase lines at which the other ends of the windings 33U, 33V, and 33W of the motor 33 are connected to the intelligent power module 32 are referred to as a U-phase line, a V-phase line, and a W-phase line, respectively.

  Further, the motor driving device 5 is provided between the intelligent power module 32 and the inverter control unit 35, and through the intelligent power module 32, the U-phase line and the V-phase line, the V-phase line and the W-phase line, and the U-phase line Power reduction unit (regeneration power reduction means) 20 for reducing the regenerative power generated when motor 33 decelerates by short-circuiting the motor 33 and the W-phase line, respectively. A rotation position detection unit 40 that detects the rotation position. The detected rotation position is output to the regenerative power reduction unit 20 and the inverter control unit 35 as a rotation position signal. Further, the outdoor unit control unit 36 outputs a rotation speed command value, which is the rotation speed of the motor 33, to the inverter control unit 35.

  The inverter control unit 35 performs winding based on the rotation position signal output from the rotation position detection unit 40 so that the rotation speed of the motor 33 approaches the rotation speed of the rotation speed command signal output from the outdoor unit control unit 36. The current supply to 33U, winding 33V, and winding 33W is switched. Further, the inverter control unit 35 executes PWM control for controlling the duty of the switching signal for driving the switching elements of the intelligent power module 32 on and off.

  The intelligent power module 32 has an input terminal 32a to which the positive terminal of the output of the converter 31 is connected, an input terminal 32b to which the negative terminal is connected, and a power terminal 32c to which a driver driving power source 34 for driving each arm is connected. A state terminal 32g to which a temperature abnormality signal for notifying overheating of the internal IGBT is output, a signal terminal 32h to which six switching signals for driving each IGBT are input, and a terminal 32k to which a bootstrap capacitor is connected. Terminals 32j and 32i, and output terminals 32d, 32e, and 32f to which the U-phase line, V-phase line, and W-phase line of the motor 33 are respectively connected.

  The driver drive power supply 34 has a positive terminal connected to the power terminal 32c and a negative terminal connected to the ground. The positive electrode of the bootstrap capacitor 39 is connected to the terminal 32k, the negative electrode is connected to the output terminal 32f, the positive electrode of the bootstrap capacitor 38 is connected to the terminal 32j, the negative electrode is connected to the output terminal 32e, and the positive electrode of the bootstrap capacitor 37 is connected to the terminal. 32i, the negative electrode is connected to the output terminal 32d. The abnormal temperature signal output from the state terminal 32g is output to the regenerative power reduction unit 20 and the inverter control unit 35, respectively.

  FIG. 2 is a block diagram showing the intelligent power module 32 according to the present invention, the connection of the motor 33 and the bootstrap capacitors 37, 38 and 39 connected thereto, and the connection of the driver driving power supply 34. The motor 33 includes a U-phase winding 33U, a V-phase winding 33V, and a W-phase winding 33W, and one end of each winding is commonly connected. Further, switching signals UP, VP, WP, UN, VN, and WN for driving each IGBT are input to the driver for driving each IGBT via the signal terminal 32h.

The intelligent power module 32 has a configuration described below.
The IGBT 61 as the upper arm and the IGBT 71 as the lower arm are connected in a totem pole type, and the emitter terminal of the IGBT 61 and the collector terminal of the IGBT 71 are connected.
Similarly, the IGBT 62 as the upper arm and the IGBT 72 as the lower arm are connected in a totem pole type, and the emitter terminal of the IGBT 62 and the collector terminal of the IGBT 72 are connected.
Similarly, the IGBT 63 as the upper arm and the IGBT 73 as the lower arm are connected in a totem pole type, and the emitter terminal of the IGBT 63 and the collector terminal of the IGBT 73 are connected.

  A freewheeling diode is connected to the collector terminal of each IGBT, and the anode terminal is connected to the emitter terminal of each IGBT. Further, the collector terminal of each IGBT of the upper arm is connected to the P line, and the emitter terminal of each IGBT of the lower arm is connected to the N line (ground).

