JP3278188B2 - Inverter device for motor drive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device suitable for driving an electric motor.

[0002]

2. Description of the Related Art Conventionally, a current type inverter device and a voltage type inverter device have been provided as inverter devices for driving a motor. FIG. 8 is an electric circuit diagram showing a configuration of a three-phase current source inverter device. A thyristor bridge rectifier circuit 51 having a three-phase AC power supply as an input, a reactor 52 for functioning as a constant current source, and a reactor 52
And a current-type three-phase full-bridge inverter 53 that obtains a three-phase alternating current by switching the current obtained by the above and supplies the three-phase alternating current to the electric motor 54 as a load. A series connection of three pairs of thyristors 53a (of each phase) constituting a current type three-phase full-bridge inverter 53 is connected to a forward-connected diode 53b, and a commutation capacitor 53c is connected between each phase. ing.

FIG. 9 is an electric circuit diagram showing a configuration of a three-phase voltage source inverter device. Three pairs of (each phase) switching constituting a voltage type three-phase full-bridge inverter 62 between terminals of a DC power supply 61. A series circuit of the elements 62a is connected, and a diode 62b is connected in parallel with each switching element 62a. Reference numeral 63 denotes a three-phase motor as a load. The DC power supply 61 simply shows a converter that receives a three-phase AC power supply as an input.

The three-phase current source inverter device switches the thyristors 53a of each phase so that the current waveform supplied to the load becomes a square wave.
Since the voltage waveform becomes a sine wave shape by switching the 3a in this manner, the number of times of switching of the thyristor 53a per cycle can be reduced, and a good waveform can be obtained. Focusing on the advantage that the number of switching operations per cycle can be reduced, the present invention is applied to driving of a large motor.

The three-phase voltage-source inverter device switches the switching elements 62a of each phase so that the voltage waveform supplied to the load becomes a square wave. Can be simplified.

[0006]

In the above three-phase current source inverter device, the commutation capacitor 53c must be connected between each phase, so that not only the circuit configuration becomes significantly complicated, but also the power supply is connected to a constant current source. In order to function as, the inductance of the reactor 52 must be increased, and since the current waveform is made into a square waveform, depending on load conditions, inconveniences such as overvoltage and instability may occur.

In the three-phase voltage source inverter, since the voltage waveform is controlled in a square wave form, the voltage waveform contains many harmonic components, and the noise becomes large and the efficiency becomes poor. Moreover, there is a possibility that an overcurrent occurs, and if the overcurrent occurs, a disadvantage that the switching element is destroyed occurs. In order to solve such inconveniences, generally, the switching element 62a of each phase is PWM-controlled so that the voltage waveform approximates a sine wave. However, the number of switching operations per cycle is inevitably increased. I have to. Therefore, the number of switching times that the three-phase full-bridge inverter 62 can follow is restricted.

Further, the present inventors have solved the above-mentioned conventional three-phase current source inverter device and three-phase voltage source inverter device, and have developed a new motor drive inverter as a motor drive inverter device having both advantages. The device was proposed. FIG. 10 is an electric circuit diagram showing the configuration of the motor driving inverter device proposed above, and shows a three-phase AC power supply 7.
Three-phase diode bridge rectifier circuit 72 with 1 as input
And a step-down chopper circuit 73 using a DC voltage obtained by the three-phase diode bridge rectifier circuit 72 as a power supply, and performing a predetermined switching operation by using an output of the step-down chopper circuit 73 as an input to supply three-phase power to a motor 76 as a load. It has a voltage source three-phase full-bridge inverter 74 to be supplied and a regenerative power bypass diode 75 reversely connected in parallel to the step-down chopper circuit 73.

The inverter device for driving a motor having the above configuration can omit a commutation capacitor which is indispensable in a conventional current source inverter device, and can eliminate a series diode connected in series with a switching element. As a result, the circuit configuration can be simplified. Further, it is possible to obtain a load current and a voltage waveform close to the voltage-source inverter device and a load current and a voltage waveform close to the current-source inverter according to the length of the conduction period of the regenerative power bypass diode.

