JP2011010432A - Motor drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem wherein positions cannot be detected and drive cannot be performed stably due to voltage drop close to 0V when the capacitance of a smoothing capacitor is reduced for miniaturization.SOLUTION: When a voltage decision means 114 determines that a pulsating bus voltage drops lower than a preset threshold, a control means 114 of controlling a voltage to be applied to a motor 106 from an inverter 105 reduces an output to the motor 106 until the motor 106 enters a regenerative state, thus preventing the voltage between DC buses from dropping close to 0 V even if the capacitance of the capacitor 103 is reduced extremely and detecting positions, thereby performing stable drive.

Description

  The present invention relates to a drive device in which the capacity of a smoothing capacitor constituting a direct-current power supply unit of a brushless DC motor used in a refrigerating and air-conditioning system such as a refrigerator and an air conditioner and other control devices such as a vacuum cleaner is reduced.

  In general, a driving device for a brushless DC motor mounted on a compressor or the like in a conventional refrigeration and air conditioning system generally includes a rectifier circuit having a sufficiently large smoothing capacitor, an inverter, and an induced voltage or a motor current without a position detection sensor. It was driven by detecting the position. This is because it was extremely difficult to attach the position sensor in a high-temperature atmosphere such as a compressor, a refrigerant atmosphere, or an oil atmosphere.

  In recent years, in order to reduce the size of this drive device, efforts have been made to significantly reduce the capacity of the smoothing capacitor of the rectifier circuit (see, for example, Patent Document 1). This conventional brushless DC motor drive device will be described with reference to the drawings.

  FIG. 6 is a block diagram of a conventional brushless DC motor driving apparatus.

  In FIG. 6, a single-phase AC power source 1 is connected to the input of a diode full-wave rectifier circuit 2, and the output is connected to a small capacitor 16 for smoothing. The small-capacitance capacitor 16 is a conventional capacitor having a capacity of about 1/100.

  The PWM (pulse width modulation) inverter 4 has six switching elements (including diodes in the reverse direction) connected in a three-phase bridge. The input is connected to both ends of a small-capacitance capacitor 16.

  The brushless DC motor 5 provided with the three-phase winding is connected to the output of the PWM inverter 4 and is driven thereby.

  The control circuit 17 receives the information such as the voltage v of the single-phase AC power supply 1, the DC part current idc, the output currents ia, ib, ic of the PWM inverter 4, and the position information θ from the position detection sensor 18 as an optimum drive. The gate of the PWM inverter 4 is driven so that

JP 2002-51589 A

  However, the above-described conventional configuration has a problem that it is difficult to apply to a device such as a compressor that is difficult to attach a sensor.

  In addition, a method for detecting the induced voltage and motor current without using a sensor to drive the inverter is generally known. However, when a small-capacitance capacitor is used, if the bus voltage pulsates and drops, the induced voltage For example, the position cannot be accurately detected, and the position cannot be accurately detected. For example, a large current flows when the position shifts, and the position stops in the worst case.

  The present invention solves the above-mentioned conventional problems, and it is difficult to attach a sensor for obtaining rotational position information of a brushless DC motor, and stable operation can be performed even if a large pulsation appears in the bus voltage. An object of the present invention is to provide a brushless DC motor drive device.

  In order to solve the above-described conventional problems, the motor driving device of the present invention detects the voltage between the DC buses and reduces the output to the motor when the voltage falls below a predetermined voltage, thereby reducing the voltage between the DC buses. Since it does not drop to near 0V and the position of the motor can be detected from the induced voltage, stable driving can be performed.

  The motor driving device of the present invention can detect the position even if the capacity of the smoothing capacitor is extremely small, and can drive the motor stably.