  The output of a driver 64 that drives the IGBT 61 with the input switching signal UP is connected to the gate terminal of the IGBT 61, and the output of the driver 65 that drives the IGBT 62 with the input switching signal VP is connected to the gate terminal of the IGBT 62. The output of the driver 66 that drives the IGBT 63 with the input switching signal WP is connected to the gate terminal of the IGBT 63. On the other hand, the gate terminal of each IGBT of the lower arm is connected to the output of the driver 67 for the lower arm. The IGBT 71 is driven by the switching signal UN, the IGBT 72 is driven by the switching signal VN, and the IGBT 73 is driven by the switching signal WN.

  In order to supply power to each driver, a power supply terminal 32c is connected to the driver 67 and each anode terminal of the diodes 51, 52 and 53. The cathode terminal of the diode 51 is connected to the terminal 32i and the driver 64 via the resistor 54, the cathode terminal of the diode 52 is connected to the terminal 32j and the driver 65 via the resistor 55, and the cathode terminal of the diode 53 is connected to the resistor 56. Through the terminal 32k and the driver 66.

  On the other hand, the intelligent power module 32 includes a temperature protection unit 57, and outputs a lower arm off signal to turn off all lower arms to the driver 67 when any one of the IGBTs has a temperature equal to or higher than the allowable value. An abnormal temperature signal, which is a pulse signal, is output.

  The intelligent power module 32 is configured as described above. When a voltage of 15.7 volts of the driver driving power supply 34 is applied to each driver via the power supply terminal 32c, the lower arm is turned on or off according to the switching signals UN, VN, WN. On the other hand, the voltage of the driver drive power supply 34 is supplied to the anode terminals of the diodes 51, 52 and 53, and while the lower arm is on, the power supply for driving the upper arm corresponding to the lower arm is maintained. The bootstrap capacitors 37, 38, and 39 can be charged to a predetermined voltage of 15 volts (full charge voltage).

  Therefore, by turning on each lower arm, each bootstrap capacitor is charged, and even if the lower arm is turned off, the charged arm can be used to drive the upper arm. However, when starting up for the first time, it is necessary to turn on the lower arm and charge each bootstrap capacitor before starting operation. When the intelligent power module 32 is used as an inverter, since the upper and lower arms are driven by switching signals that change on and off, the upper arm is driven for a predetermined time, that is, the voltage of the bootstrap capacitor is the lowest voltage that can drive the upper arm. Must be used for a period that does not drop below the allowable discharge voltage value.

FIG. 3 is a block diagram illustrating the regenerative power reduction unit 20 according to the present invention.
The regenerative power reduction unit 20 is a storage unit (storage means) in which a maximum operation time, which is a time from a predetermined voltage (full charge voltage) at the bootstrap capacitor to a permissible discharge voltage at which the upper arm can operate, is stored in advance. 41 and the total ON time, which is the sum of the times when the upper arm was turned on, is calculated for each upper arm and stored in the storage unit 41, and the longest maximum total ON time among the stored is stored in the storage unit 41. An on-time calculating unit (on-time calculating unit) 22 that extracts and outputs the maximum operating time read from the storage unit 41 minus the input maximum total on-time, and the voltage of the bootstrap capacitor drives the upper arm. A remaining time calculating unit (remaining time calculating means) 23 for calculating a remaining time until the voltage reaches a permissible discharge voltage value is provided.

  In addition, the regenerative power reduction unit 20 drives an initial timer unit (initial timer unit) 24 that outputs an initial timer signal that is a pulse signal for the calculated remaining time, an OR circuit (OR unit) 25, and a motor 33. Switching signals UP1, VP1, WP1, UN1, VN1 and WN1 for inputting the signals of the terminals UP2, VP2 and WP2 to which the upper arm signal for short-circuiting each winding of the motor 33 for stopping the motor 33 is input. A signal switching unit (signal switching means) 21 that switches one of the signals of the terminals UN2, VN2, and WN2 to which the lower arm signal is input and outputs the signals as switching signals UP, VP, WP, UN, VN, and WN. It has.

