JP2006223014A - Motor drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor drive device capable of attaining size and cost reduction and high efficiency. <P>SOLUTION: This drive device includes a rectification circuit 4 having a capacitor with a small capacity with an AC power supply 1 as an input; an inverter 5 connected to the rectification circuit 4; a motor 6 driven by the inverter 5; an inverter controller 17 for controlling the inverter 5; a position detector 18 for detecting a position of the motor 6; a controller 19 for determining a commanded rotational speed of the motor 6; and an inverter power switch 22 for supplying power to the inverter 5 or stopping it. When a rotational speed determined by the controller 19 is 0 r/s (stopping), the power supply of the inverter 5 is shut down by an inverter power switch 22, so that the loss of the motor drive device is suppressed during motor stopping to suppress the power consumption of the device. Because the capacity of the capacitor of the rectification circuit 4 is small, a harmonic current can be suppressed and the use of a harmonic accommodation circuit can be eliminated, thus attaining size and cost reduction in the device. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a motor drive device by inverter control.

  Conventionally, this type of motor drive device cuts off the power supply of the AC / DC converter for supplying power to the inverter circuit in order to reduce power consumption while the motor is stopped (see, for example, Patent Document 1). ).

  FIG. 8 shows a conventional motor driving apparatus described in Patent Document 1. In FIG. As shown in FIG. 8, the commercial power source 101 is, for example, a 100V 50 Hz or 60 Hz AC power source in a general home. A rectifier circuit 102 such as a diode bridge rectifies the commercial power supply 101. The electrolytic capacitor 103 smoothes the output voltage from the rectifier circuit 102.

  The inverter 104 uses the output voltage of the electrolytic capacitor 103 as a power source, and the compressor 105 is operated by the inverter 104. A contact-type temperature sensor 106 such as a bimetal is disposed in the cabinet and detects the temperature in the cabinet.

  The AC / DC converter 107 inputs both ends of the AC power supply line on the input side of the rectifier circuit 102, and is constituted by a transformer or the like. The control unit 108 uses the output of the AC / DC converter 107 as a power input and receives the compressor operation command cutoff means to control the inverter 104.

  Next, the operation of the refrigerator control device configured as described above will be described.

  After the power is turned on, when the refrigerator interior temperature t is higher than the set temperature T, the temperature sensor 106 is turned on, the AC / DC converter 107 is operated, and power is supplied to the control unit 108. Next, an operation command is output from the control unit 108, and the compressor 105 is operated by the inverter 104.

  When the refrigerator internal temperature t is lower than the set temperature T, the temperature sensor 106 is turned OFF and the input to the AC / DC converter 107 is shut off. Next, the power supply to the control unit 108 is also cut off, and the compressor 105 stops. Thus, the refrigerator is controlled by the operation in which the compressor 105 repeats ON / OFF according to the internal temperature.

  When the compressor 105 is stopped by the operation as described above, the temperature sensor 106 is in a position that does not depend on the AC power supply input to the rectifier circuit 102, so that the electrolytic capacitor 103 remains charged. Next, when the internal temperature rises and the compressor 105 restarts, the electric charge of the electrolytic capacitor 103 is in a charged state, so that a large inrush current does not flow.

As described above, when the compressor 105 is restarted, the electrolytic capacitor 103 is charged and a large inrush current does not flow. Therefore, it is not necessary to provide an inrush current prevention circuit, and the input of the AC / DC converter 107 is not required when the compressor 105 is stopped. Therefore, it is possible to provide a refrigerator control device that can further reduce power consumption when the compressor 105 is stopped.
JP-A-11-101541

  However, in the above case, the power consumption when the compressor 105 is stopped can be made almost zero, but the temperature control itself has a problem that the temperature accuracy deteriorates because it relies on the contact temperature sensor 106. Furthermore, since this configuration requires a large-capacity electrolytic capacitor 103 in the smoothing circuit, when the compressor 105 is driven, the power supply current includes a harmonic component, and a passive filter or an active filter is included in the power supply unit to suppress the harmonic current. Insertion is required, and there is a problem that increases the cost and size of the circuit.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems, and to provide a motor drive device that realizes small size, low cost, and low power consumption.

