JP2008289310A - Motor drive and refrigerator using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor drive improving efficiency, speed and torque. <P>SOLUTION: The motor drive is provided with a brushless DC motor 5 composed of a rotor having a permanent magnet and a stator having three phase winding, an inverter 3 supplying power to three phase winding, a first waveform generating part 15 outputting a rectangular wave whose conduction angle is 120 to 150 degrees or a waveform conforming thereto, a second waveform generating part 17 outputting the rectangular wave whose conduction angle is 130 to 180 degrees or a waveform conforming thereto, and a switching determination part 18 selecting output of the first waveform generating part 15 at a prescribed speed or lower and output of the second waveform generating part 17 at a speed higher than the prescribed speed. When a drive mode transition from the second waveform generating part 17 to the first waveform generating part 15, the conduction angle is set to be not more than 150 degrees. Thus, stable mode transition is achieved. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a motor drive device that drives and controls a brushless DC motor using an inverter, and a refrigerator using the motor drive device.

  Conventionally, this type of motor drive device realizes high-speed drive and high-efficiency drive by switching the waveform generation method between when driving a brushless DC motor at low speed and when driving at high speed. (For example, refer to Patent Document 1).

  FIG. 4 shows a conventional motor driving apparatus. As shown in FIG. 4, a conventional motor driving apparatus includes a rectifying / smoothing circuit 202 that converts an AC power supply 201 into an input DC voltage, and an inverter 203 that converts an output of the rectifying / smoothing circuit as an input into pseudo AC power having a predetermined frequency. , A drive unit 204 for controlling on / off of the switching element of the inverter 203, a brushless DC motor 205 driven by the inverter 203, a position detecting unit 206 for detecting the position of the rotor of the brushless DC motor 205, and a position detecting unit 206. The first waveform generator 207 that determines the duty and the commutation timing by feedback control based on the position information of the brushless DC motor from the generator and generates the output waveform of the inverter 203, and the commutation by open loop control with a constant duty By changing the timing, The second waveform generator 208 that generates the output waveform of the motor 203, the rotation speed detector 209 that detects the driving speed of the brushless DC motor 5 from the output signal of the position detector 206, and the speed detected by the rotation speed detector 209. A switching determination unit 210 that switches between the first waveform generation unit 207 and the second waveform generation unit 208 is provided.

  In the motor driving apparatus configured as described above, when the brushless DC motor 205 is driven at a relatively low load and low speed, the switching determination unit 210 selects the first waveform generation unit 207 and performs high-efficiency brushless DC by feedback control. The motor 205 is driven. On the other hand, when the load is large in driving by the first waveform generator 207, or when the duty reaches 100% by driving at high speed, further high speed driving or high load driving becomes impossible.

Therefore, in the conventional motor driving device, switching to driving by the second waveform generator 208 and the brushless DC motor 205 is performed in an open loop operation (synchronous operation), thereby ensuring high load and high speed driving performance.
JP 2004-282911 A

  However, in the above-described conventional configuration, when switching from feedback control (driving by the first waveform generator 207) while detecting the position of the rotor to open-loop driving (driving by the second waveform generator 208), the waveform Although smooth switching is possible by making the commutation timings before and after switching of the generators the same, when moving from the second waveform generator 208 to the driving by the first waveform generator 207, the position of the rotor Since it is not known, when a deviation between the applied voltage phase and the motor phase occurs, there are problems such as motor step-out stop and current protection due to overcurrent becoming easier to operate.

  The present invention solves the above-described conventional problems, and improves the practicality of the conventional motor drive device by smoothly performing the drive transition by the first waveform generator and the drive by the second waveform generator. is there.

  In order to achieve the above object, the motor driving device of the present invention has an energization angle of 150 degrees or less when shifting from driving by the second waveform generator to driving by the first waveform generator.

  Thereby, the position of the rotor can be detected from the induced voltage of the brushless DC motor, and the shift to the drive by feedback control can be smoothly performed while detecting the position of the rotor.

  The motor drive device of the present invention can provide a highly practical motor drive device that realizes high efficiency, high speed, and high torque drive.

  Moreover, the refrigerating air-conditioning cycle which acquired the said effect can be provided by using the motor drive device of this invention for a cooling-air-conditioning system.

