JP2008109722A - Motor drive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor drive arranged to operate a cooling system with the highest efficiency, by shifting the phase angle of a motor such that harmonic regulation is satisfied by reducing the harmonic components in current waveform of a single-phase AC input, without having to use a reactor of large capacity and the cooling system (refrigeration cycle) has a target delivery temperature. <P>SOLUTION: Voltage/current of a single-phase AC power supply 101 rectified by a first rectifier circuit 102 is inputted directly to an inverter 106, and the applying voltage to a motor 109 is calculated, by using a voltage smoothed by a second rectifier circuit 103 and a first capacitor 104. Consequently, the applied voltage to the motor 109 is substantially synchronized with the voltage waveform of the single-phase AC power supply, to obtain a low-cost and compact motor drive with the current waveform of the single-phase AC input 101 improved, without having to use a reactor of large capacity. Furthermore, the delivery temperature D2 is brought to a target delivery temperature. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a motor driving device employed in a cooling system such as an air conditioner or a refrigerator.

  Conventionally, this type of motor drive device rectifies AC of a single-phase AC power source into DC including a ripple component by a rectifier circuit in which diodes are bridge-connected, and includes the ripple component using a smoothing capacitor having a large capacity. It is known to smooth the voltage and drive the motor stably. Hereinafter, this technique is referred to as a first conventional technique.

  In addition, in order to reduce the size and cost of the motor drive device, the AC power source rectified voltage can be operated stably even if it is input to the inverter, improving the input current waveform from the single-phase AC power source to the rectifier circuit. A method has been proposed (see, for example, Patent Document 1). Hereinafter, this technique is referred to as a second conventional technique.

  FIG. 12 is a block diagram of a conventional motor driving device that does not use a smoothing capacitor, and corresponds to the second prior art.

  In FIG. 12, the AC power source 1 is converted into DC power having pulsation by the rectifier diode 2 and input to the inverter 3. The inverter 3 converts the rectified DC power into AC power and applies a desired voltage to the brushless motor 4.

  The inverter control unit 5 includes a dq conversion unit 6, a d-axis PI controller 7, a q-axis PI controller 8, and a PWM generation unit 9, and includes an input voltage to the inverter 3, a motor current flowing through the brushless motor 4, and When a motor current command value indicating a current value to be supplied to the brushless motor 4 is input and the input voltage value to the inverter 3 is smaller than the voltage value to be applied, the voltage phase of the applied voltage to the brushless motor 4 is maintained. Then, the inverter 3 is controlled.

By such control, even when the DC side voltage of the inverter 3 is low, the voltage is continuously applied without stopping the voltage application to the brushless motor 4, and even when a greatly pulsating voltage is input to the inverter 3. By realizing stable driving, the motor driving device is reduced in size.
Japanese Patent Laid-Open No. 2005-20986

  However, since the first prior art uses a smoothing capacitor having a large capacity, the input to the rectifier circuit flows only near the peak of the voltage. For this reason, harmonic regulations cannot be satisfied, and a large capacity reactor is used.

  Such a reactor has a problem that it is large in size and weight, leading to an increase in cost.

  In the second prior art, since there is no capacitor having a large smoothing capacity, current does not flow only near the peak of the single-phase AC voltage, but control is performed so as to keep the input voltage to the motor 4 constant. Therefore, in the section where the voltage of the single-phase AC input is lower than the voltage to be applied to the motor, the current waveform is greatly distorted as a result of trying to keep the current flowing due to the capacity of the LC in the circuit. As a result, the current increases and the efficiency of the motor 4 becomes poor.

  The present invention solves the above-described conventional problems, reduces harmonic components of the current waveform of a single-phase AC input without using a large-capacity reactor, satisfies the harmonic regulation, and is a cooling system (refrigeration system). It is an object of the present invention to provide a motor drive device in which the cooling system can be operated with the highest possible efficiency by moving the motor phase angle so that the discharge temperature of the cycle becomes the target discharge temperature.

  In order to solve the above-described conventional problems, the motor driving device of the present invention rectifies a single-phase AC power supply by a first rectifier circuit, and directly inputs the voltage / current to the inverter, and also applies the voltage applied to the motor. In this calculation, a voltage smoothed by the second rectifier circuit and the first capacitor is used.