  In order to achieve the above object, a motor driving device of the present invention is driven by an AC power source, a rectifier circuit having a small-capacitance capacitor with the AC power source as an input, an inverter connected to the rectifier circuit, and the inverter. A motor, an inverter control unit for controlling the inverter, position detection means for detecting the position of the motor and outputting it to the inverter control unit, and determining a command rotational speed of the motor and outputting it to the inverter control unit A control means, and an inverter power switch operated by the control means for supplying or stopping power to the inverter, and when the rotational speed determined by the control means is stopped, the control means The switch is operated to shut off the power source of the inverter.

  As a result, power consumption by the inverter when the motor is stopped can be eliminated. Furthermore, since the capacitor capacity is very small, no harmonic current is generated, so that no passive filter or active filter is required, and the system can be reduced in size and cost.

  Since the motor drive device of the present invention cuts off the power supply to the inverter while the motor is stopped, the power consumption of the motor drive device can be reduced, and the smoothing circuit uses a very small capacitor. Therefore, there is no influence of the inrush current due to the charging of the capacitor when the power is supplied again to the inverter, and the harmonic current can be eliminated, so that the circuit can be reduced in size and cost.

  Further, when the motor is driven, the motor rotational speed is instructed after a predetermined time has elapsed after power is supplied to the inverter, so that the startability of the motor can be improved.

  In addition, the second communication means sends to the control means via the first communication means that the motor can be driven after supplying power to the inverter circuit, and the control means is in a state where the inverter circuit can drive the motor. After confirming that, the first communication means supports the motor rotation speed to the commutation means via the second communication means, so that the motor can be reliably started.

  In addition, if there is no response from the inverter control unit even after a certain period of time has elapsed since the power supply to the inverter, the inverter control unit power is shut off and supplied again to initialize the inverter control unit and then the motor again. Since the activation is performed, the reliability of the motor driving device can be improved.

  In addition, since a warning is issued when a motor drive abnormality is detected by the display means, serviceability can be improved by notifying the user of the abnormality.

  In addition, since the inverter power switch is installed from the commercial power source through the filter circuit, the motor drive device can be reduced in size and cost.

  Further, by adopting a brushless DC motor having a permanent magnet as a stator of the motor, the efficiency of the system can be increased.

  In addition, since the motor drives the compressor of the refrigerator or the air conditioner, the power consumption when the compressor is stopped can be reduced, so that a product with low power consumption can be provided.

  The invention of the motor drive device according to claim 1 includes an AC power supply, a rectifier circuit having a small-capacitance capacitor with the AC power supply as an input, an inverter connected to the rectifier circuit, and a motor driven by the inverter. An inverter control unit that controls the inverter; a position detection unit that detects the position of the motor and outputs the detected position to the inverter control unit; and a control unit that determines the command rotational speed of the motor and outputs the command to the inverter control unit And an inverter power switch operated by the control means for supplying or stopping power supply to the inverter, and when the rotational speed determined by the control means is stopped, the control means turns the inverter power switch Operates to shut down the inverter power supply and eliminates inverter circuit loss when the motor is stopped. It can become possible, to reduce the power consumption of the motor driving device.

  According to a second aspect of the present invention, in addition to the first aspect, the first communication means for transmitting the number of revolutions of the motor determined by the control means, and the first communication means And when the motor is driven from a state in which the motor is stopped and the power supply of the inverter is cut off, The control means operates the inverter power switch to supply power to the inverter, and thereafter, after a predetermined time has elapsed, the command rotational speed of the motor determined by the control means is determined by the first communication means and the first communication means. 2 is sent to the inverter control unit via the communication means, and the motor is driven at the command rotational speed, after power is supplied to the inverter circuit, after the inverter power supply circuit is stabilized, and After the initialization of the control unit has ended reliably, for instructing driving of the motor, it is possible to improve the motor starting characteristics.

  According to a third aspect of the present invention, there is provided the motor drive device according to the first or second aspect, wherein the inverter control unit can drive the motor via the second communication means and the first communication means. Is transmitted to the inverter control unit after confirming that the inverter control unit is ready to drive the motor. After confirming that the inverter circuit is in a state where the motor can be driven, the motor is instructed, so that reliable start-up can be ensured and response from the inverter power supply to the start of motor driving can be increased.