  According to a first aspect of the present invention, there is provided a motor drive device comprising: a brushless DC motor comprising a rotor having a permanent magnet and a stator having a three-phase winding; and an inverter for supplying power to the three-phase winding; A first waveform generator for outputting a rectangular wave having a conduction angle of 120 ° to 150 ° or a waveform corresponding thereto, and a second waveform generating a rectangular wave having a conduction angle of 130 ° to less than 180 ° or a waveform corresponding thereto. And a switching determination unit that selects the output of the first waveform generator at a low speed below a predetermined speed and the output of the second waveform generator at a high speed exceeding a predetermined speed, respectively, and generates the second waveform In the case of shifting from driving in the section to driving in the first waveform generating section, the energization angle is set to 150 degrees or less.

  This makes it possible to suppress step-out stop and overcurrent generation when shifting from driving at the second waveform generation unit to driving at the first waveform generation unit, and driving the motor with high efficiency, high speed, and high torque. The stable drive performance of the apparatus can be improved.

  According to a second aspect of the present invention, in addition to the first aspect of the present invention, the motor drive device detects the relative position of the rotor of the brushless DC motor from the induced voltage generated by driving the brushless DC motor. And when shifting from driving by the first waveform generator to driving by the second waveform generator, a predetermined position relative to the relative position of the rotor of the brushless DC motor detected by the position detector is provided. The conduction phase of the inverter is switched at the timing.

  As a result, when shifting from driving by the second waveform generating unit to driving by the first waveform generating unit, the voltage can be supplied to the brushless DC motor with an appropriate voltage phase with respect to the relative position of the rotor. Along with the realization of the transition of the waveform generator, further reliability can be enhanced.

  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 second waveform is obtained when the relative position of the rotor of the brushless DC motor cannot be detected by the position detecting means. The drive at the generator is not shifted to the drive at the first waveform generator (shift is prohibited).

  When the energization angle is 150 degrees or less and the zero cross of the induced voltage cannot be detected, the driving by the first waveform generation unit is in a state where the load cannot be increased, and thus the transition to the first waveform generation unit is prohibited. This prevents step-out stop and overcurrent occurrence, and can greatly improve the reliability of the motor drive device.

  According to a fourth aspect of the present invention, the brushless DC motor according to any one of the first to third aspects drives a compressor of a refrigerating and air-conditioning cycle. A refrigeration and air conditioning cycle having the effect of the invention according to any one of claims 1 to 3 can be provided.

  The invention of the refrigerator according to claim 5 uses the motor driving device according to any one of claims 1 to 4 for driving a compressor of the refrigerator.

  As a result, the power consumption of the refrigerator can be reduced, and high-speed driving in a high load state in which the inside temperature and the outside air temperature are high is also possible, thereby improving the cooling performance.

  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 apparatus according to Embodiment 1 of the present invention. In FIG. 1, an AC power source 1 is a general AC power source of AC 100 V, 50 Hz, or 60 Hz in the case of Japan. The rectifying / smoothing circuit 2 receives the AC power supply 1 as an input, converts AC to DC, and inputs it to the inverter 3. In this embodiment, voltage doubler rectification is used, but full-wave rectification may be used.

  The inverter 3 is composed of six switching elements, converts the DC power input from the rectifying and smoothing circuit 2 into AC power, and supplies the brushless DC motor 5 with power. In this embodiment, an FET is used as a switching element, but an IGBT or a bipolar transistor may be used.

  The brushless DC motor 5 includes a rotor having a permanent magnet and a stator in which three-phase winding is promoted. In the present embodiment, the brushless DC motor is connected to the compression element 6. The compression element 6 is connected to the rotor shaft of the brushless DC motor 5, sucks refrigerant gas, compresses it, and discharges it. The brushless DC motor 5 and the compression element 6 are accommodated in the same hermetic container to constitute the compressor 7.

  The discharge gas compressed by the compressor 7 constitutes a refrigeration air-conditioning system that returns to the suction of the compressor 7 through the condenser 8, the decompressor 9, and the evaporator 10. Then, since endotherm is performed, cooling and heating can be performed. In addition, a heat exchanger may be further accelerated | stimulated using a fan etc. for the condenser 8 or the evaporator 10 as needed. In the present embodiment, the refrigeration system is configured to cool the inside 11 of the refrigerator by the evaporator 10.

  The position detecting means 12 detects an induced voltage generated by the rotation of the rotor of the brushless DC motor 5 to detect the relative position of the rotor, and the output terminal voltage of the inverter 3 is determined for each PWM carrier period. The position detection unit 13 that detects the analog voltage at the frequency of the frequency and the relative position information of the brushless DC motor rotor obtained by the position detection unit 13 is correct, that is, the rotor position information is obtained by the induced voltage detection method. The position detection enable / disable determining means 14 is configured to determine whether or not the position detection is performed.