However, there is a need to achieve higher efficiency, lower noise, less leakage current, and to achieve stable starting.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has a simple circuit configuration and is characterized by the characteristics of a current source inverter device and a voltage source inverter device depending on the size of a load, the magnitude of an input voltage, and the like. It is another object of the present invention to provide an electric motor driving inverter device that can achieve higher efficiency, lower noise, reduce leakage current, and achieve stable starting.

[0012]

According to a first aspect of the present invention, there is provided an inverter device for driving a motor, comprising: a bridge rectifier circuit having an AC power supply as an input; and a DC voltage obtained by the bridge rectifier circuit. A step-down chopper circuit for stepping down, a voltage-type bridge inverter inputting the DC power obtained by the step-down chopper circuit, a regenerative power bypass diode reversely connected in parallel with the step-down chopper circuit, and an induced voltage of the motor as inputs. And an inverter control means for supplying a switching command to the voltage-type bridge inverter so as to make the power factor of the electric motor substantially equal to one.

In the inverter device for driving a motor according to the second aspect, a capacitor is further connected between output terminals of the step-down chopper circuit. The motor driving inverter device according to claim 3 employs a brushless DC motor as the motor. The motor driving inverter device according to claim 4 supplies a switching command to operate the voltage-type bridge inverter in a predetermined pattern at the time of starting, and responds to the generation of the induced voltage larger than the predetermined value by the brushless DC motor. A starting means for operating the inverter control means is further included.

According to a fifth aspect of the present invention, as the inverter control means, a resistor voltage dividing circuit for detecting a phase voltage of the motor, an integrator receiving the phase voltage, and discriminating the sign of the output of the integrator as the inverter control means. A circuit including a comparator, a photocoupler, and a logic operation circuit that obtains and outputs a switching command based on the positive / negative determination result supplied through the photocoupler is used.

[0015]

According to the motor driving inverter device of the present invention, a DC voltage rectified by the bridge rectifier circuit can be obtained, and the current flowing through the reactor can be controlled to DC by the step-down chopper circuit. By operating the voltage-type bridge inverter, a desired AC current can be supplied to the motor as a load.

Here, the step-down chopper circuit functions as a constant current source when viewed from the voltage-type bridge inverter. However, when the regenerative power bypass diode is conducting, the output current of the step-down chopper circuit is reduced. Is not constant, the input voltage and the output voltage of the step-down chopper circuit become substantially equal, and conversely, the output current of the step-down chopper circuit becomes constant when the regenerative power bypass diode is not conducting. Therefore, if the conduction period of the regenerative power bypass diode is short, the output current of the step-down chopper circuit becomes substantially direct current, and the load current and voltage have the waveforms of the current source inverter device. Conversely, if the conduction period of the regenerative power bypass diode is long, the period during which the output voltage of the step-down chopper circuit becomes constant increases and becomes substantially DC, and the load current and voltage become waveforms of the voltage type inverter device. That is, it has the characteristics of the current source inverter device and the voltage source inverter device.

Then, using the induced voltage of the motor as an input,
Since the inverter control means supplies a switching command to the voltage type bridge inverter so that the power factor of the motor becomes almost 1, the conduction period of the regenerative power bypass diode can be shortened, and the harmonic component can be further reduced. To make the load voltage waveform closer to a sine wave,
Motor driving with higher efficiency and lower noise than the motor driving inverter device shown in FIG. 10 can be achieved.

As is apparent from the above description, a series diode connected in series to a thyristor as a switching element in a conventional current-source inverter device can be replaced with a single regenerative power bypass diode. Since the provided commutation capacitor can be omitted, the circuit configuration as a whole can be simplified.