  As a result, the voltage applied to the motor becomes a waveform substantially synchronized with the voltage waveform of the single-phase AC power supply, the current waveform of the single-phase AC power supply is improved, and the high-pressure side temperature of the cooling system, that is, the discharge-side temperature of the compressor By moving the motor phase angle so as to reach the target discharge temperature, the cooling system can always be operated with the highest efficiency as much as possible.

  The motor drive device of the present invention has a simple structure that improves the current waveform of a single-phase AC input without using a large-capacity reactor, etc., and can always be operated with high efficiency as much as possible. It is possible to provide a motor drive device that operates a highly efficient cooling system.

  The invention according to claim 1 is a single-phase AC power source, a first rectifier circuit that rectifies AC of the single-phase AC power source into DC, and an inverter that converts DC obtained from the first rectifier circuit into AC A motor having an AC input from the inverter as an input, a first capacitor connected between the DC buses of the inverter via a second rectifier circuit, and a first capacitor connected in parallel A load; voltage detecting means for detecting a voltage across the first capacitor; current detecting means for detecting a current of each phase of the motor; and a temperature on a discharge side of a compressor driven by the motor. The inverter is driven using the discharge temperature detecting means having the discharge temperature sensor, the voltage value detected by the voltage detecting means and the motor position signal detected by the current detecting means, A control means for controlling a voltage applied to the motor; and a motor phase calculation means for calculating a phase angle β of the voltage from the current flowing through the motor. The control means inputs a signal from the motor phase calculation means. The phase angle β is changed so that the discharge temperature from the discharge temperature detecting means becomes a predetermined target discharge temperature.

  By adopting such a configuration, the current waveform of a single-phase AC input can be improved with a simple configuration without using a reactor with a large capacity, and the system load is always increased as much as possible by operating through the discharge temperature. The cooling system can be operated efficiently, and as a result, it can be realized at a small size and at a low cost.

  In addition, a compressor motor having a large moment of inertia is less susceptible to torque fluctuations due to voltage fluctuations and can be driven more stably.

  According to a second aspect of the present invention, a load connected to the first capacitor is a power supply circuit for operating the control means.

  By adopting such a configuration, it is possible to share a load and a power source for driving the control means, and it is possible to provide a motor drive device that is smaller and less expensive.

  The invention according to claim 3 is the one in which a small-capacitance capacitor is connected between the DC buses of the first rectifier circuit, so that regenerative energy from the motor can be stored and used when the voltage drops. And a large torque can be generated by starting the motor.

  The invention described in claim 4 is such that the compressor is a reciprocating compressor, and this configuration has a larger moment of inertia than that of a scroll compressor, a rotary compressor, etc., and further stable driving. It can be done.

  The invention described in claim 5 comprises the cooling system including the compressor and including a condenser, a decompressor, an evaporator, and the like.

  As a result, it is possible to adopt it in refrigeration and air conditioning equipment such as refrigerators with strict harmonic regulations, and to provide a motor drive device that satisfies harmonic regulations at a small size and at low cost, and that always operates as efficiently as possible. Can do.

  In addition, since it is a small motor drive device, the volume ratio in the cabinet can be improved if it is used in a refrigerator, and the control circuit can be made compact if it is used in a room air conditioner. is there.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, 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, a single-phase AC power supply 101 is a commercial power supply, and is known to have an AC of 100 V, 50 Hz, or 60 Hz in Japan, and is connected to the first rectifier circuit 102.

  The first rectifier circuit 102 is configured by a circuit in which four diodes are bridge-connected.

  The second rectifier circuit 103 is connected so that current flows only from the plus side of the first rectifier circuit 102 to the plus side of the first capacitor 104, and for example, a diode can be employed. The means for consuming (absorbing) regenerative energy connected in parallel with the first capacitor 104 may be a resistor or the like, but in the first embodiment, the power supply circuit 105 is connected in parallel with the first capacitor 104. ing. As a result, power converted from a high voltage to a low voltage can be supplied to a circuit that requires stable power, such as the control means 107 that controls the inverter 106. As the power supply circuit 105, a switching regulator, a DC / DC converter, or the like can be used.

  The second capacitor 108 receives the voltage that has been full-wave rectified by the first rectifier circuit 102. The second capacitor 108 uses a second capacitor having a capacitance of 0.2 μF / W or less.