  In addition, the regenerative power reduction unit 20 includes a stop processing time management unit (stop processing time management unit) 26 that manages a stop processing time for short-circuiting each winding of the motor 33 to stop the motor 33, A rotation speed calculation unit (rotation speed calculation means) 30 which calculates the rotation speed (rpm) from the position signal and outputs the rotation speed to the stop processing time management unit 26, and an upper arm signal for turning on the upper arm during the stop processing of the motor 33. An upper arm timer section (upper arm timer means) 28 for outputting, a lower arm timer section (lower arm timer means) 29 for outputting a lower arm signal for turning on the lower arm during the stop processing of the motor 33, and an upper arm timer section 28 and a timer management unit (timer management means) 27 for managing the operation of the lower arm timer unit 29.

  The stop processing time management unit 26 includes an operation stop signal instructed by the inverter control unit 35, a temperature abnormality signal output by the intelligent power module 32, a switching signal UP1, and a rotation speed (rpm) output by the rotation speed calculation unit 30. Are respectively input. On the other hand, the stop processing time management unit 26 outputs a stop processing signal indicating a period for executing the regenerative power reduction processing to the ON time calculation unit 22, the signal switching unit 21, and the timer management unit 27, respectively.

  The first timer unit 24 outputs a first timer signal to the OR circuit 25 and the timer management unit 27, respectively. On the other hand, the upper arm timer 28 receives the upper arm start signal output from the timer manager 27 and outputs the upper arm signal output from the upper arm timer 28 to the OR circuit 25 and the timer manager 27, respectively. Have been. Further, the output of the OR circuit 25 is output to the UP2, VP2, and WP2 terminals of the signal switching unit 21.

  The lower arm timer 29 receives the lower arm start signal output from the timer manager 27, and outputs the lower arm signal output from the lower arm timer 29 to the signals UN2, VN2, and WN2 of the signal switch 21. The signals are output to each terminal and the timer management unit 27, respectively.

Next, the operation of each unit of the regenerative power reduction unit 20 will be described.
When the motor 33 is rotated, the inverter control unit 35 performs a switching period for continuously generating a switching signal that repeatedly turns on and off to apply a voltage to each winding of the motor 33 via the intelligent power module 32, and suspends switching. The rest periods are alternately and repeatedly generated. The switching signals UP1, VP1, and WP1 output from the inverter control unit 35 each have a phase difference of 120 degrees, the switching signals UN1, VN1, and WN1 each have a phase difference of 120 degrees, and the switching signal UP1 , VP1, and WP1, each signal has a phase difference of 180 degrees. In addition, when the upper arm is off and at rest, there is always a timing at which the corresponding lower arm is turned on.Therefore, at this timing, the bootstrap capacitor can be charged to a predetermined voltage, here a full charge voltage. it can. Details of these timings will be described later.

  The on-time calculating unit 22 monitors the next timing when the upper arm is turned on after the suspension period in which the upper arm is turned off, that is, the start of the switching period. The total ON time is calculated for each arm, and the value of each total ON time is stored in the storage unit 41.

  When the stop processing signal output from the stop processing time management unit 26 changes from the low level to the high level, that is, when the process of reducing the regenerative power, which is the stop process of the motor 33, is started, the on-time calculation unit 22 Reads the total ON time of each arm from the storage unit 41. Then, the on-time calculating unit 22 calculates the total on-time of each upper arm in a period that is the same as the switching period from the start time of the regenerative power reduction process. Then, the maximum total on-time, which is the largest value among the total on-time values of the three types of upper arms, is output to the remaining time calculation unit 23. This means that the upper arm with the highest value of the total on-time value has the lowest voltage of the corresponding bootstrap capacitor among the three bootstrap capacitors; This is because the time during which the arm can be turned on the shortest is short.

  On the other hand, in the present embodiment, the inverter control unit 35 controls the three-phase motor. When one phase of the switching signals of the three phases of the upper arm is in the idle period, the other phases are sequentially switched. In this case, it is only necessary to compare the total ON time of the two upper arms and extract only the value of the longer time, so that it is easy to determine the magnitude of the total ON time corresponding to the three upper arms.