In the inverter device for driving a motor according to claim 2, since a capacitor is further connected between the output terminals of the step-down chopper circuit, a function as a filter is achieved by the capacitor and the reactor of the step-down chopper circuit.
Harmonic components can be further reduced, and higher efficiency and lower noise can be achieved, and leakage current, which is particularly problematic when a compressor is driven by an electric motor, can be reduced. Further, since the switching frequency of the switching element of the step-down chopper circuit can be reduced, the loss can be reduced, and higher efficiency can be achieved.

According to the third aspect of the present invention, since the brushless DC motor is employed as the motor, the motor itself does not generate heat and the rotor can be miniaturized. As a result, high-speed rotation is possible, and it is possible to easily cope with a case where high-speed rotation is performed in which PWM control is impossible due to a high frequency.

According to a fourth aspect of the present invention, the motor-driven inverter device supplies a switching command to operate the voltage-type bridge inverter in a predetermined pattern at the time of starting, and the brushless DC motor generates an induced voltage larger than a predetermined value. Since it further includes starting means for operating the inverter control means in response, open-loop control is performed only when the brushless DC motor cannot be stably operated in the open loop state, and the brushless DC motor starts to some extent. After the induced voltage is generated,
The operation can be stably continued by the inverter control means. Also, the brushless D by the above open loop control
An overcurrent that is likely to occur at the time of starting the C motor can be prevented by current control of the switching element of the step-down chopper circuit, and stable starting can be achieved.

According to a fifth aspect of the present invention, as the inverter control means, a resistance voltage dividing circuit for detecting a phase voltage of the motor, an integrator receiving the phase voltage, and a positive / negative output of the integrator are used as the inverter control means. Since a motor including a comparator for discriminating, a photocoupler, and a logic operation circuit for obtaining and outputting a switching command based on the positive / negative discrimination result supplied through the photocoupler is used, a rotational position sensor (a brushless motor as a motor) It is not necessary to use a DC motor), and the main circuit functions as a current-type inverter during low-speed rotation, which is difficult to detect with conventional sensorless control. As the values become closer, it is necessary to set the constants of the integrators and comparators that constitute the inverter control means very strictly. Is eliminated, by performing a closed loop control using the inverter control unit, it is possible to extend the low-speed rotation region capable of closed loop control, a stable closed-loop control can be achieved over a wide range.

[0023]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is an electric circuit diagram showing an embodiment of an inverter device for driving a motor according to the present invention.
, A step-down chopper circuit 3 that uses a DC voltage obtained by the three-phase diode bridge rectifier circuit 2 as a power supply, and performs a predetermined switching operation using an output of the step-down chopper circuit 3 as an input. Three-phase full-bridge inverter 4 for supplying three-phase power to a brushless DC motor 6 as a load, a regenerative power bypass diode 5 reversely connected in parallel to the step-down chopper circuit 3, and a brushless DC motor 6 An inverter control circuit 8 that supplies a switching command to control the brushless DC motor 6 so that the power factor becomes substantially 1 by using the induced voltage of the input as an input, and a small-capacity provided between the output terminals of the step-down chopper circuit 3. It has a capacitor 9 and a starting circuit 10.

In the inverter device for driving a motor having the above-described configuration, the output current of the step-down chopper circuit 3 becomes substantially DC when the regenerative power bypass diode 5 is not conductive, but the regenerative power bypass diode 5 is conductive. In this state, the output current of the step-down chopper circuit 3 does not become constant, and the input voltage and the output voltage of the step-down chopper circuit 3 become substantially equal. Therefore, if the period during which the regenerative power bypass diode 5 conducts is short, the output current of the step-down chopper circuit 3 becomes substantially direct current, and the load current and voltage have the waveform of the current source inverter device. Conversely, if the period during which the regenerative power bypass diode 5 conducts is long, the period during which the output voltage of the step-down chopper circuit 3 becomes constant increases, and becomes substantially DC, so that the load current and voltage are similar to the waveform of the voltage source inverter device. become.