  Conventionally, the capacitance of the capacitor corresponding to the second capacitor 108 is determined by the ripple content of the DC voltage or the ripple current from the output capacitance (W or VA) of the inverter 106 or the input capacitance (W or VA) of the entire driving device. In general, the capacitance of the capacitor is determined in consideration of the characteristics of the ripple resistance of the smoothing capacitor.

  In consideration of these conditions, generally a capacity of about 2 to 4 μF / W has been secured. As a result, in the case of an output capacity of 200 W, an electrolytic capacitor of about 400 to 800 μF is used.

  On the other hand, in the first embodiment, a capacitor having a capacitance of 0.2 μF / W or less is used as the second capacitor 108. That is, in the case of an output capacity of 200 W, a capacitor of 40 μF or less is used.

  As the type of the second capacitor 108, a multilayer ceramic capacitor, a film capacitor, or the like can be used. In particular, a multilayer ceramic capacitor has recently been able to realize a high withstand voltage and large capacity capacitor on a chip. There is an advantage that it can be miniaturized. In the first embodiment, a multilayer ceramic capacitor having a capacitance of 1 μF is used for the second capacitor 108.

  The inverter 106 is a six-circuit, three-phase bridge connected to a set of diodes connected in the opposite direction to the switching elements. An IGBT, a bipolar transistor, an FET, or the like can be used as the switching element.

  A brushless DC motor (hereinafter referred to as a motor) 109 is driven by the three-phase output of the inverter 106. The stator of the motor 109 is provided with a three-phase star-connected winding, and this winding method may be concentrated winding or distributed winding. The rotor has a rare earth permanent magnet, and the arrangement method may be a surface magnet type (SPM) or a magnet embedded type (IPM). The permanent magnet may be a ferrite magnet or a rare earth magnet. If a rare earth magnet is used as the permanent magnet and the magnet weight is the same as that of the ferrite magnet, the motor efficiency can be improved, and the motor has the same performance as the motor using the ferrite magnet. In this case, the magnet weight can be reduced, and the motor weight can be reduced in weight and cost.

  The first voltage detection means 110 acquires the voltage across the first capacitor 104 and outputs the value to the control means 107.

  The position detection means 111 detects the current (u, v, w) flowing through each phase of the motor 109 and outputs the position signal (rotation angle signal) of the motor 109 to the control means 107 based on this current value. . The configuration of the position detection unit 111 is not specified as long as it is a unit that can detect the position of the motor 109. However, in the first embodiment, the second voltage detection unit 112, the current detection unit 113, and the motor phase calculation are performed. The means 114 is provided. The second voltage detection means 112 detects the voltage between the DC buses in the first rectifier circuit 102 and outputs it to the motor phase calculation means 114.

  The current detection means 113 detects the motor 109 current I and outputs it to the motor phase calculation means 114. The current detecting means 113 can be a current sensor, a shunt resistor, or the like. In that case, the shunt resistor has an advantage that it can be realized particularly at a small size and at low cost.

  The motor phase calculation means 114 performs calculation using the voltage detected by the second voltage detection means 112 and the current value of the motor 109 detected by the current detection means 113 as input, and thereby the phase angle β of the motor 109 is calculated. Is output to the control means 107.

  The control means 107 receives the phase angle β of the motor 109 that is the output of the position detection means 111 and determines a voltage to be applied to the motor 109. Then, the PWM duty width is determined from the voltage to be applied and the voltage detected by the first voltage detecting means 110, and the inverter 106 is driven.

  In the first embodiment, by setting the voltage detected by the first voltage detection unit 110 as an average voltage, a voltage necessary for driving the motor 109 can be applied, and thus the operation can be performed more stably.

  Here, the average voltage Vave of the single-phase AC power supply 101 can be expressed by the following equation from the maximum voltage Vmax.

Vave = 2 / π · Vmax (Formula 1)
Since the voltage detected by the first voltage detecting means 110 is smoothed, it is almost the maximum voltage. Therefore, the calculation result with the voltage detected by the first voltage detection means 110 as the maximum voltage can be used as the average voltage.

  Actually, when a voltage is detected using an AD converter, the first rectification, such as a method of multiplying the conversion coefficient when the AD conversion result is changed to a voltage by the coefficient represented by the above (formula 1) in advance Compared with a method in which the voltage between the DC buses in the circuit 102 is sampled finely and calculated, it can be easily obtained.