  According to a fourth aspect of the present invention, there is provided a motor drive device according to any one of the first to third aspects, wherein after the control means supplies power to the inverter to drive the motor, If there is no response from the inverter controller even after the elapse of time, the inverter is judged to be abnormal, the inverter power supply is shut off, and then power is supplied to the inverter again. In the case of an abnormal initialization or the like, the inverter power supply is shut off and the inverter system is initialized again, so that the startability can be improved and the start-up failure can be reduced, thus improving the reliability of the motor drive device. be able to.

  In addition to the invention according to any one of claims 1 to 4, the invention of the motor drive device according to claim 5 includes display means for displaying the drive state of the motor, and the control means includes: When an abnormality in the motor drive is detected, a warning is displayed on the display means, and the user can easily recognize the abnormality in the motor drive device, thereby improving serviceability.

  In addition to the invention according to any one of claims 1 to 5, the motor drive device according to claim 6 prevents noise generated from the inverter from flowing out to the commercial power supply, It has a filter circuit for preventing noise inflow from the commercial power supply, and the filter circuit is directly connected to the commercial power supply. Since the filter circuit of the control unit and the inverter unit can be used together, the motor drive device can be reduced in size. And cost reduction.

  According to a seventh aspect of the present invention, there is provided a motor drive device according to any one of the first to sixth aspects, wherein the motor according to any one of the first to sixth aspects is a brushless DC motor having a permanent magnet in a rotor. The efficiency of the drive system can be increased and the power consumption can be further reduced.

  According to an eighth aspect of the present invention, the motor according to any one of the first to seventh aspects drives the compressor, and the compressor of the refrigerator or the air conditioner is stopped. The power consumption of the product can be reduced by reducing the power consumption at the time.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same reference numerals are given to the same configurations as those of the conventional example or the embodiments described above, and detailed descriptions thereof will be omitted. The present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a block diagram of a motor drive device according to Embodiment 1 of the present invention.

  In FIG. 1, an AC power source 1 is a general commercial power source of 100 V 50 Hz or 60 Hz in the case of Japan. The rectifier bridge 2 is a bridge connection of four diodes.

  The small-capacitance capacitor 3 is a 1 μF multilayer ceramic capacitor. In recent years, multilayer ceramic capacitors have come to be realized with a chip having a high withstand voltage and a large capacity. Conventionally, an electrolytic capacitor having a large capacity (several hundred μF in the case of 200 W output) has been mainly used for this capacitor, so that a very small driving device can be realized. A circuit combining the rectifier bridge 2 and the capacitor 3 is a rectifier circuit 4.

  Conventionally, this capacitor generally has the ripple resistance of the smoothing capacitor due to the ripple content of the DC voltage and the ripple current from the output capacity (W or VA) of the inverter 5 and the input capacity (W or VA) of the entire driving device. Determine the capacitance of the capacitor from the characteristics. In consideration of these conditions, a capacity of about 2 to 4 μF / W is generally secured. That is, in the case of an output capacity of 200 W, an electrolytic capacitor of about 400 to 800 μF was used.

  On the other hand, in the first embodiment, a capacitor having a capacitance of 0.1 μF / W or less is used as the capacitor 3. That is, in the case of an output capacity of 200 W, a capacitor of 20 μF or less is used.

  The inverter 5 is a six-circuit three-phase bridge connected to a set of diodes connected in the opposite direction to the switching element IGBT.

  The motor 6 is driven by the three-phase output of the inverter 5. The stator of the motor 6 is provided with a three-phase star-connected winding. This winding method may be concentrated winding or distributed winding. The arrangement method may be a surface magnet type (SPM) or a magnet embedded type (IPM), and the permanent magnet may be a ferrite or a rare earth.

  The motor of the first embodiment is a brushless DC motor in which a permanent magnet is arranged on the rotor, but it may be an induction motor or a synchronous reluctance motor.

  The compression element 7 is connected to the rotor shaft of the motor 6 and sucks, compresses and discharges the refrigerant gas. The motor 6 and the compression element 7 are accommodated in the same hermetic container to constitute the compressor 8.