The block diagram which shows the electric circuit structure of the drive device of the motor in Embodiment 1 of this invention. Timing diagram showing the voltage waveform between the DC buses in the motor drive Timing diagram showing the voltage waveform when the duty width is changed by the voltage threshold in the motor drive device Current path diagram showing current flow during normal operation in the motor drive Current path diagram showing current flow when voltage drops in the motor drive The block diagram which shows the electric circuit structure of the drive device of the motor which is a prior art example

  The invention according to claim 1 is an AC power supply, a rectifier circuit that rectifies AC input from the AC power supply into DC, and an output voltage from the rectifier circuit pulsates at a frequency twice that of the AC power supply. Smoothing means that determines the value of the capacitor for which the value is set, an inverter that converts direct current obtained from the rectifier circuit into alternating current, an alternating current obtained from the inverter as an input, a motor that drives a load, and induction by the motor A position detection means for detecting the position of the motor from the generated voltage, a voltage determination means for determining whether or not the voltage between the pulsating DC buses has dropped below a predetermined threshold voltage, and the voltage determination means When the determined voltage is higher than the threshold value, an energization pattern corresponding to the position of the motor detected by the position detecting means is output, and the rotation speed during one rotation of the motor Given the duty to be constant to the inverter, when the voltage lower than the threshold value is obtained by a control means for reducing the duty width to said motor is regenerative state.

  By adopting such a configuration, the voltage between the DC buses does not drop to near 0V, and the position can be detected from the induced voltage even if the capacity of the smoothing capacitor is extremely small, and stable driving can be performed. it can.

  According to a second aspect of the present invention, the smoothing means of the first aspect of the present invention includes a capacitor and a reactor, and a resonance frequency required by the capacitor and the reactor is 40 times or more of an AC power supply frequency. By setting, it is possible to suppress the harmonic component of the AC power supply current and to improve the power supply harmonic characteristics of the input current to the rectifier.

The invention described in claim 3 is the compressor according to any one of claims 1 and 2, wherein the load is a compression mechanism of the compressor. Thus, the compressor can be stably driven by a small-capacitance capacitor, and as a result, the drive device can be significantly reduced in size.

  The invention according to claim 4 is the reciprocating compressor used as the compressor of the invention according to claim 3, whereby the reciprocating compressor uses the characteristic that the inertia is large. Therefore, even when the DC bus voltage drops, the speed fluctuation is small and more stable driving can be performed.

  According to a fifth aspect of the present invention, the compressor according to the third aspect of the present invention is provided with a refrigeration cycle comprising a condenser, a decompressor, an evaporator, etc., and constituting a refrigeration air conditioning system. It is what was used.

  By adopting such a configuration, it is possible to employ a small driving device realized by a small-capacitance capacitor, and it is possible to realize a refrigeration air conditioning system that is smaller than previously considered. When this is applied to a storage device such as a refrigerator, a large food storage capacity can be secured, and the air conditioner can be miniaturized.

  According to a sixth aspect of the present invention, the refrigerant gas compressed by the compressor according to any one of the third to fifth aspects is R600a, which compensates for a decrease in refrigeration capacity. Therefore, the cylinder volume of the compressor can be increased, and as a result, the compressor can have a larger inertia, and more stable start-up and acceleration can be performed, and the environmental load using R600a as a refrigerant gas can be increased. A small and inexpensive compressor can be provided.

  According to a seventh aspect of the present invention, the load according to the first or second aspect of the present invention is a washing mechanism of an electric washing machine. As a result, the capacity of the washing and dewatering tank can be increased with the same external dimensions as those of the conventional electric washing machine.

  The invention according to claim 8 uses the load of the invention according to claim 1 or 2 as an agitation mechanism of an electric dryer for agitating and drying clothes and the like. Along with the miniaturization of the motor drive device, it is possible to increase the drum capacity with the same external dimensions as the conventional electric dryer.

  According to a ninth aspect of the present invention, the load according to the first or second aspect of the present invention is used as a blower mechanism of a blower device, thereby reducing the size of the motor drive device. As a result, it is possible to achieve a reduction in size and weight as compared with a conventional blower machine, and to provide a highly portable blower.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments.