  In the first embodiment, since the single-phase AC power supply 101 is 100V, the maximum voltage of the first capacitor 104 is about 141V. Therefore, according to the above (Equation 1), about 0.64 times the maximum voltage is the average voltage, so the average voltage value is about 90V.

  Further, the change in the maximum voltage of the single-phase AC power supply 101 changes depending on the time constant of the capacitance in the power supply circuit 105 and the first capacitor 104, and The response speed can be adjusted by setting the capacity.

  The motor 109 drives a compression element 115a of a compressor 117, which will be described later. The compression element 115a is connected to the rotor shaft of the motor 109, and sucks, compresses and discharges refrigerant gas. The motor 109 and the compression element 115a are accommodated in the same hermetic container 116 to constitute the compressor 117.

  In the first embodiment, the cooling system configuration (refrigeration cycle) is such that the discharge gas compressed by the compressor 117 returns to the suction of the compressor 117 through the condenser 118, the decompressor 119, and the evaporator 120. For example, the condenser 118 radiates heat and the evaporator 120 absorbs heat, so that cooling and heating can be performed.

  Note that a heat exchanger may be further promoted by using a blower or the like for the condenser 118 or the evaporator 120 as necessary. Moreover, in this Embodiment 1, the evaporator 120 of the above-mentioned cooling system is provided in the refrigerator 121, and the refrigerator 121 is cooled.

  Further, in the cooling system configuration, a discharge temperature sensor 122 is provided on the discharge side of the compressor 117, and the detection signal of the discharge temperature sensor 122 is sent to the discharge temperature detection means 12 A constituting the position detection means 111. Entered. The discharge temperature detection unit 12A outputs the above-described temperature signal to the motor phase calculation unit 114.

  In addition, the energy from the motor 109 is returned by performing a slight deviation between the position of the motor 109 and the actual position of the motor 109 by the position detection unit 111 of the motor 109 or a weakening magnetic flux control for high torque operation. Even if a capacitor having a capacitance of 0.2 μF / W is selected, it is possible to absorb a steep voltage change and drive the motor 109 using the absorbed energy.

  Next, the operation contents of adjusting the phase angle β by the motor phase calculation means 114 by the current I from the position detection means 111, the voltage V from the second voltage detection means 112, and the discharge temperature detection means 12A are shown in FIG. 2 and FIG.

  FIG. 2 is an operation flow chart for adjusting the phase angle of the motor in the first embodiment, and FIG. 3 is a relationship diagram showing the relationship between the target discharge temperature and the motor control rotational speed.

  2, at Step 0, the target discharge temperature TD2 is extracted from the current rotation speed of the compressor 117 based on the relationship between the discharge temperature and the rotation speed shown in FIG. For example, if the current rotation speed is 24 rps, the target discharge temperature TD2 is 0 ° C.

  In Step 1, the discharge temperature D2 output from the discharge temperature detecting means 12A and the target discharge temperature TD2 extracted in Step 0 are compared to determine the phase angle β.

  In Step 1, the target discharge temperature TD2 is compared with the discharge temperature D2 detected this time. If the target discharge temperature TD2 is smaller, the process proceeds to Step 2.

  In Step 2, the phase angle is subtracted by 1 degree from the previous phase angle β, and the process proceeds to Step 3.

  In Step 1, the discharge temperature D2 is compared with the target discharge temperature TD2, and if the detected discharge temperature D2 is higher, the process proceeds to Step 4.

  In Step 4, the phase angle is added by 1 degree from the previous phase angle β, and the process proceeds to Step 3.

  In Step 3, if the discharge temperature D2 is not the same as the target discharge temperature TD2, the result is No, and the process proceeds to Step 1. If they are the same, the answer is Yes, and the operation flow ends.

  According to the operation flow of FIG. 2, the rotation speed (capacity) of the compressor 117 (motor 109) is controlled so that the discharge temperature D2 becomes the target discharge temperature TD2. For this purpose, the phase angle β of the motor 109 is controlled. To do. As a result, the operation of the cooling system can be made highly efficient.

  Next, the configuration of the compressor 117 will be described with reference to FIG. FIG. 4 is a cross-sectional view of the compressor in the first embodiment.