  The remaining time calculation unit 23 reads the maximum operation time from the storage unit 41, calculates the remaining operation time by subtracting the input total on-time value from the maximum operation time, and outputs the calculated remaining operation time to the first timer unit 24. The first timer unit 24 outputs an initial timer signal that becomes high level for the remaining operation time to the OR circuit 25, the timer management unit 27, and the stop processing time management unit 26.

  When the first timer signal is input to the OR circuit 25, the OR circuit 25 outputs a high-level signal to each of the UP2, VP2, and WP2 terminals of the signal switching unit 21 while the first timer signal is at the high level. On the other hand, since the lower arm timer unit 29 is not operating at this time, the lower arm signal remains at the low level. Therefore, the terminals UN2, VN2, and WN2 of the signal switching unit 21 are at a low level.

  On the other hand, during the period in which the stop processing signal is at the high level, the signal switching unit 21 replaces the switching signals UP1, VP1, WP1, UN1, VN1, and WN1 with the signals of the terminals UP2, VP2, and WP2 and the signals of UN2, VN2, and WN2. The signal of each terminal is output to the intelligent power module 32 as an UP signal, a VP signal, a WP signal, an UN signal, a VN signal, and a WN signal. Therefore, the upper arm short-circuits the winding of the motor 33 only during the remaining operation time calculated by the remaining time calculation unit 23.

  As described above, the regenerative power reduction unit 20 always detects and sums the time of the pulse width of the switching signal that differs depending on the load of the motor 33 by the on-time calculation unit 22, and sets the maximum on-time of each of the three upper arms to the maximum The total time is extracted, the ON time (remaining operation time) of the upper arm that can be driven by this is calculated, and the winding of the motor 33 is short-circuited for this time.

  On the other hand, as described above, when the temperature protection unit 57 detects an abnormal temperature of any of the IGBTs, the temperature protection unit 57 turns off all the lower arms, so that the winding cannot be short-circuited in the lower arm. Occurs. The regenerative power reduction unit 20, which detects this state with the temperature abnormality signal, continuously switches the upper arm for the maximum time during which the upper arm can be turned on, that is, the time until the voltage of the bootstrap capacitor decreases to the allowable discharge voltage. Turn on to short the winding. Thus, an abnormal voltage rise between the P line and the N line due to the regenerative power can be suppressed, and the circuits of the intelligent power module 32 and the converter 31 can be protected.

  On the other hand, a stop processing signal is input to the permission terminal of the timer management unit 27, and the timer management unit 27 operates only during a period when the stop processing signal is at a high level. A first timer signal is input to the start terminal of the timer management unit 27, and when this signal changes from a high level to a low level, that is, when the first ON of the upper arm by the first timer unit 24 ends. , The timer management unit 27 executes the timer start of the lower arm timer unit 29 and waits for the end of the timer, and immediately after the timer ends, starts the timer of the upper arm timer unit 28 and waits for the end of the timer. . Immediately after the timer ends, the lower arm timer unit 29 starts the timer and waits for the end, and alternately operates the two timer units until the stop processing signal becomes low level.

  The timer management unit 27 outputs a timer start signal to the upper arm timer unit 28, and the upper arm timer unit 28 outputs an upper arm signal that goes high for a predetermined upper arm timer time in accordance with the start signal. The upper arm signal is input to the timer management unit 27, and the timer management unit 27 can detect the end of the timer when the upper arm signal changes from the high level to the low level. Note that the upper arm timer time is a time that is experimentally obtained in advance until the bootstrap capacitor decreases from the predetermined voltage (full charge voltage) to the allowable discharge voltage by continuously turning on the upper arm. The upper arm timer time may be obtained experimentally, or may be calculated from the supply voltage, the wiring impedance, and the capacity of the bootstrap capacitor.