(Embodiment 1)
FIG. 1 is a block diagram of a motor driving apparatus according to Embodiment 1 of the present invention.
In FIG. 1, an AC power supply 101 is a general commercial AC power supply having a voltage of 100 [V] and a frequency of 50 [Hz] or 60 [Hz] in Japan. As is well known, the rectifier circuit 102 is a bridge connection of four diodes.

  The smoothing means 103 sets the value of the capacitor so that the output voltage from the high-frequency removing means 104 constituted by a common mode filter and the output voltage from the rectifier circuit 102 pulsates substantially at a frequency approximately twice the AC power supply frequency.

The smoothing means 3 has a small-capacity film capacitor set so that the resonance frequency is 40 times or more of the AC power supply frequency, and a reactor for lowering the peak value of the inrush charging / discharging current to the capacitor. Yes.

  Note that the reactor constituting the smoothing means 3 is inserted between the AC power supply 101 and the film capacitor constituting the smoothing means 3, and therefore may be either before or after the rectifier circuit 102. Further, the reactor takes into consideration a composite component with the reactance component of the common mode filter constituting the high-frequency removing means 104.

  The inverter 105 is composed of a plurality of semiconductor switching elements that convert the output voltage from the smoothing means 103 into a desired voltage value and frequency for driving the motor 106.

  The motor 106 is a brushless DC motor this time, and is driven by the three-phase output of the inverter 105. The stator of the motor 106 is provided with a three-phase star-connected winding. This winding method may be concentrated winding or distributed winding. A permanent magnet is disposed on the rotor. 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.

  A compression element 107 connected to the rotor shaft of the motor 106 draws in refrigerant gas, compresses it, and discharges it. The motor 106 and the compression element 107 are accommodated in the same hermetic container to constitute the compressor 108. The compression method (mechanism form) of the compressor 108 may be anything such as a rotary or a scroll, but this time it is a reciprocating type. The reciprocating type has particularly large inertia and is difficult to reduce the rotational speed even when the voltage drops. The reciprocating type can be operated more smoothly with a small capacity capacitor.

  The refrigerant gas may be anything such as R134a, but R600a is adopted in the first embodiment. The R600a has a lower refrigeration capacity than the R134a, and the cylinder volume of the compression element 107 is increased to compensate for a decrease in the refrigeration capacity. As a result, the compressor 108 has a large inertia. As a result, even when the voltage drops, the motor 106 rotates due to the inertia, so the speed is unlikely to drop, and stable operation is possible even when the capacitor 103 is operated with a small capacity.

  The discharge gas compressed by the compressor 108 constitutes a refrigeration air conditioning system that returns to the suction of the compressor 108 through the condenser 109, the decompressor 110, and the evaporator 111. At this time, the condenser 109 dissipates heat and the evaporator 111 absorbs heat, so that cooling and heating can be performed. If necessary, a blower or the like may be used for the condenser 109 or the evaporator 111 to further promote heat exchange.

The position detector 112 detects the rotational position of the rotor in the motor 106 from the induced voltage or motor current of the motor 106. In the first embodiment, a method for detecting the rotational position of the rotor from the induced voltage will be described. Since the inverter 105 is a 120-degree conduction type rectangular wave drive, among the three phases U, V, and W, phases that are not always energized are generated in a predetermined order. The zero cross point of the induced voltage generated in the non-energized phase is detected, and the rotational position of the rotor is detected. The detected rotor position is output to the control means 113. The voltage determination means 114 detects the voltage between the DC buses, determines whether the detected voltage is higher or lower than a preset threshold value, and determines the determination result. Output to the control means 113.

  The control means 113 uses PWM control as a method for controlling the voltage applied to the motor 106. From the output of the position detection means 112, the calculation of the current flowing in each phase of the motor, and the duty from the output of the voltage determination means 114. Control the width.