  In FIG. 4, oil 122 is stored in an airtight container 116 constituting a compressor 117 and a refrigerant 123 of R600a is sealed, and a motor 109 mainly composed of a stator 124 and a rotor 125, and driven by this. The compression element 115a is elastically supported by a spring or the like, so that vibration due to rotation of the motor 109 is difficult to propagate outside the compressor.

  The compression element 115a includes a main shaft portion 126 to which the rotor 125 is fixed and a crankshaft 128 composed of an eccentric shaft portion 127, and a cylinder 130 that supports the main shaft portion 126 of the crankshaft 128 and has a compression chamber 129. And a piston 131 that reciprocates in the compression chamber 129 and a connecting means 132 that connects the eccentric shaft portion 127 and the piston 131 to form a reciprocating compression mechanism.

  Therefore, in the first embodiment, even when the input voltage of the inverter includes a large pulsation, the vibration due to the pulsation and the noise accompanying the vibration are generated outside the compressor due to the characteristics and structure of the reciprocating compressor having a large inertia. It is difficult to leak.

  In Embodiment 1, R600a, which has a lower refrigeration capacity than R134a refrigerant, is used. Therefore, in order to ensure equivalent cooling performance, the volume of the compression chamber 129 needs to be larger than the compressor for R134a. And the piston 131 is enlarged.

  Accordingly, the motor inertia is also large, and even when the second capacitor 108 is set to a very small capacity and an inverter input voltage including a large pulsation is applied in the control device, it is less susceptible to vibration and noise. Become.

  The operation and action of the motor driving apparatus configured as described above will be described below, but in the first embodiment, it will be described as an inverter based on PWM (Plus Width Modulation) control.

  The first voltage detection unit 110, the position detection unit 111, the control unit 107, and the like are configured by an integrated circuit (LSI) centered on a microcomputer, as is well known, from the relationship of processing various signals.

  First, when control is performed using the voltage between the DC buses in the first rectifier circuit 102 without using the average voltage as in the prior art, using FIGS. 1, 5, 6, 7, and 8. Will be described.

  FIG. 5 is a waveform diagram showing a part (half wave) of the transition of the voltage between the DC buses with the power supply frequency of 50 Hz in the motor drive device of the first embodiment. FIG. 6 is a graph showing a part (half wave) of the transition of the PWM duty for each carrier cycle when the DC bus voltage value by the conventional control is used. FIG. 7 is a graph showing a part (half wave) of the average voltage transition for each carrier cycle applied to the motor when the DC bus voltage value according to the conventional control is used. FIG. 8 is a waveform diagram showing a part (half wave) of a transition of current flowing in the motor when a DC bus voltage value by conventional control is used.

  In these waveform diagrams and graphs, one cycle of the waveform is set to 20 milliseconds for convenience, and here, the half-wave component of the power supply waveform will be mainly described for convenience.

  The control unit 107 determines the voltage to be applied to the motor 109 using the position information of the motor 109 detected by the position detection unit 111. Here, the voltage applied to the motor 109 is 64 V for convenience of explanation.

  At this time, in the conventional method, the PWM duty is calculated using the DC bus voltage, so in FIG. 4, the PWM duty width is shown in FIG. 6 in the interval from T1 milliseconds to T2 milliseconds where the DC bus voltage is 64 V or more. As shown in FIG. 7, the central portion is controlled to be small, and as a result, the average voltage for each carrier period in the section from T1 milliseconds to T2 milliseconds is controlled to be 64 V as shown in FIG.

  On the other hand, in order to apply the voltage to the motor 109 to the maximum in the section from 0 milliseconds to T1 milliseconds and from T2 milliseconds to 10 milliseconds, where the DC bus voltage is 64 V or less, As shown in FIG. 6, the duty is 100%. Therefore, the voltage applied in the section becomes equal to the voltage of the DC bus as shown in FIG.

  As a result, as shown in FIG. 8, the current flowing through the motor 109 is substantially constant during the period from T1 milliseconds to T2 milliseconds, and the voltage decreases from T2 milliseconds to 10 milliseconds. As a result, the current value decreases. Further, in the portion where the input voltage shown in the section from T2 milliseconds to 10 milliseconds becomes 0 V, in FIG. 8, since the current is kept flowing by the inductor component of the single-phase AC power source 101, the current does not become zero. In addition, at the rising edge of the voltage from 0 V, a current that continues to flow at the falling portion of the previous waveform flows, so that the current waveform has a sawtooth portion P in the current waveform from 0 ms to T1 ms. And has a waveform including harmonic components.