  Further, the timer management section 27 outputs a timer start signal to the lower arm timer section 29, and the lower arm timer section 29 outputs a lower arm signal which becomes high level for a predetermined lower arm timer time according to the start signal. . The lower arm signal is input to the timer management unit 27, and the timer management unit 27 can detect the end of the timer when the lower arm signal changes from the high level to the low level. The lower arm timer time is a time obtained by experimentally obtaining a time required for each bootstrap capacitor to rise from an allowable discharge voltage to a predetermined voltage (full charge voltage). The lower arm timer time may be obtained experimentally, or may be calculated from the supply voltage, the wiring impedance, and the capacity of the bootstrap capacitor.

  The stop processing time management unit 26 receives the operation stop signal output from the inverter control unit 35 and the abnormal temperature signal output from the intelligent power module 32, respectively. The operation stop signal indicates an instruction of the indoor unit 2 or an operation stop of the air conditioner 1 determined by the outdoor unit control unit 36, and a temperature abnormality signal is a temperature abnormality of the intelligent power module 32 regardless of such an instruction. Means

  When the temperature abnormality signal is input, the stop processing time management unit 26 determines that the regenerative power reduction by the lower arm cannot be executed, and executes only one winding short-circuit processing by the upper arm. In this case, the stop processing time management unit 26 recognizes that the first winding short circuit by the upper arm has been completed when the input first timer signal changes from the high level to the low level, and changes the stop processing signal from the high level. Set to low level.

On the other hand, when only the operation stop signal is input without the temperature abnormality signal being input, the stop processing time management unit 26 determines that the regenerative power reduction by the lower arm can be used, and the first timer unit 24 turns on the upper arm. Is completed, alternate winding short-circuit processing by the lower arm / upper arm is executed. In this case, the stop processing time management unit 26 ignores the input first timer signal.
In addition, when the operation stop signal is input, the stop processing time management unit 26 performs alternate winding short-circuit processing by the upper arm / lower arm for the stop time determined by the load state and the rotation speed of the motor 33. Next, a method of calculating the stop time will be described.

  The stop processing time management unit 26 receives the switching signal UP1 and the rotation speed signal, and the stop processing time management unit 26 calculates the pulse width of the latest switching signal UP1 (the time when the IGBT 61 is turned on) and the latest rotation speed. Is always stored in the storage unit 41. Then, when the operation stop signal is input, the stop processing time management unit 26 reads the pulse width and the rotation speed (rpm) of the immediately preceding switching signal UP1 from the storage unit 41. The pulse width of the switching signal UP1 is a result of the PWM control, and the pulse width indicates the magnitude of the load of the motor 33. The relationship between the load torque (unit: Newton meter), which is the magnitude of this load, and this pulse width is experimentally obtained in advance, and is stored in the storage unit 41 as a comparison table.

Next, a method of calculating the winding short-circuit processing time for suppressing the regenerative voltage will be described.
Short-circuit processing time: t (unit is seconds),
Moment of inertia of motor 33: Jm (unit is kilogram square meter),
Rotation speed immediately before braking of the motor 33: N (unit is rotation speed / minute),
Load torque: When specified as TL (unit is Newton meters),

Short circuit processing time: t = Jm × N / (9.55 × TL) (1)

As the moment of inertia: Jm, a value described in the specification of the motor 33 is stored in the storage unit 41 in advance. Then, the stop processing time management unit 26 receives the rotation speed: N from the rotation speed calculation unit 30 and compares the load torque: TL with the pulse width of the switching signal UP1 stored in the storage unit 41 as described above. The short-circuit processing time: t is calculated by substituting these values into Equation 1 and calculating the short-circuit processing time, and the stop processing signal is set to the high level for the calculated time.
Note that, for simplicity, the short-circuit processing time may be a stop time from the highest speed of the motor 33 obtained in advance by an experiment.

Next, the operation of the regenerative power reduction unit 20 according to the present invention will be described with reference to the explanatory diagram of FIG.
The horizontal axis in FIG. 4 is time. 4 (1) output to the intelligent power module 32 on the vertical axis of FIG. 4 is an UP signal, FIG. 4 (2) is a VP signal, FIG. 4 (3) is a WP signal, FIG. 4 (4) is an UN signal, FIG. 4 (5) shows the VN signal, and FIG. 4 (6) shows the WN signal.