The operation and operation of the motor driving apparatus configured as described above will be described below. First, voltage waveforms at both ends of the capacitor constituting the smoothing means 103 will be described with reference to FIGS. FIG. 2 is a timing chart showing a voltage waveform between the DC buses in the first embodiment.

  In FIG. 2, the vertical axis represents voltage, and the horizontal axis represents time.

  Waveform A is a state when the load current is very small (almost no current flows), and the charge of the capacitor constituting the smoothing means 103 is hardly used, and the voltage is hardly lowered. However, the load current here is the output current of the rectifier circuit 102, that is, the input current to the inverter 105. The maximum value of the voltage after rectification is 141 [V] and the minimum value is 141 [V], so the voltage difference is almost zero.

  Next, as the load current is increased, the charge of the capacitor constituting the smoothing means 103 is used, and the minimum voltage is instantaneously lowered as shown by the waveform B.

  When the load current is further increased, almost no charge charge is stored in the capacitor constituting the smoothing means 103, and as shown by the waveform C, the instantaneous minimum voltage decreases to almost 0 [V].

  In this way, when the small-capacitance capacitor 103 has a small capacitance, when the load current is extracted, the input AC power source 101 is almost completely rectified without being almost smoothed.

In order to suppress the harmonic component of the AC power supply current and comply with the IEC standard, the resonance frequency f _LC (LC resonance frequency) of the small-capacitance capacitor and the small-capacity reactor becomes larger than 40 times the AC power supply frequency f _s. Thus, the combination of a small capacitor and a small reactor is determined.

Here, when the capacitance of the small-capacitance capacitor is C [F] and the inductance value of the small-capacity reactor is L [H], the LC resonance frequency f _LC is expressed as shown in Equation 1.

That is, the combination of the small capacitor and the small reactor is determined so as to satisfy f _LC > 40 f _s . (Because the IEC standard specifies the 40th harmonic in the harmonic component of the AC power supply current)
As described above, by determining the combination of the small-capacitance capacitor and the small-capacity reactor, it is possible to suppress the harmonic component of the AC power supply current and comply with the IEC standard.

  Next, the operation when the voltage between the DC buses is near the peak will be described. The control means 113 controls the PWM duty width so that the current desired to flow through the motor 106 flows. At this time, since the voltage between the DC buses is sufficiently high, the position detector 112 can detect the position of the motor 106 from the induced voltage.

Next, the case where the voltage between the DC buses decreases from the vicinity of the peak and enters a state lower than the threshold value preset by the voltage determination means 114 will be described with reference to FIG. Assuming that the threshold value of the voltage determination unit 114 is 8V and the voltage at which no current flows to the current detection unit is 8V, the threshold value of the voltage determination unit 115 is 27V. When the PWM carrier period is 5 kHz, the maximum amount of change in the voltage of the three carriers is 27 V, so that the control of Embodiment 1 can be activated before the voltage drops below 8 V. Here, the voltage at which current does not flow to the current detection means is 8 V, but this value varies depending on each configuration.

  First, since the voltage between the DC buses has changed from a state higher than the threshold of 27 V to a lower state, the voltage determination unit 115 changes the output to the control unit 114 from “high” to “low”. When the control means 113 continues to determine the duty width so that the voltage applied to the motor 106 can be maintained at this time, the voltage decreases to near 0V as shown by the waveform A, and the position detection means 112 can observe the induced voltage. Cannot detect the position.

  On the other hand, the control means 113 receives information that the voltage is lower than the threshold value, so that it does not determine the duty width necessary for driving the motor 106 but tries to output it to maintain the speed of the motor 106. Outputs a duty width that is half the duty width. If the regenerative state is not reached, the output is stopped in the next carrier, and the motor 106 is operated in the regenerative state.