  As described above, when the control is performed using the voltage between the DC buses in the first rectifier circuit 102 without using the average voltage as in the conventional case, the current waveform includes a harmonic component. .

  Next, in order for the control means 107 to calculate the voltage applied to the motor 109, the case where the average voltage of the DC bus voltage with the power frequency detected by the first voltage detection means 110 as 50 Hz is used is shown in FIG. , FIG. 5, FIG. 9, FIG. 10, and FIG.

  FIG. 9 is a graph showing the transition of the PWM duty for each carrier period when the average voltage value in the first embodiment is used. FIG. 10 is a graph showing the transition of the average voltage for each carrier cycle applied to the motor when the average voltage value in the first embodiment is used. FIG. 11 is a waveform diagram showing the transition of the current flowing through the motor when the average voltage value in the first embodiment is used.

  First, the average voltage detected by the first voltage detection means 110 is about 90V as described above, and the duty required to output 64V to the motor 109 is calculated to be about 71%. As described above, when the DC bus voltage of the first rectifier circuit 102 is used for duty calculation, the duty fluctuates as shown in FIG. 6, but since the average voltage is used for calculation, the duty is shown in FIG. As shown in FIG. 4, the value is constant over the entire period from 0 milliseconds to 10 milliseconds.

  As a result, the average voltage transition for each carrier cycle applied to the motor 109 is substantially the same as the voltage transition value of the single-phase AC power supply 101 shown in FIG. 5 multiplied by about 0.71 as shown in FIG. To do.

  Thus, in the case of the duty control using the above-described average voltage, the voltage applied to the motor 109 changes in a sine wave shape, and therefore, the change in the total current flowing in the motor 109 also has a sine wave shape as shown in FIG. Thus, the harmonic component is greatly improved.

  As described above, in the first embodiment, the single-phase AC power source 101, the first rectifier circuit 102 that rectifies the AC of the single-phase AC power source 101 into DC, and the DC obtained from the first rectifier circuit 102. An inverter 106 that converts AC into AC, a motor 109 that receives AC from the inverter 106, a first capacitor 104 that is connected between the DC buses of the inverter 106 via a second rectifier circuit 103, A power supply circuit 105 serving as a load connected in parallel with one capacitor 104, a first voltage detection unit 110 that detects a voltage across the first capacitor 104, and a position detection unit 111 that detects the position of the motor 109. The inverter 10 using the voltage value detected by the first voltage detection means 110 and the position signal of the motor 109 detected by the position detection means 111. , And a power calculation means 115 for calculating power from the voltage of the second voltage means 112 and the current of the position detection means 111, thereby controlling the voltage applied to the motor 109. Is substantially synchronized with the voltage waveform of the single-phase AC power supply 101, and the current waveform of the single-phase AC power supply 101 can be improved without using a large reactor or capacitor. A low-cost motor drive device can be provided.

  Furthermore, since the phase angle β of the motor 109 is controlled based on the temperature on the discharge side of the compressor 117, a highly efficient operation can always be performed with the lowest power as much as possible.

  In addition, since the load connected in parallel with the first capacitor 104 is a low voltage power source for operating the control unit 107, the power source and the load for driving the control unit 107 can be shared, and the size can be further reduced. A low-cost motor drive device can be provided.

  Furthermore, by connecting a second capacitor 108 having a small capacity between the DC buses of the first rectifier circuit 102, regenerative energy from the motor 109 can be stored and used when the voltage drops, generating a larger torque. It becomes possible to make it.

  Further, by using the motor 109 for driving the compressor 117, the motor 109 of the compressor 117 having a large moment of inertia is less susceptible to torque fluctuation due to voltage fluctuation, and can be driven more stably.

  Further, when the compressor 117 is a reciprocating type compressor, the moment of inertia is larger than that of a scroll type compressor, a rotary type compressor, or the like, and a more stable drive is possible.

  Further, by setting the refrigerant compressed by the compressor 117 to R600a, the refrigerating capacity is lower than that of R134a that has been generally used in refrigerators and the like, and the cylinder of the compressor 117 is used in order to produce the same refrigerating capacity Even if the volume is increased, the moment of inertia further increases due to this, so that the drive stability is improved as the moment of inertia increases as described above.