  4 (7) shows the voltage across the bootstrap capacitor 37, FIG. 4 (8) shows the voltage across the bootstrap capacitor 38, and FIG. 4 (9) shows the voltage across the bootstrap capacitor 39 on the vertical axis. .

4 (10) is an operation stop signal, FIG. 4 (11) is a stop processing signal, FIG. 4 (12) is an initial timer signal, and FIG. 4 (13) is an upper arm signal on the vertical axis of FIG. 4 (14) shows the lower arm signal, FIG. 4 (15) shows the input voltage of the intelligent power module 32, and FIG. 4 (16) shows the temperature abnormal signal. It should be noted that t0t to 15 indicate time.
First, the operation when the operation stop signal is output will be described, and after that, the case where the abnormal temperature signal is output will be described.

  The UP signal, the VP signal, the WP signal, the UN signal, the VN signal, and the WN signal in the period from t0 to t11 are switching signals for rotating the motor 33 via the intelligent power module 32, and the operation stop signal or the temperature abnormality signal is output. It is output until t11 when it changes from low level to high level. When the operation stop signal or the temperature abnormality signal is at a low level, the switching signals UP1, VP1, WP1, UN1, VN1, and WN1 selected by the signal switching unit 21 are output to the intelligent power module 32 as they are.

  The inverter control unit 35 configures and controls one cycle such that a period twice as long as the PWM-modulated switching period for each of the switching signals UP1, VP1, and WP1 continues as a low-level rest period, The timing of each switching signal is sequentially shifted every 120 degrees. Further, the switching signals UN1, VN1, and WN1 are similarly shifted in phase every 120 degrees. The inverter control unit 35 controls the switching signals UN1, VN1, and WN1 so that the switching signals UP1, VP1, and WP1 have a phase delay of 180 degrees.

  For this reason, for example, the voltage of the bootstrap capacitor 37 falls as shown in FIG. 4 (7) in a period from t8 when the UP signal starts switching to t10 when the switching ends. On the other hand, during the period from t6 to t10 when the VP signal is turned off, the VN signal, which is a signal of the lower arm corresponding to the upper arm, is at a low level at t6 to t7 and t9 to t10, and the VP signal Can be charged to a predetermined voltage (full charge) by at least t10. The switching of the WP signal ends at t8, and the bootstrap capacitor 39 can be charged to a substantially predetermined voltage from t8 to t11.

  The on-time calculation unit 22 calculates the operation stop signal calculated for each of the switching signals UP1, VP1, and WP1, or the three totals in the on-time totaling period (the same length as the switching period) that is a predetermined period immediately before the occurrence of the temperature abnormality signal. Extract the longest maximum total on-time from the on-time. More specifically, the total ON time of each of the UP signal, the VP signal, and the WP signal (switching signals UP1, VP1, and WP1) in the period from t8.5 to t11, which is the same time as the switching period, is calculated. In this case, the UP signal is t8.5 to t10, the VP signal is t10 to t11, the WP signal is zero (no ON signal), and the total ON time of the UP signal is the longest. That is, the voltage of the bootstrap capacitor is the lowest in the upper arm, and when the upper arm is turned on next, the ON time needs to be the shortest among the three upper arms.

  In the case of the example of FIG. 4, the UP signal uses the upper arm for one switching period from t8 to t10. Therefore, at time t10, only the voltage of the bootstrap capacitor 37 corresponding to the total on-time from t8 to t10 is reduced. On the other hand, in the present embodiment, only the period from t8.5 to t10 is compared with the total on-time, and the period from t8 to t8.5 is excluded from the total on-time, and the voltage drop during this period is considered. Not. On the other hand, t10 to t11 are during the charging period of the bootstrap capacitor 37, and are periods during which the voltage of the bootstrap capacitor 37 rises. Therefore, in the present embodiment, this is simply regarded as an offset and is excluded from the calculation.