When performing this operation,
The switching command is supplied to the voltage-type three-phase full-bridge inverter 4 by the inverter control circuit 8 using the induced voltage of the brushless DC motor 6 as an input, so that the power factor of the brushless DC motor 6 becomes almost 1, so that the regenerative power bypass diode Can reduce the conduction period of the current source and make it closer to the waveform of the current source inverter, so that the higher harmonic component is reduced and the voltage waveform becomes closer to a sine wave, so that the brushless DC motor has higher efficiency and lower noise. 6 operations can be achieved.

Further, since the small-capacity capacitor 9 is connected between the output terminals of the step-down chopper circuit 3, the load current ripple can be reduced. As a result, higher harmonic components are reduced, and higher efficiency and lower noise operation can be performed.
Furthermore, leakage current, which is particularly problematic when a compressor is used as a load, can be reduced. Furthermore, since the load current ripple can be reduced by the capacitor 9,
The switching frequency of the switching element 3a of the step-down chopper circuit 3 can be reduced, and the switching loss can be reduced.

At the start, the brushless DC motor 6
The control by the inverter control circuit 8 cannot be performed because the induced voltage of the DC motor 6 is 0, but the switching command is forcibly supplied to the voltage type three-phase full-bridge inverter 4 by the starting circuit 10 so that the brushless DC motor 6
Starting can be achieved. After a certain amount of induced voltage is generated, a switching command is supplied by the inverter control circuit 8 to perform the above operation. When the operation is performed by the starting circuit 10, an overcurrent may flow. However, the overcurrent can be reliably prevented by the step-down chopper circuit 3, and a stable starting can be performed.

In addition, when the brushless DC motor 6 is used, the rotation position sensor, which has been essential, becomes unnecessary, and the main circuit functions as a current source inverter at low speed rotation which is difficult to detect with the conventional sensorless control circuit. The voltage waveform is close to a sine wave. Therefore, a low-speed region in which closed-loop control is possible can be extended, and stable operation can be achieved over a wide range. In addition, the constants of the integrator 8b, the comparator 8c and the like included in the inverter control circuit 8 do not need to be set very strictly, and the setting of the constant can be simplified.

Next, each component will be described in detail. The three-phase diode bridge rectifier circuit 2 employs a diode 2a as a rectifier instead of a phase-controlled thyristor and uses a constant voltage source by an electrolytic capacitor 2b, so that the configuration can be simplified. The step-down chopper circuit 3 includes a reactor 3b, a switching element 3a that is switching-controlled to control the current of the reactor 3b to DC, and a diode 3c connected in parallel with the electrolytic capacitor 2b via the switching element 3a. Have been. Therefore, the current of the reactor 3b can be controlled by the switching element 3a and the diode 3c whose switching is controlled, and by setting the switching frequency of the switching element 3a high, the reactor 3
The capacity of b can be reduced. Further, when controlling the phase of the thyristor, conventionally, it was necessary to switch six thyristors, but one switching element 3a
It only needs to be switched. The chopper control circuit for switching the switching element 3a includes a subtractor 3d that calculates a difference between the current command value IL * and the reactor current IL, and a PI control unit 3e that receives the subtraction result of the subtractor 3d as an input. And a comparator 3f for comparing the magnitude of a reference signal (for example, a triangular wave signal) of a predetermined frequency with the output signal from the PI control unit 3e and supplying the comparison result signal as a switching command to the switching element 3a. Therefore, when there is a possibility that an overcurrent flows to the electric motor as represented at the start, the overcurrent can be suppressed. As a result, it is possible to prevent an excessive current from flowing at the time of starting, and to start the electric motor softly.