  The discharge gas compressed by the compressor 8 constitutes a refrigeration air conditioning system that returns to the suction of the compressor 8 through the condenser 9, the decompressor 10, and the evaporator 11. At this time, the condenser 9 dissipates heat and the evaporator 11 absorbs heat, so that cooling and heating can be performed. If necessary, a blower or the like may be used for the condenser 9 or the evaporator 11 to further promote heat exchange.

  The position detector 12 detects the rotational position of the rotor of the motor 6 from the induced voltage or motor current of the motor 6. In the first embodiment, the rotational position of the rotor is detected from the induced voltage. The inverter 5 is a 120-degree energized rectangular wave PWM inverter, and detects the zero-cross point of the induced voltage from a phase that is not always energized. Although a method for detecting the rotational position will be described, a driving method may be used in which an arbitrary waveform with a conduction angle of 120 degrees or more and 180 degrees or less is generated and the relative position of the rotor is detected from the motor current.

  The position estimation means 13 performs time measurement of the detection timing when the position detection means 12 normally detects the position. Based on this timing time, position estimation is performed to output a drive output.

  The voltage detection means 14 detects the voltage across the capacitor 3 and determines whether the voltage value is larger or smaller than a predetermined value set in advance. The switching means 15 receives the output of the voltage detection means 14 as an input, selects either the position detection means 12 or the position estimation means 13 and outputs it.

  The commutation means 16 receives the output of the switching means 15 and controls ON / OFF of the six IGBTs of the inverter 5. The inverter control unit 17 includes the position detection unit 12, the position estimation unit 13, the voltage detection unit 14, the switching unit 15, and the commutation unit 16, and performs control for driving the motor 6 by the inverter 5.

  The thermistor 18 detects the temperature of each part, and in the first embodiment, the temperature inside the refrigerator is detected.

  The control means 19 determines the stop and operation of the compressor 8 from the temperature information detected by the thermistor 18, determines the compressor drive speed during operation, and determines the compressor drive speed determined by the first communication means 20. Is transmitted to the inverter control unit 17. The second communication means 21 receives the data transmitted from the first communication means 20 and sends it to the inverter control unit.

  The first communication means 20 and the second communication means 21 are configured to be able to transmit and receive, and the communication method may be either serial communication or parallel communication.

  The inverter power switch 22 is a power supply switch for the inverter circuit portion below the rectifier circuit. When the compressor is stopped by the control means 19, the inverter drive power is shut off by the switch drive means 23, and the compressor is in the operating state. In this case, the switch drive means 23 supplies power to the inverter circuit. The display means 24 gives a warning display when the control means 19 detects an abnormality in the inverter circuit.

  The control power supply circuit 25 is a power supply for the thermistor 18, the control means 19, the first communication means 20, the switch drive means 23, and the display means 24, and is constituted by an AC / DC converter.

  The inverter power supply circuit 26 includes a second rectifier circuit 27 configured by a rectifier diode (not illustrated) and a smoothing capacitor (not illustrated), and a DC / DC converter 28. The inverter controller 17 and the second communication circuit This is a power supply for the means 21.

  The inverter power supply circuit 26 absorbs the regenerative energy generated when the motor 6 stops suddenly due to out-of-step or the like by the smoothing capacitor of the second rectifier circuit 27, prevents the feedback to the inverter circuit by the rectifier diode, and absorbs the regenerated energy absorbed. Is consumed by the DC / DC converter 28, so that destruction of the inverter due to regenerative energy is prevented.

  The capacity of the smoothing capacitor is determined by the regenerative energy of the motor and the output of the second power supply circuit. However, when the maximum rotational speed is about 80 r / s, it becomes about 0.1 μF / 2 W (motor output).

  The filter circuit 29 is directly connected to the AC power source 1, and the rectifier circuit 4, the inverter 5, the motor 6, and the inverter power source circuit 26 that are components of the inverter circuit are connected to the rear side of the filter circuit via an inverter power switch. . The control power circuit is connected in parallel with the inverter circuit and branches between the filter circuit and the inverter power switch.