  In order to reduce the error in canceling the voltage drop due to the voltage drop and the voltage rise due to charging, a value obtained by multiplying the total on-time in the period from t8 to t8.5 by a predetermined coefficient for reducing the error experimentally obtained in advance is used. It may be added to the total ON time from t8.5 to t10. Alternatively, the total on-time corresponding to the difference between the voltage rises from t10 to t11 is subtracted from the total on-time during the period from t8 to t8.5, and the total on-time during the period from t8.5 to t10 is added to the result. It may be.

  Then, the on-time calculating unit 22 extracts the longest maximum on-time total from the total on-time of the UP signal obtained in this way and the total on-time of the VP signal and the WP signal obtained in the same manner. The remaining time calculation unit 23 outputs the remaining operation time from t11 to t12 when the UP signal can be turned on after t11, and outputs the remaining operation time to the first timer unit 24. The first timer section 24 outputs a first timer signal for the remaining operation time as shown in FIG.

  After t11 when the operation stop signal or the temperature abnormality signal changes from low level to high level, the stop processing signal becomes high level. Therefore, the signal switching unit 21 switches the switching signals UP1, VP1, WP1, UN1, VN1, WN1 to UP2. The signals are switched to the signals input to the terminals VP2, WP2, UN2, VN2, and WN2. Therefore, the signal switching unit 21 outputs an ON signal (high-level signal) as the UP signal, the VP signal, and the WP signal during the period from t11 to t12. On the other hand, a low level is input to each of the terminals UN2, VN2, and WN2 because the lower arm timer unit 29 is not operated, and the signal switching unit 21 outputs the UN signal, the VN signal, and the WN signal at a low level.

  Therefore, each winding of the motor 33 is short-circuited by the upper arm during t11 to t12, which is the high-level period of the first timer signal. Thereby, as shown in FIG. 4 (15), the peak of the input voltage of the intelligent power module 32 is reduced from 550 volts when the regenerative voltage is not short-circuited to 390 volts, and the switching element in the converter 31 and the intelligent power module 32 And the return diode and the like can be prevented from being damaged.

  On the other hand, when the remaining operation time ends and the first timer signal changes from the high level to the low level, the timer management unit 27 starts operating, and the lower arm timer unit 29 outputs the lower arm signal that becomes the high level for the lower arm timer time. Output. At this time, since the first timer section 24 and the upper arm timer section 28 have stopped their operations, the output signals are both at the low level. Therefore, the signal switching unit 21 outputs the UP signal, the VP signal, and the WP signal at a low level and the UN signal, the VN signal, and the WN signal at a high level during the lower arm timer time from t12 to t13.

  Then, the timer management unit 27 alternately outputs the upper arm signal and the lower arm signal so that the upper arm and the lower arm are alternately turned on until t15 when the stop processing signal changes from the high level to the low level. In addition, the stop processing time management unit 26 calculates the short-circuit processing time by using the above-described equation 1, and after the operation stop signal changes from the low level to the high level, sets the stop processing signal to the high level for the short-circuit processing time. After that, set to low level.

  Next, a case where the temperature abnormal signal shown in FIG. 4 (16) is output from the intelligent power module 32 at t11 will be described. In this case, until t12, the same processing as when the operation stop signal is input to the stop processing time management unit 26 is performed. That is, the first timer unit 24 turns on the upper arm for the remaining operation time.

  On the other hand, when the temperature abnormality signal is input to the stop processing time management unit 26, when the first timer signal changes from the high level to the low level at t12, the stop processing time management unit 26 changes the stop processing signal from the high level to the low level. Thus, the regenerative power reduction processing is completed. This is because, as described above, when the temperature of the intelligent power module 32 is abnormal, control by the lower arm cannot be performed. For this reason, although the braking of the motor 33 cannot be performed to the end, the rise of the input voltage of the intelligent power module 32 due to the short-circuit of the winding by the upper arm can be reduced.

  Then, the stop processing time management unit 26 changes the stop processing signal from high level to low level to stop the operation of the timer management unit 27, and the signal switching unit 21 switches the switching signals UP1, VP1, WP1, UN1, VN1, WN1. Select and output. Note that the inverter control unit 35 sets all the switching signals to low level in order to stop the operation of the inverter when the temperature abnormality signal is input. Therefore, the UP signal, the VP signal, the WP signal, the UN signal, the VN signal, and the WN signal all become low level.