The above voltage type three-phase full bridge inverter 4
Is a diode 4 in parallel with the switching element 4a of each phase.
Since only b is connected, and no commutation diode between the phases is required, the configuration can be significantly simplified. The regenerative power bypass diode 5 includes a step-down chopper circuit 3.
Of the switching element 3a and the reactor 3b are reversely connected in parallel with the series circuit. Therefore, regenerative power bypass diode 5 is turned on only when the output terminal voltage of reactor 3b is higher than the voltage between terminals of electrolytic capacitor 2b of three-phase diode bridge rectifier circuit 2.

The inverter control circuit 8 includes a resistance voltage dividing circuit 8 for detecting a phase voltage of the brushless DC motor 6.
a, an integrator 8b receiving the phase voltage detected by the resistor voltage dividing circuit 8a as an input, a comparator 8c determining whether the output of the integrator 8b is positive or negative, and a photocoupler 8d receiving the determination result of the comparator 8c as an input. And a logic operation circuit 8e that receives a signal from the photocoupler 8d as an input and obtains and outputs a switching command. However, the integrator 8b, the comparator 8c, and the photocoupler 8d are provided for three phases (see FIG. 2). Therefore, each phase voltage is integrated by the integrator 8b, the comparator 8c determines whether the phase voltage is positive or negative, and is supplied to the logical operation circuit 8e through the photocoupler 8d. The logic operation circuit 8e obtains and outputs a switching command to the voltage-type three-phase full-bridge inverter 4 based on the positive / negative determination result of each phase so that the phase voltage and the line current become the same phase. As a result, the power factor of the brushless DC motor 6 becomes substantially 1, so that the conduction period of the regenerative power bypass diode 5 can be shortened, harmonic components can be reduced, and the load voltage waveform can be made closer to a sine wave. So, brushless DC motor 6
Operation efficiency and noise can be reduced. FIG. 3 is a signal waveform diagram of each part. When each phase voltage detected by the resistance voltage dividing circuit 8a is as shown in FIG.
The integrated waveform of each phase is as shown in FIG. 3B, and the result of the positive / negative discrimination by the comparator 8c is shown in FIGS.
(E) is as shown. Note that each phase voltage is Vu, V
v and Vw. These positive / negative determination results are supplied to the logical operation circuit 8e, and output a switching command to the voltage type three-phase full-bridge inverter 4 as shown in FIGS. Specifically, for example, the switching command for the u-phase upper switching element is set so that the ON command is issued when the v-phase integration signal is positive and the w-phase integration signal is negative.

The integrator 8b can remove noise included in the voltage waveform, and the gain of the integrator 8b is proportional to 1 / f, so that accurate calculation can be performed even at low speeds where the voltage is low. Thus, the power factor of the brushless DC motor 6 can be made approximately 1. The photocoupler 8d is for ensuring insulation, and can be replaced by an isolation amplifier or the like. However, it is preferable to use a photocoupler in consideration of cost and the like.

As shown in FIG. 4, the starting circuit 10
Start-up control circuit 10a for outputting a predetermined switching command, gate circuit 10b for selectively outputting a switching command from start-up control circuit 10a or a switching command from inverter control circuit 8, and operation of gate circuit 10b And a gate control circuit 10c for controlling the Reference numeral 10d denotes a single-throw switch for allowing or preventing the operation of the gate circuit 10b. The gate control circuit 10c includes a double-throw switch 10c1 which is switched to output any one of the switching commands. , And a pair of AND gates 10c2 and 10c3 controlled by a single throw switch 10d. Gate circuit 10
b is a pair of AND gates 10b controlled by output signals from AND gates 10c2 and 10c3, respectively.
1 and 10b2, an OR gate 10b3 to which the output signals of both AND gates 10b1 and 10b2 are input, and an inverter 10b4.