  As a result, since the control unit composed of the control power circuit 25, the control unit 19, the first communication unit 20, the sensor 18, the SW drive unit 23, and the display unit 24 can be used as the filter circuit of the inverter circuit unit, the motor drive The system has been reduced in size and cost.

  The operation of the motor driving apparatus configured as described above will be described.

  The AC power source 1 is full-wave rectified by the rectifier bridge 2, but the capacitor 3 has a very small capacity compared to the conventional one, so its output voltage (voltage across the capacitor 3) is not smoothed and has a large ripple. It will be.

  Since the position detecting means 14 detects the rotational position of the rotor of the motor 6 from the induced voltage or the motor current, when the output voltage of the rectifier bridge 2 is low, a desired voltage or current cannot be sufficiently secured. Position detection is impossible.

  On the other hand, the position estimation means 13 always detects the position detection timing of the position detection means 12 and outputs a position estimation signal at the same timing as the previous timing when no position detection signal is input.

  If the voltage across the capacitor 3 detected by the voltage detection means 12 is higher than a preset value (50 V in the first embodiment), the switching means 15 selects and switches the signal of the position detection means 12. To the commutation means 16. Conversely, if it is lower than the predetermined value, the switching means 15 selects / switches the signal of the position estimating means 13 and outputs it to the commutation means 16.

  Although not shown here, the voltage detection means 14 detects that the voltage across the capacitor 3 changes, feed-forward control is performed to the duty of the PWM control of the output, and the output voltage or current of the inverter 5 is calculated. Control to keep it constant.

  That is, when the voltage across the capacitor 3 is higher than the base duty obtained by speed control, the duty is lowered, and conversely, when the voltage is lower, the duty is increased to adjust the output voltage or current, thereby adjusting the motor 6. Drive smoothly.

  Next, voltage waveforms at both ends of the capacitor 3 will be described with reference to FIGS. FIG. 2 is a timing chart showing a voltage waveform of capacitor 3 of the motor drive device according to the first embodiment of the present invention.

  In FIG. 2, the vertical axis represents voltage, and the horizontal axis represents time. The AC power source 1 was a 100 V 50 Hz AC power source.

  In the voltage waveform shown by the dotted line A in FIG. 2, when the load current is very small (almost no current flows), the charge of the capacitor 3 is hardly used and the voltage is hardly lowered. However, the load current here is the output current of the rectifier circuit, that is, the input current to the inverter 5.

  The average voltage is 141 V, the ripple voltage is 0 V, and the ripple content is 0%. In addition, a ripple voltage and a ripple content rate shall be defined as the following (Formula 1) (Formula 2).

次に負荷電流を大きくしていくとコンデンサ３の充電電荷が使われ、図２の一点鎖線Ｂに示す電圧波形のように瞬時最低電圧が低下してくる。ただし、電源電圧から決まる瞬時最高電圧は１４１Ｖで変わらない。

Next, when the load current is increased, the charge of the capacitor 3 is used, and the instantaneous minimum voltage decreases as shown by the voltage waveform shown by the one-dot chain line B in FIG. However, the instantaneous maximum voltage determined from the power supply voltage does not change at 141V.

  In the case of the voltage waveform shown by the alternate long and short dash line B, since the instantaneous minimum voltage is 40V, the average voltage is about 112V, the ripple voltage is 101V, and the ripple content is 90%.

  When the load current is further increased, almost no charge is stored in the capacitor 3, and the instantaneous minimum voltage decreases to almost 0V as shown by the voltage waveform shown by the solid line C in FIG. However, the instantaneous maximum voltage determined from the power supply voltage is 141 V and does not change. In the case of the voltage waveform shown by the solid line C, the instantaneous minimum voltage is 0V, so the average voltage is about 100V, the ripple voltage is 141V, and the ripple content is 141%.

  In this way, when the capacitor 3 has a small capacity, when the load current is taken out, the input AC power supply 1 is not fully smoothed but a waveform obtained by full-wave rectification.

  Next, the relationship between the load current, the instantaneous minimum voltage, and the ripple content will be described in more detail with reference to FIG. FIG. 3 is a characteristic diagram showing the load current and the instantaneous minimum voltage / ripple content of the motor drive apparatus according to the first embodiment.