  The first waveform generation unit 15 generates a signal for driving the switch element of the inverter 3 at a conduction angle of 120 degrees or more and 150 degrees or less based on the position signal of the position detection unit 12. Further, the first waveform generator 15 performs duty control of PWM control in order to keep the rotation speed of the brushless DC motor 5 constant, and operates at an optimal duty according to the rotation position of the brushless DC motor 5. The most efficient drive is performed.

  The rotation speed detection unit 16 detects the driving speed of the brushless DC motor 5 from the output signal of the position detection means 12, and is realized by counting the output signal of the position detection means 12 for a certain time or measuring the cycle. is doing.

  The second waveform generator 17 generates a rectangular waveform having a conduction angle of less than 180 degrees from the target speed of the brushless DC motor 5. At this time, the PWM duty is constant, and operation is performed at 90% to 100%.

  The switching determination unit 18 selects a waveform for operating the inverter 3 from the waveform by the first waveform generation unit 15 and the waveform by the second waveform generation unit 17 based on the deviation between the speed detected by the rotation speed detection unit 16 and the target speed. The input is switched.

  Specifically, the brushless DC motor 5 is driven by the first waveform generator 15 at a normal time equal to or lower than a predetermined speed after the brushless DC motor 5 is started, and is driven at a high speed exceeding a predetermined speed or in a high load state. Therefore, when the target speed cannot be reached by driving with the first waveform generator 15, switching to driving with the second waveform generator 17 is performed.

  The drive unit 19 drives the switching element of the inverter 3 based on the output signal from the switching determination unit 18, and AC power is supplied to the brushless DC motor 5 by appropriate switching of the switching element, and the rotor of the brushless DC motor 5 is driven. Can be rotated.

  In the motor driving apparatus configured as described above, a transition from driving by the second waveform generator 17 to driving by the first waveform generator 15 will be described below.

  FIG. 2 is a timing chart showing the output terminal voltage of the inverter of the motor drive device of the present embodiment. 2A shows the waveform of the induced voltage generated in the stator winding due to the rotation of the rotor of the brushless DC motor 5, and FIGS. 2B and 2C show the waveform generated by the second waveform generator 17. FIG. The waveform of the terminal voltage of the inverter 3 output when the brushless DC motor 5 is driven with 150 ° energization, FIG. 6D shows the voltage waveform of the output terminal of the inverter 3 with 120 ° energization by the first waveform generator 15. Is shown.

  In FIG. 2D, the drive by the first waveform generator 15 measures the on / off timing of the switching element of the inverter 3 by feedback control while detecting the relative position of the rotor of the brushless DC motor 5. The phase relationship between the brushless DC motor 5 and the terminal voltage always remains constant (in this embodiment, the advance angle is set to 0 degree, and the terminal voltage phase and the induced voltage phase are kept in agreement. ).

  As a method for detecting the relative position of the brushless DC motor 5, the induced voltage of the brushless DC motor 5 appearing in the inverter 3 output terminal voltage (section 1d and section 2d in (d)) is the inverter 3 input voltage (that is, the output of the rectifying and smoothing circuit). Voltage) is detected as the rotor position (zero cross point) at which the induced voltage is 0V.

  On the other hand, in the driving by the second waveform generation unit 17, since an arbitrary output frequency is maintained as a synchronous motor and controlled in an open loop regardless of the rotor position (induced voltage phase) of the brushless DC motor 5, The induced voltage phase and the inverter 3 terminal voltage phase change depending on the speed and load state of the brushless DC motor 5.

  (B) shows a state in which the load state with respect to the speed is relatively large, the output terminal voltage phase is advanced by 30 degrees with respect to the induced voltage phase, and (c) shows a state in which the load with respect to the speed is relatively small. The phase of the output terminal voltage with respect to the induced voltage phase is advanced by 15 degrees.

  As described above, in the driving by the second waveform generator 17, when driving at a constant speed, the output terminal voltage phase shifts in the advance direction with respect to the induced voltage phase when the load is large (actually, it rotates to commutation). Since the child follows, the induced voltage is delayed with respect to the terminal voltage phase).

  Here, detection of the induced voltage zero cross timing for detecting the position of the rotor will be described. As described above, the relative position of the rotor detects the position where the induced voltage becomes 0V.