Therefore, the single-throw switch 10d is
By setting the state to the F state, the start-time control circuit 10a can be operated, and both AND gates 10c2 and 10c3 can be opened. In this state, the double throw switch 10
Any one of the AND gates 10c2 and 10c2 corresponding to the state of c1
A gate circuit control signal is output from 10c3, and the corresponding AND gates 10b1 and 10b2 are opened. As a result, if the AND gate 10b2 is open, the switching command from the start-up control circuit 10a is applied to the OR gate 10b.
3 and the inverter 10b4 to supply the voltage-type three-phase full-bridge inverter 4 to the AND gate 10b1.
Is open, the switching command from the inverter control circuit 8 is applied to the OR gate 10b3 and the inverter 10b.
The voltage is supplied to the voltage-type three-phase full-bridge inverter 4 through the inverter 4.

FIG. 5 shows that the brushless DC motor is driven by using the motor driving inverter device having the above-mentioned structure, and is operated under no load and 900 rpm. p. m. In this case, the load voltage and load current are shown, and the load current has a substantially square waveform and the load voltage has a substantially sinusoidal waveform, which indicates that the characteristics of the current source inverter device are exhibited. Also, it can be seen that the phase of the load voltage is the same as the phase of the load current. In this case, the power factor was 95%, the voltage waveform was a clean sine wave, and the noise and vibration were very small. FIG. 6 shows that the load is 1 kW and 900 r. p. m. The load voltage,
It shows the load current, and shows that the load voltage is substantially sinusoidal and the load current is substantially square-wave, indicating the characteristics of the current-source inverter device.

FIG. 7 shows the starting characteristics. Open loop control is performed by the starting circuit 10 for an initial predetermined time (see the range of T1 in FIG. 7), and thereafter, based on the phase voltage of the brushless DC motor 6. This figure shows a case where the double-throw switch 10c1 is switched to perform closed-loop sensorless control by the inverter control circuit 8. As is clear from FIG. 7, the current value is 5 A or less during the period in which the open loop control is being performed, and it can be seen that the overcurrent can be reliably prevented. Further, the brushless DC motor 6 is accelerated substantially linearly while the constant current control is performed by the step-down chopper circuit 3, and the rotation speed is set to 1500 rpm. p. m. , The voltage is saturated, the torque is lost, and the constant current control is released. In addition, 1500r. p. m. Instability during high-speed rotation in the vicinity is hardly recognized.

The present invention is not limited to the above-described embodiment. For example, the present invention can be applied to driving an electric motor other than a brushless DC motor, and various design changes can be made without departing from the scope of the present invention. Can be applied.

[0038]

As described above, according to the first aspect of the present invention, the step-down chopper is incorporated in the three-phase voltage source inverter, and the diode for regenerative power bypass is reversely connected in parallel with the step-down chopper, so that the circuit configuration is simplified. The characteristics of the current source inverter and the voltage source inverter can be obtained without changing the circuit configuration.
Since the motor is controlled so as to be as follows, the conduction time of the regenerative power bypass diode can be shortened, and the harmonic component is reduced, so that the voltage waveform becomes closer to a sine wave,
This has the specific effect that higher efficiency and lower noise can be achieved.

According to the second aspect of the present invention, since a capacitor is further connected between the output terminals of the step-down chopper circuit, a function as a filter is achieved by the capacitor and the reactor of the step-down chopper circuit, and the harmonic component is further reduced. In addition, higher efficiency and lower noise can be achieved, and leakage current, which is particularly problematic when a compressor is driven by an electric motor, can be reduced.In addition, the switching frequency of the switching element of the step-down chopper circuit can be reduced. There is a specific effect that loss can be reduced and higher efficiency can be achieved.

According to a third aspect of the present invention, in addition to the effects of the first and second aspects, the motor itself is capable of high-speed rotation, and has a high frequency so that PWM control is impossible due to a high frequency. There is a special effect that even if the operation is performed, it can be easily dealt with. The invention according to claim 4 performs the open loop control only at the time of starting the brushless DC motor which cannot continue the operation stably with the open loop, and after the brushless DC motor starts and the induced voltage is generated to some extent. The operation can be stably continued by the inverter control means, and the overcurrent which is likely to occur at the time of starting the brushless DC motor by the open loop control can be prevented by the current control of the switching element of the step-down chopper circuit. It has a unique effect of being able to achieve starting.