  In FIG. 3, the horizontal axis represents the load current, and the vertical axis represents the instantaneous minimum voltage and the ripple content. Further, the solid line indicates the instantaneous minimum voltage characteristic, and the broken line indicates the ripple content ratio characteristic.

  In the case of the current waveform indicated by the dotted line A described in FIG. 2, the load current is 0 A, the instantaneous minimum voltage is 141 V, and the ripple content is 0%. In the case of the current waveform shown by the alternate long and short dash line B, the load current is 0.25 A, the instantaneous minimum voltage is 40 V, and the ripple content is 90%. In the case of the current waveform shown by the solid line C, the load current is 0.35 A, the instantaneous minimum voltage is 0 V, and the ripple content is 141%. In the current of 0.35 A or more, neither the instantaneous minimum voltage nor the ripple content is changed.

  In the motor drive device according to the first embodiment of the present invention, the actual use range is assumed to be a load current of 0.25 A to 1.3 A. In the actual use range, a small-capacitance capacitor 3 is selected such that the ripple content is always 90% or more.

  In the first embodiment, as described above, the position cannot be detected at 50 V or less, and as a result, a portion where the position cannot be detected in any actual use range is included.

  Next, the operation in FIG. 1 will be described in more detail with reference to FIGS. FIG. 4 is a flowchart showing the operation of the inverter control unit of the motor drive device according to the first embodiment.

  First, in STEP 1, the voltage detection means 22 detects the DC voltage Vdc. The DC voltage Vdc here is the voltage across the capacitor 3. Next, in STEP2, the voltage is compared with a predetermined value 50V at which the position cannot be detected. If it is less than 50V, the process proceeds to STEP3.

  In STEP 3, the switching means 15 selects and switches the position estimation means 13. The position estimation means 13 determines whether or not a certain time has elapsed since the previous change in the position detection signal, as shown in STEP 4. This fixed time is a time determined in advance by position detection, and the time varies depending on the rotational speed.

  If the fixed time has not passed, the process passes and completes as it is, and if the fixed time has passed, the process proceeds to STEP 5 and the switching element of the inverter 5 is switched by the commutation means 16 assuming that commutation, that is, position detection has been performed. Perform the action.

  In STEP 2, the voltage is compared with a predetermined value 50V at which the position cannot be detected. If it is 50V or more, the process proceeds to STEP 6. In STEP 6, the switching means 24 selects and switches the position detection means 12. The position detection means 12 determines whether or not the position detection signal has changed its state from the previous change, as shown in STEP 7.

  If the state has not changed in STEP 7, the process passes and completes as it is. If the state has changed, the process proceeds to STEP 8, and the switching element of the inverter 5 is switched by the commutation means 16 as having performed commutation, that is, position detection. Perform the action.

  By repeating these operations within a predetermined time, the voltage detection means 14 can always detect the state of the DC voltage, and the signal between the position detection means 12 and the position estimation means 13 can be switched by the switching means 15 according to the state. The commutation operation can be performed even in a state where the position detection with a low DC voltage cannot be performed, and the operation can be continued.

  The waveforms when the operation described above is performed will be further described with reference to FIGS.

  FIG. 5 is a timing chart showing waveforms of respective parts of the motor drive device according to the first embodiment. In FIG. 5, (A) is a DC voltage, which is the voltage across the capacitor 3. (B) is voltage detection, which is the output of the voltage detection means 14. The voltage detection means 14 outputs a result obtained by comparing the direct current voltage of (A) with a predetermined voltage (50 V in the first embodiment). If the voltage detection means 14 is 50 V or more, the High level signal is output, and if it is less than 50 V, the Low level signal is output. Is output. FIG. 5 shows a case where the DC voltage is 50 V or less at times T6 and T7.

  (C) is position detection, and shows the output of the position detection means 12. Moreover, (D) is position estimation and shows the output of the position estimation means 13. When the DC voltage is 50 V or more, position detection is possible, and position detection can be performed in a normal state during the time periods T1 to T5 and T8 to T12 in FIG.

  On the other hand, at time T6 and T7 in FIG. 5, since the DC voltage is less than 50V, the position detection signal from the position detection means 12 does not come out. Or, even if it comes out, there is a high possibility that something that causes a malfunction that does not match timing at all will occur.