  The induced voltage appears in the terminal voltage (1b, 2b, 1c, 2c, 1d, and 2d in FIG. 2) when both the upper and lower switching elements of an arbitrary phase are in the off state, and the phase relationship between the induced voltage and the terminal voltage is shifted. Therefore, the portion of the induced voltage that appears differs.

  When the advance angle is 0 degree, an induced voltage of plus or minus 15 degrees (plus or minus 30 degrees for 120 degree energization shown in (d)) appears at 150 degrees energization around the zero cross of the induced voltage, but the advance angle becomes large. Accordingly, the zero cross point of the induced voltage is shifted to the left, and if the advance angle exceeds 15 degrees as shown in (c), the zero cross point of the induced voltage cannot be detected by the terminal voltage of the inverter.

  In other words, when the advance angle is 15 degrees or less, the zero cross point of the induced voltage can be detected. When the advance angle becomes 15 degrees or less in the driving by the second waveform generator 17, the relative position of the rotor This also means that the first waveform generator 15 that performs feedback control while detecting can be driven.

  Therefore, in order to smoothly drive from the driving by the second waveform generator 17 to the driving by the first waveform generator 17, it is necessary and sufficient condition that the zero cross point of the induced voltage can be detected. It is necessary to extract the position information after determining whether or not the information from the detected signal can detect the position information of the rotor.

  Here, the operation of detecting the position of the rotor by the position detecting means 12 will be described. FIG. 3 is a flowchart showing the operation of the position detecting means 12 of the present embodiment.

  First, at Step 101, the position detection unit 13 acquires the output terminal voltage of the inverter 3. In Step 102, it is determined whether or not the acquired voltage has passed the 1/2 potential point of the inverter input.

  That is, at the timing when the induced voltage rises (1b, 1c interval in FIGS. 2B and 2C), it is determined whether or not the voltage is equal to or higher than ½ voltage of the acquired inverter input, and if it is the falling timing (FIG. (2b, 2c in 2 (b), (c)) It is determined whether or not the acquired voltage is equal to or less than ½ voltage of the inverter input.

  If the inverter input does not reach the 1/2 potential, the operation is repeated, and if the inverter reaches the 1/2 voltage, the process proceeds to Step 103.

  The operation after Step 103 is the operation by the position detection possibility determination means 14 and confirms whether the difference between the terminal voltage value acquired last time and the current acquisition value is within a predetermined value. For example, assuming that the timing of p1 shown in FIG. 2B is the voltage level acquired last time, the point acquired this time is p2.

  Since the state of (b) is a state in which the advance angle is greater than 15 degrees, the zero cross timing of the induced voltage cannot be detected. Therefore, when the voltage reaches 1/2 or more of the inverter output terminal voltage at the point of p2, Deviation from the previous value becomes larger.

  In this case, the information acquired in Step 104 is determined not to be reliable as the rotor position information, and the rotor position signal cannot be acquired. Therefore, feedback control based on the position signal cannot be performed in the current load state and speed state. As a state, the driving by the second waveform generator 17 is continued, and this operation is repeated thereafter.

  In addition, when the inverter output terminal voltage value acquired at the previous step 103 is the point p3 shown in FIG. 2C, and the current acquired value is ½ of the inverter input terminal voltage (p4 in the figure) The deviation from the previous value is small (within a predetermined difference), and the process proceeds to Step 105.

  In Step 105, the detected signal from the position detector 13 is recognized as position information of the rotor. As a result, the switching speed of the switching element is determined based on the driving speed and the position information, so that overcurrent and the like can be reduced when switching from driving by the second waveform generator 17 to driving by the first waveform generator 15. It is possible to achieve a smooth and smooth operation that is suppressed.

  As described above, in the present embodiment, the brushless DC motor 5 including the rotor having the permanent magnet and the stator having the three-phase winding, the inverter 3 that supplies power to the three-phase winding, and the conduction angle are A first waveform generator 15 that outputs a rectangular wave of 120 degrees or more and 150 degrees or less or a waveform conforming thereto, and a second waveform that outputs a rectangular wave having a conduction angle of 130 degrees or more and less than 180 degrees or a waveform conforming thereto at a predetermined frequency. And a switching determination unit 18 that selects an output of the first waveform generation unit 15 at a low speed that is equal to or lower than a predetermined speed, and an output of the second waveform generation unit 17 at a high speed that exceeds the predetermined speed. When shifting from driving by the waveform generation unit 17 to driving by the first waveform generation unit 15, the driving by the second waveform generation unit 17 is changed from the driving by the second waveform generation unit 15 by setting the conduction angle to 150 degrees or less. Shift to driving When, it is possible to inhibit demineralization mediation stop or overcurrent, stable driving performance of the motor driving apparatus of high efficiency, high speed and high torque can be improved.