As described above, even when all the lower arms are turned off by the temperature protection unit 57, the regenerative power reduction unit calculates the remaining operation time during which the upper arm can be reliably turned on and calculates the remaining operation time by this time. Is turned on, the voltage of the bootstrap capacitor does not fall below the allowable discharge voltage. Therefore, as described in the background art, an operable time longer than the operable time of the upper arm determined shorter in consideration of the maximum load can be obtained.
In addition, since the calculation of the remaining operation time and the timer function can be realized by software, the voltage can be reduced because the voltage detection circuit for detecting the allowable discharge voltage described in the background art is unnecessary.

In the present embodiment, an example in which the motor driving device 5 is applied to the air conditioner 1 is described. However, the present invention is not limited to this, and may be applied to a motor driving device of a washing machine.
Further, in the present embodiment, the regenerative power reduction unit 20 is described as hardware, but this may be realized by software.
In this embodiment, the temperature protection of the switching element is described as a protection function of the intelligent power module 32. However, the present invention is not limited to this, and other protection functions such as an overcurrent protection function of the switching element are comprehensively provided. It may be provided. Even if these protection functions operate and the lower arm cannot be used, the same effect as the present invention can be obtained.

DESCRIPTION OF SYMBOLS 1 Air conditioner 2 Indoor unit 3 Outdoor unit 4 AC power supply 5 Motor drive device 20 Regenerative power reduction part (regenerative power reduction means)
21 Signal switching unit (signal switching means)
22 ON-time calculating unit (ON-time calculating means)
23 Remaining time calculator (remaining time calculator)
24 First timer section (First timer means)
25 OR circuit (OR means)
26 stop processing time management unit (stop processing time management means)
27 Timer management unit (Timer management means)
28 Upper arm timer (upper arm timer means)
29 Lower arm timer section (lower arm timer means)
30 Revolution calculating section (revolution calculating means)
31 converter 32 intelligent power module (inverter)
32a input terminal 32b input terminal 32c power terminal 32d output terminal 32e output terminal 32f output terminal 32g state terminal 32h signal terminal 32i terminal 32j terminal 32k terminal 33 motor 33U winding
33V winding
33W winding
34 Driver drive power supply 35 Inverter control unit 36 Outdoor unit control unit 37, 38, 39 Bootstrap capacitor 40 Rotational position detection unit 41 Storage unit (storage means)
51, 52, 53 Diodes 54, 55, 56 Resistance 57 Temperature protection unit 61, 62, 63 IGBT
64 drivers, 65, 66, 67 drivers 71, 72, 73 IGBT

Claims (1)

It has a plurality of arms composed of a switching element for the upper arm and a switching element for the lower arm connected in a totem pole type, and converts the input DC voltage to an AC voltage to inside the motor corresponding to the arm. An inverter provided to supply the other end of the plurality of windings having one end connected in common;
A bootstrap capacitor for accumulating a charge for driving the upper arm;
An inverter control unit that outputs a switching signal to the switching element;
Regenerative power reduction means for reducing the regenerative power generated in the winding when the rotation of the motor is decelerated by connecting the other end of the winding,
The switching signal is provided with a switching period for applying an AC voltage to the winding by turning on and off the switching element and a rest period for not applying the alternating voltage,
The regenerative power reduction unit includes a storage unit in which a maximum operation time, which is a time period from when a predetermined voltage in the bootstrap capacitor is reduced to an allowable discharge voltage at which the upper arm can operate, is stored in advance,
The regenerative power reducing means includes:
A total on-time obtained by summing the times when the upper arms are turned on in the switching period is calculated for each upper arm and stored in the storage unit,
When the regenerative power reducing unit reduces the regenerative power,
Extracting the largest maximum total on-time from the storage means among the total on-times at the same time as the switching period immediately before the start time of the regenerative power reduction process,
From the maximum operation time, calculate the remaining operation time by subtracting the maximum total on-time,
A motor drive device wherein all the upper arms are turned on only during the remaining operation time.

Images