  Therefore, the signal of the position estimation means 13 is used for commutation at times T6 and T7. The position estimation means measures the time from the previous commutation timing T5, and performs commutation at the timing of time T6 when a predetermined time has elapsed. Similarly, at time T7, commutation is performed after a predetermined time has elapsed from time T6. The predetermined time here is a predetermined time by measuring a time during which the position can be normally detected, for example, a time between time T4 and T5.

  As described above, the switching means 15 selects and outputs the output of the position detection means 12 at times T1 to T5 and times T8 to T12. At times T6 and T7, the switching means 15 selects and outputs the output of the position estimating means 13.

  The output of the switching means 15 is input to the commutation means 16, and the commutation means 16 turns on / off the six switching elements of the inverter 5 as shown in (E) to (J) of FIG. In FIG. 5, the High level is ON and the Low level is OFF.

  As an example of an output voltage waveform of the inverter 5, FIG. The maximum output voltage is regulated by the DC voltage, and the envelope of the U-phase voltage (shown by a broken line) matches the DC voltage of (A). As described above, since the duty of PWM control is changed according to the voltage level of the DC voltage, as shown in FIG. 5 (K), the duty is increased at a low voltage (for example, between time T5 and T6), and the voltage At high points (for example, between times T11 and T12), the duty is lowered. This prevents current instability due to voltage fluctuations.

  The motor driving when using a small-capacitance capacitor in the rectifier circuit has been described above. Hereinafter, the operation or stop instruction of the compressor will be described with reference to FIGS. 1, 6, and 7. FIG. 6 is a flowchart showing the operation of the control means of the motor drive device according to the first embodiment, and FIG. 7 is a flowchart showing the operation of the inverter control unit of the motor drive device according to the first embodiment.

  First, the operation of the control means shown in FIG. 6 will be described. In the TEP 101, the electrical information from the thermistor 18 is A / D converted to obtain temperature information. Then, the rotational speed of the motor is determined from the temperature information acquired in STEP102.

  In STEP 103, it is determined whether the rotation speed of the motor determined in STEP 102 is other than 0 r / s (that is, motor stop). If it is not 0 r / s, it is determined in STEP 104 whether the motor is currently stopped.

  If the motor is stopped, the current power state of the inverter circuit is determined in STEP 105. If the power is shut off, in STEP 106, the inverter power switch 22 is turned on by the switch driving means 23 to supply power to the inverter circuit.

  If power is supplied to the inverter in STEP 105, the process proceeds to STEP 108 if a standby completion response from the inverter control unit is not acquired in STEP 107.

  In STEP 108, if the number of inquiries as to whether or not standby to the inverter unit has been completed is within a prescribed number (for example, 5 times), in STEP 109, an inquiry signal is sent to the inverter control unit as to whether or not standby has been completed. The data is output to the means 20 and transmitted to the inverter control unit via the second communication means 21 and the number of inquiries is counted.

  If the predetermined number of times has been reached in STEP 108, the power to the inverter circuit is shut off by the inverter power switch 22 by the switch driving means 23 in STEP 110. In STEP 111, the power-off flag state at the time of abnormality is checked. If the flag is not set, it is set to 1 in STEP 112. If it is set, the display means 24 warns that the inverter circuit is abnormal in STEP 113. indicate.

  Further, when there is a standby completion response from the inverter control unit in STEP 107, the motor rotational speed command value determined in STEP 114 is output to the first communication unit 20, and is transmitted to the inverter control unit via the second communication unit 21. In step 115, the inquiry counter and the power shut-off flag when the inverter is abnormal are cleared to zero.

  If the motor is being driven in STEP 104, the motor rotation speed command value determined in STEP 116 is output to the first communication means 20 and transmitted to the inverter control unit via the second communication means 21.

  If the rotational speed of the motor determined in STEP 103 is 0 r / s (that is, a stop command), it is confirmed in STEP 117 whether the motor is currently being driven. If the motor is being driven, 0 r / s ( Stop) command is output to the first communication means 20 and transmitted to the inverter control unit via the second communication means 21. When the motor is stopped in STEP 117, the switch drive means 23 cuts off the power to the inverter circuit by the inverter power switch 22.