  As a result, the motor 104 is in a regenerative state, and the voltage between the DC buses rises as shown by the waveform B, and the position can be detected by the position detecting means 112 without being lowered to around 0 V as shown by the waveform A.

  By reducing the duty, the supplied energy is reduced and the phase is shifted to the lag side. Since the induced voltage of the motor 104 operating in the weak magnetic flux state is higher than the bus voltage, the terminal voltage increases. As the duty width is narrowed, the regenerative energy increases and the voltage rise between the DC buses increases. That is, by stopping the output, it is possible to reliably observe the induced voltage and detect the position.

  In addition, the period during which the duty width is reduced is set in advance, and the threshold voltage is set to 3 carriers of 27 V this time, so that it is doubled to 6 carriers.

  Details of the current flow will be described with reference to FIGS. 4 and 5 are current path diagrams showing details of components of the inverter 105 and current flow.

  The inverter 105 is constituted by a three-phase bridge connection of six switches 105a to 105f and diodes 105g to 105l connected in the opposite direction to the switches 105a to 105f. FIG. 4 shows a current path when a current is flowing in accordance with the phase of the normal motor 106. The switch 105a on the U phase is switching the PWM output, and the switch 105e below the V phase is ON. State. At this time, the current flows from the positive side of the DC bus, passes through the switch 105a on the U phase, passes through the motor 106, passes through the switch 105e under the V phase, and flows to the negative side of the DC bus. Become.

  Here, when the duty is decreased, the voltage between the motor 104 and the DC bus is reversed, and current flows through the diode 105g under the U phase and the diode 105h under the V phase by the inductance of the motor 104 as shown in FIG. It will be.

  In the first embodiment, the duty width is decreased step by step when the voltage is lowered. However, the duty to be decreased may be determined in advance according to each state.

  As described above, in the first embodiment, the rectifier circuit 102 that rectifies alternating current input from the alternating current power supply 101 into direct current, and the output voltage from the rectifier circuit 102 pulsates at twice the frequency of the alternating current power supply 101. Smoothing means 103 that has determined the value of the capacitor having such a value, inverter 105 that converts the direct current obtained from rectifier circuit 102 into alternating current, motor 106 that receives the alternating current obtained from inverter 105 and drives the load, It is determined by position detection means 112 for detecting the position of the motor 106, voltage determination means 114 for determining whether or not the voltage between the pulsating DC buses has dropped below a predetermined threshold voltage, and voltage determination means 114. When the detected voltage is higher than the threshold value, an energization pattern corresponding to the position of the motor detected by the position detecting means 112 is output and rotated once. Given duty rotational speed of the constant to the inverter 105, when the voltage lower than the threshold value is obtained by a control means for reducing the duty width until the motor 106 is regenerated state.

  By adopting such a configuration, the voltage between the DC buses is not reduced to near 0 V, and the position can be detected from the induced voltage even if the capacitance of the capacitor constituting the smoothing circuit is extremely small, and stable driving is achieved. It can be carried out.

  In the present embodiment, the smoothing means 103 is composed of a capacitor and a reactor, and the resonance frequency required by the capacitor and the reactor is set to be 40 times or more the frequency of the AC power source 101, so that the AC power source The harmonic component of the current 101 can be suppressed, and high performance of the power supply harmonic characteristic of the input current to the rectifier circuit 102 can be realized.

  Further, in this embodiment, the load of the motor 106 is the compression mechanism of the compressor 108, so that the compressor can be stably driven by a small-capacitance capacitor in an application where a position detection sensor cannot be attached. As a result, the drive device can be significantly reduced in size.

  In the present embodiment, the compressor 108 includes a condenser 109, a decompressor 110, an evaporator 111, and the like, and is used in a refrigeration cycle that constitutes a refrigeration air conditioning system.

  By adopting such a configuration, it is possible to employ a small driving device realized by a small-capacitance capacitor, and it is possible to realize a refrigeration air conditioning system that is smaller than previously considered. When this is applied to a storage device such as a refrigerator, a large food storage capacity can be secured, and the air conditioner can be miniaturized.