  Further, the present embodiment has position detecting means 12 for detecting the relative position of the rotor of the brushless DC motor 5 from the induced voltage generated by driving the brushless DC motor 5, and from the driving by the first waveform generating unit 15. When the drive by the second waveform generator 17 is shifted, the energized phase of the inverter 5 is switched at a predetermined timing with respect to the relative position of the rotor of the brushless DC motor 5 detected by the position detector 12. When moving from the drive at the second waveform generator 17 to the drive at the first waveform generator 15, the voltage can be supplied to the brushless DC motor 5 with an appropriate voltage phase with respect to the relative position of the rotor. In addition to the realization of the transition of a simple waveform generator, further reliability can be improved.

  In the present embodiment, when the relative position of the rotor of the brushless DC motor 5 cannot be obtained by the position detection unit 12, the driving from the second waveform generation unit 17 to the driving by the first waveform generation unit 15 is performed. The transition to was prohibited.

  As a result, when the energization angle is 150 degrees or less and the zero cross of the induced voltage cannot be detected, the driving by the first waveform generator 15 is in a state in which the load is not large, and therefore the first waveform generator 15 Prohibiting the transition prevents step-out stop and overcurrent, and can greatly improve the reliability of the motor drive device.

  Further, by using the brushless DC motor 5 for driving the compressor 7 of the refrigeration air conditioning cycle, it is possible to provide a refrigeration air conditioning cycle having the above effects.

  Further, by using the motor drive device for driving the compressor 7 of the refrigerator, it is possible to reduce the amount of power consumed by the refrigerator, and it is also possible to drive at high speed in a high load state where the inside temperature and the outside air temperature are high. Cooling performance can be enhanced.

  Since the motor drive device according to the present invention can provide a motor drive device with high efficiency, high speed, and high torque, such as white goods using a motor such as an air conditioner, a washing machine, and a vacuum cleaner, a DVD player, etc. It can be used in a wide range of applications using brushless DC motors such as AV equipment and industrial equipment such as hydraulic pumps.

1 is a block diagram of a motor drive device according to Embodiment 1 of the present invention. Timing chart showing the relationship between the waveform of the induced voltage generated in the stator winding of the brushless DC motor and the waveform of the output terminal voltage of the inverter in the motor drive device of the embodiment Flowchart showing the operation of the position detection means in the motor drive device of the same embodiment Block diagram of a conventional motor drive device

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 Inverter 5 Brushless DC motor 7 Compressor 12 Position detection means 15 1st waveform generation part 17 2nd waveform generation part 18 Switching determination part

Claims (5)

  A brushless DC motor including a rotor having a permanent magnet and a stator having a three-phase winding, an inverter for supplying power to the three-phase winding, a rectangular wave having a conduction angle of 120 ° to 150 ° or the like A first waveform generator for outputting a waveform, a second waveform generator for outputting a rectangular wave having a conduction angle of 130 degrees or more and less than 180 degrees or a waveform equivalent thereto, and a low speed below a predetermined speed, A switching determination unit that selects the output of the second waveform generation unit at a high speed exceeding a predetermined speed, and shifts from driving by the second waveform generation unit to driving by the first waveform generation unit; If so, a motor drive device with a conduction angle of 150 degrees or less.   It has position detecting means for detecting the relative position of the rotor of the brushless DC motor from the induced voltage generated by driving the brushless DC motor, and shifts from driving by the first waveform generating section to driving by the second waveform generating section. 2. The motor drive device according to claim 1, wherein when performing the operation, the conduction phase of the inverter is switched at a predetermined timing with respect to the relative position of the rotor of the brushless DC motor detected by the position detection unit.   3. The driving device according to claim 1, wherein when the relative position of the rotor of the brushless DC motor cannot be detected by the position detection unit, the driving by the second waveform generation unit does not shift to the driving by the first waveform generation unit. Motor drive device.   The motor driving device according to any one of claims 1 to 3, wherein the brushless DC motor drives a compressor of a refrigeration air conditioning cycle.   A refrigerator using the motor driving device according to any one of claims 1 to 4 for driving a compressor.