  Next, the operation of the inverter control unit shown in FIG. 7 will be described. First, when power is supplied, initialization is performed in STEP 202, and an inquiry as to whether or not standby is completed is waited from the control unit in STEP 202.

  When an inquiry is made, the standby completion data is output to the second communication means 21 and transmitted to the control means via the first communication means 20. In step 204, the rotational speed to be driven is received. In STEP 205, the motor is driven at the command rotational speed according to the flowchart shown in FIG.

  Since the motor drive device of the present invention cuts off the power supply to the inverter while the motor is stopped, the power consumption of the motor drive device can be reduced, and the smoothing circuit uses a very small capacitor. Therefore, there is no influence of the inrush current due to the charging of the capacitor when the power is turned on again, and the harmonic current can be eliminated, so that the circuit can be reduced in size and cost. Therefore, in a device driven by a motor by an inverter, it can be easily applied to a device in which the motor repeats operation and stop depending on the switch input and the temperature state with the main power turned on.

1 is a block diagram of a motor drive device according to Embodiment 1 of the present invention. Timing chart showing voltage waveform of capacitor of motor drive device in same embodiment Characteristic diagram showing load current and instantaneous minimum voltage / ripple content of motor drive device in the same embodiment The flowchart which shows operation | movement of the inverter control part of the motor drive device in the embodiment Timing chart showing waveforms of respective parts of the motor drive device in the same embodiment The flowchart which shows operation | movement of the control means of the motor drive device in the embodiment The flowchart which shows operation | movement of the inverter control part of the motor drive device in the embodiment Block diagram of a conventional motor drive device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power supply 4 Rectifier circuit 5 Inverter 6 Motor 8 Compressor 13 Position detection means 17 Inverter control part 19 Control means 20 1st communication means 21 2nd communication means 22 Inverter power switch 24 Display means 29 Filter circuit

Claims (8)

  AC power source, a rectifier circuit having a small-capacitance capacitor with the AC power source as an input, an inverter connected to the rectifier circuit, a motor driven by the inverter, an inverter control unit for controlling the inverter, and the motor Position detecting means for detecting the position of the motor and outputting it to the inverter control section; control means for determining the command rotational speed of the motor and outputting it to the inverter control section; and a power supply to the inverter operated by the control means An inverter power switch for supplying or stopping the power supply, and when the rotational speed determined by the control means is stopped, the control means operates the inverter power switch to shut off the power supply of the inverter A motor drive device.   A first communication means for transmitting the rotational speed of the motor determined by the control means; and a second communication means for receiving a signal from the first communication means and outputting a command rotational speed to the inverter control unit. When driving the motor from a state where the motor is stopped and the inverter is powered off, the control means operates the inverter power switch to supply power to the inverter, and then the predetermined time After the elapse, the command rotational speed of the motor determined by the control means is sent to the inverter control unit via the first communication means and the second communication means, and the motor is driven at the command rotational speed. The motor driving apparatus according to claim 1.   The inverter control unit notifies the control unit that the motor can be driven via the second communication unit and the first communication unit, and the control unit is in a state where the inverter control unit can drive the motor. The motor drive device according to claim 1, wherein after confirming this, the determined command rotational speed of the motor is transmitted to the inverter control unit.   After supplying power to the inverter to drive the motor, the control means determines that there is no response from the inverter control unit even after a predetermined time has elapsed. The motor drive device according to any one of claims 1 to 3, wherein power is supplied.   5. The motor according to claim 1, further comprising a display unit configured to display a driving state of the motor, wherein the control unit displays a warning on the display unit when an abnormality in driving the motor is detected. Drive device.   It has a filter circuit for preventing noise generated from the inverter from flowing out to the commercial power source and preventing noise inflow from the commercial power source, and the filter circuit is directly connected to the commercial power source. The motor drive apparatus as described in any one of Claims 1-5.   The motor drive device according to any one of claims 1 to 6, wherein the motor is a brushless DC motor having a permanent magnet in a rotor.   The motor driving apparatus according to any one of claims 1 to 7, wherein the motor drives a compressor.

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