According to the fifth aspect of the present invention, there is no need to provide a rotational position sensor (which is indispensable when a brushless DC motor is used as the electric motor) in the electric motor, and it is difficult to detect by the conventional sensorless control. At low speed rotation, the main circuit functions as a current source inverter, and as the voltage waveform approaches a sine wave, it is not necessary to set the constants of the integrators and comparators constituting the inverter control means very strictly. By performing the closed loop control using the inverter control means, the low speed rotation region where the closed loop control can be performed can be expanded, so that there is a specific effect that stable closed loop control can be achieved over a wide range.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of a motor driving inverter device of the present invention.

FIG. 2 is an electric circuit diagram showing a configuration of an inverter control circuit in detail.

FIG. 3 is a diagram showing signal waveforms at various parts of the inverter control circuit.

FIG. 4 is an electric circuit diagram showing a configuration of a starting circuit in detail.

5 drives a brushless DC motor using the motor driving inverter device having the configuration shown in FIG.
r. p. m. FIG. 6 is a waveform diagram showing load voltage and load current when the state is set to “1”.

6 drives a brushless DC motor using the motor driving inverter device having the configuration shown in FIG. 1 to obtain a load of 1 kW and 900 r.p.m. p. m. FIG. 6 is a waveform diagram showing load voltage and load current when the state is set to “1”.

FIG. 7 is a diagram showing starting characteristics.

FIG. 8 is an electric circuit diagram showing a configuration of a conventional three-phase current source inverter device.

FIG. 9 is an electric circuit diagram showing a configuration of a conventional three-phase voltage source inverter device.

FIG. 10 is an electric circuit diagram showing a configuration of an inverter device for driving a motor proposed by the present inventors.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 three-phase AC power supply 2 three-phase diode bridge rectifier circuit 3 step-down chopper circuit 4 voltage-type three-phase full-bridge inverter 5 regenerative power bypass diode 8 inverter control circuit 9 capacitor 10 starting circuit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-268367 (JP, A) JP-A-63-95855 (JP, A) JP-A-4-21362 (JP, A) JP-A-4-42 54873 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H02P 6/08 H02M 7/48 H02P 7/63

Claims (5)

(57) [Claims] 1. A bridge rectifier circuit (2) having an AC power supply (1) as an input, a step-down chopper circuit (3) for stepping down a DC voltage obtained by the bridge rectifier circuit (2), and a step-down chopper circuit (3). ), A voltage-type bridge inverter (4) having a DC power supply as an input, a regenerative power bypass diode (5) reversely connected in parallel with a step-down chopper circuit (3), and an induced voltage of a motor (6). And an inverter control means (8) for supplying a switching command to the voltage-type bridge inverter (4) so as to make the power factor of the motor (6) substantially equal to one. 2. The inverter device for driving a motor according to claim 1, wherein a capacitor is further connected between output terminals of the step-down chopper circuit. 3. The inverter device for driving a motor according to claim 1, wherein the motor (6) is a brushless DC motor (6). 4. A switching command is supplied to operate the voltage-type bridge inverter (4) in a predetermined pattern at the time of starting, and an induced voltage larger than a predetermined value is applied to the brushless DC.
The inverter device for driving a motor according to claim 3, further comprising starting means (10) for operating the inverter control means (8) in response to the generation of the motor (6). 5. An inverter control means (8) comprising: a resistor voltage dividing circuit (8a) for detecting a phase voltage of a motor (6); an integrator (8b) having a phase voltage as input; (8c) for determining the
5. A logic circuit according to claim 1, further comprising: d); and a logic operation circuit (8e) for obtaining and outputting a switching command based on the positive / negative determination result supplied through the photocoupler (8d). Inverter for driving a motor.