  Therefore, the compressor 117 having the motor driving device is provided in a cooling system configured with the condenser 118, the decompressor 119, the evaporator 120, etc., and the harmonic regulation is achieved by adopting this cooling system in the refrigerator. A satisfactory refrigerator is obtained. In addition, since the motor driving device is small, it is possible to increase the internal volume ratio of the refrigerator, and it is possible to provide an easy-to-use refrigerator that has the same outer dimensions and a larger storage capacity.

  In addition, by applying the cooling system to the air conditioner, it is possible to reduce the size of the air conditioner, and it is possible to configure an air conditioner that reduces the harmful effects of harmonics at low cost. As a result, the degree of freedom of installation space in the air conditioner can be increased.

  As described above, the motor drive device according to the present invention can be suppressed in harmonics at a small size and at low cost, and can always be operated with high efficiency as much as possible. Therefore, it can be widely applied to devices equipped with a cooling system. Is.

1 is a block diagram of a motor drive device according to Embodiment 1 of the present invention. Operation flow chart for adjusting the phase angle of the motor in the first embodiment FIG. 6 is a relationship diagram showing the relationship between the target discharge temperature and the motor control rotation speed in the cooling system of the first embodiment. Sectional drawing of the compressor in Embodiment 1 Half-wave waveform diagram showing a part of the transition in the DC bus voltage of the motor drive device in the first embodiment The graph which shows a part (half wave) transition of the PWM duty factor for every carrier period when the DC bus voltage value by the conventional control is used The graph which shows a part (half wave) of the average voltage transition for every carrier period applied to the motor when the DC bus voltage value by the conventional control is used Waveform diagram showing a part (half wave) of the current transition through the motor when using the DC bus voltage value under conventional control The graph which shows a part (half wave) transition of the PWM duty factor for every carrier period when using the average voltage value in Embodiment 1 of this invention The graph which shows a part (half wave) of average voltage transition for every carrier period applied to the motor at the time of using the average voltage value in Embodiment 1 Waveform diagram showing a part (half wave) of a current transition flowing in the motor when using the average voltage value in the first embodiment Block diagram of a motor drive device in the prior art

Explanation of symbols

12A Discharge temperature detection means 101 Single-phase AC power supply 102 First rectifier circuit 103 Second rectifier circuit 104 First capacitor 105 Power supply circuit 106 Inverter 107 Control circuit 108 Second capacitor 109 Motor 110 First voltage detector 111 Position detecting means 112 Second voltage detecting means 113 Current detecting means 114 Motor phase calculating means 116 Sealed container 117 Compressor 118 Condenser 119 Decompressor 120 Evaporator 121 Inside 122 Discharge temperature sensor 123 Refrigerant 124 Stator 125 Rotor D2 Discharge temperature TD2 Target discharge temperature

Claims (5)

  A single-phase AC power source, a first rectifier circuit that rectifies AC of the single-phase AC power source into DC, an inverter that converts DC obtained from the first rectifier circuit, and AC obtained from the inverter. An input motor, a first capacitor connected via a second rectifier circuit between the DC buses of the inverter, a load connected in parallel with the first capacitor, and the first capacitor Discharge temperature detection comprising voltage detection means for detecting voltage at both ends, current detection means for detecting the current of each phase of the motor, and a discharge temperature sensor for detecting the temperature on the discharge side of the compressor driven by the motor And a voltage applied to the motor by driving the inverter using the voltage value detected by the voltage detecting means and the motor position signal detected by the current detecting means. Control means for controlling, and motor phase calculation means for calculating the phase angle β of the voltage from the current flowing through the motor. The control means inputs a signal from the motor phase calculation means, and the discharge temperature detection means The motor drive device that changes the phase angle β so that the discharge temperature from the air reaches a predetermined target discharge temperature.   The motor driving apparatus according to claim 1, wherein a load connected to the first capacitor is a power supply circuit for operating the control means.   The motor driving device according to claim 1, wherein a small-capacitance capacitor is connected between the DC buses of the first rectifier circuit.   The motor driving device according to any one of claims 1 to 3, wherein the compressor is a reciprocating compressor.   The motor driving device according to any one of claims 1 to 4, wherein a cooling system including the compressor and including a condenser, a decompressor, an evaporator, and the like is configured.

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