  Further, in the present embodiment, the refrigerant gas compressed by the compressor is R600a, and by doing so, the cylinder volume of the compressor can be increased to compensate for the decrease in the refrigerating capacity. A large inertia can be given to the compressor, and more stable start-up and acceleration can be performed, and an inexpensive compressor with a small environmental load using R600a as a refrigerant gas can be provided.

  Further, the load of the motor 106 is a washing mechanism (not shown) of the electric washing machine, and as a result, due to the downsizing of the motor driving device, the outer dimensions of the motor 106 are the same as those of the conventional electric washing machine. Large capacity of washing and dewatering tank can be achieved.

  In addition, the load of the motor 106 is a blower mechanism (not shown) of the blower, and as a result, the motor drive device is downsized and reduced in size compared to the conventional blower machine. Weight reduction can be achieved and a highly portable air blower can be provided.

In addition, the load of the motor 106 is a dust suction mechanism (not shown) of the electric vacuum cleaner, which makes it possible to reduce the size and weight of the vacuum cleaner due to the miniaturization of the motor drive device. Further, it is possible to provide an electric vacuum cleaner that is more portable and easy for the user to handle.

  As described above, the motor drive device according to the present invention can provide a stable current supply while maintaining efficiency without using a position detection sensor even when there is a large ripple voltage with a smoothing capacitor greatly reduced in capacity. AV equipment that can be driven stably without stopping, and requires a small motor drive device as well as a compressor, an electric washing machine, an electric dryer, and an electric vacuum cleaner (particularly It can also be widely used for small devices.

DESCRIPTION OF SYMBOLS 101 AC power supply 102 Rectifier circuit 103 Smoothing means 104 High frequency removal means 105 Inverter 106 Motor 107 Compression element 108 Compressor 109 Condenser 110 Decompressor 111 Evaporator 112 Position detection means 113 Control means 114 Voltage determination means

Claims (9)

Determine the value of the AC power supply, the rectifier circuit that rectifies the alternating current input from the alternating current power supply into direct current, and the capacitor that is set so that the output voltage from the rectifier circuit pulsates at twice the frequency of the alternating current power supply. Smoothing means, an inverter for converting direct current obtained from the rectifier circuit into alternating current, an alternating current obtained from the inverter as an input, a motor for driving a load, and a position of the motor from a voltage induced by the motor. Position detecting means for detecting, voltage determining means for determining whether or not the voltage between the pulsating DC bus is lower than a predetermined threshold voltage, and the voltage determined by the voltage determining means is higher than the threshold When the duty is output, the energization pattern according to the position of the motor detected by the position detection means is output, and the rotation speed during one rotation of the motor is constant. The given to the inverter, when the voltage lower than the threshold motor drive apparatus provided with a control means for reducing the duty width to said motor is regenerative state. 2. The inverter device according to claim 1, wherein the smoothing means includes a capacitor and a reactor, and a resonance frequency required by the capacitor and the reactor is set to be 40 times or more of an AC power supply frequency. The motor driving apparatus according to claim 1, wherein the load is a compression mechanism of a compressor. The motor driving device according to claim 3, wherein the compressor is a reciprocating compressor. The motor driving device according to any one of claims 3 and 4, wherein the compressor includes a condenser, a decompressor, an evaporator, and the like, and is used in a refrigeration cycle constituting a refrigeration air conditioning system. The motor driving device according to any one of claims 3 to 5, wherein the refrigerant gas compressed by the compressor is R600a. The motor driving device according to claim 1, wherein the load is a washing mechanism of an electric washing machine. The motor driving device according to claim 1, wherein the load is a stirring mechanism of an electric dryer that stirs and dries clothes and the like. The motor drive device according to claim 1, wherein the load is a blower mechanism of a blower.