JPS627781B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inverter power supply device that converts an AC voltage from an external AC power source into an AC voltage for driving a load to drive a load.

When controlling the drive of an AC motor,
2. Description of the Related Art Inverter power supply devices having an inverter circuit that converts an AC voltage from an external AC power source into an AC voltage for driving an AC motor at a desired voltage and frequency are widely used. In such an inverter power supply device, a transistor inverter circuit using large-capacity transistors is particularly suitable as a speed control means for an AC motor because large-capacity transistors have better responsiveness than other voltage control means.

However, the above-described transistor inverter circuit has a drawback that the large-capacity transistor may be destroyed if the power supply voltage supplied to the large-capacity transistor decreases. this is,
This is because when the voltage of the large-capacity transistor drive power source decreases, the drive current of the large-capacity transistor decreases, and as a result, the on-resistance increases, resulting in thermal destruction of the large-capacity transistor.

Therefore, in conventional devices, in order to protect the main circuit transistors from the above thermal damage, if the AC voltage supplied from the external AC power supply to the transistor inverter circuit falls below a predetermined value, a power outage accident may occur, especially in the external AC power supply. In such a case, the main circuit transistor will be disconnected immediately.

FIG. 1 shows a conventional example of an inverter power supply device employing the above-described method.

In the figure, the conventional device uses an AC voltage supplied from an external AC power source 10 to an induction motor 12.
An inverter circuit 14 that converts the AC voltage for driving into an AC voltage for driving is provided. It is composed of an inverter 18 that converts the voltage into voltage. The inverter 18 uses voltage control large capacity transistors (main circuit transistors) as voltage control elements, and a base control signal 100 is supplied from a base control circuit 20 to each base of each of these main circuit transistors. The inverter 18 is the base control circuit 20
The motor 12 can be driven and controlled by a base control signal 100 from the base control signal 100 . A voltage command 202 and a frequency (speed) command 204 based on an external voltage speed command 200 are supplied to the base control circuit 20 from a voltage command circuit 24 and a frequency (speed) command circuit 26 of the voltage speed command circuit 22, respectively. The base control circuit 20 sends a voltage command 20 to the base of each main circuit transistor of the inverter 18.
2. Base control signal 10 according to speed command 204
0 can be supplied.

Further, the AC voltage supplied from the external AC power supply 10 to the converter 16 is constantly monitored by a voltage abnormality detection circuit 28, and the voltage abnormality detection circuit 28 performs base control when the voltage of the external AC power supply 10 falls below a predetermined value. A voltage abnormality signal 300 can be provided to circuit 20 . The base control circuit 20 can control the main circuit transistor of the inverter 18 to stop immediately when the voltage abnormality signal 300 is supplied from the voltage abnormality detection circuit 28.

The conventional example shown in FIG. 1 has the above configuration, and its operation will be explained below.

When the external AC power supply 10 is turned on, the device starts up and receives voltage command signals 2 from the voltage command circuit 24 and frequency (speed) command circuit 26 of the voltage speed command circuit 22 to which the voltage speed command signal 200 has been applied.
02, a frequency (speed) command signal 204 is supplied to the base control circuit 20, and a base control signal is supplied from the base control circuit 20 to each main circuit transistor of the inverter 18.

The AC voltage supplied from the external AC power supply 10 is converted into DC by the converter 16 and supplied to the inverter 18 . Since the base control signal 100 is supplied from the base control circuit 20 to each main circuit transistor of the inverter 18, the inverter 18 uses the base control signal 100 of the DC voltage supplied from the converter 16 to drive the motor 12. A conversion action into an alternating voltage is performed.

The drive of the motor 12 is controlled by the AC voltage for driving the motor 12 obtained as described above, and a load connected to the rotating shaft of the motor 12 is driven.

In the operating state obtained in this manner, if the AC voltage supplied to the converter 16 drops due to an accident occurring in the external AC power supply 10, etc., the voltage abnormality detection circuit 28 detects this voltage abnormality. and sends a voltage abnormality signal 3 to the base control circuit 20.
Supply 00. When the base control circuit 20 receives the voltage abnormality signal 300 from the voltage abnormality detection circuit 28, it immediately disconnects the bases of each main circuit transistor of the inverter 18.

Inverter 1 whose base was cut off in this way
Each of the 8 main circuit transistors is protected from destructive accidents as described above.

When the output voltage of the external AC power supply 10 returns to normal, the voltage abnormality detection circuit 28 outputs the voltage abnormality signal 300 that was previously supplied to the base control circuit 20.
supply will be stopped. Therefore, the base control circuit 20 resumes supplying the base control signal 100 according to the voltage command signal 202 and frequency (speed) command signal 204 of the voltage speed command circuit 22, which is the same as in the original normal state, so that the device can return to the operating state described above.

As described above, in the conventional example shown in FIG. 1, the main circuit transistor of the transistor inverter 18 is protected by immediately turning off the main circuit transistor in the event of an accident in the external AC power supply 10, but continuous operation is required. The disadvantage is that it is not possible to connect a load to the motor 12. That is, in the conventional example shown in FIG. 1, when a power outage accident occurs in the external AC power supply 10, the main circuit transistor of the inverter 18 is immediately cut off, so the motor 12 is controlled to stop every time a momentary power outage occurs. It is from.

In particular, in the conventional example shown in FIG.
Since the current is supplied to the base of the main circuit transistor of the inverter 18, there is a risk that an overcurrent may flow to the main circuit transistor of the inverter 18.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide an inverter power supply device suitable for drive control of a load that requires continuous operation.

To achieve the above object, the present invention comprises a converter that converts an AC voltage from an external AC power source into a DC voltage, and an inverter including a main circuit transistor that converts the DC voltage from the converter into an AC voltage for driving a load. an inverter circuit, a base control circuit that performs base control of the main circuit transistor of the inverter, and a voltage speed command circuit that includes a voltage command circuit that supplies a voltage command to the base control circuit;
and a voltage abnormality detection circuit that supplies a voltage abnormality signal to the base control circuit when the external AC power supply voltage falls below a predetermined value. In an inverter drive control device that performs stop control of main circuit transistors, the base control circuit is
A zero voltage command is immediately generated when a voltage abnormality signal is supplied from the voltage abnormality detection circuit, and a return voltage command whose command value gradually increases when the voltage abnormality signal from the voltage abnormality detection circuit stops is generated. An abnormal voltage command generator consisting of a charging/discharging capacitor, a discharging resistor for generating a zero voltage command, and a charging resistor for generating a return voltage command, and a voltage command circuit and an abnormal voltage command generator, respectively. This includes an analog small priority circuit that compares the voltage commands and selects the voltage command with the lower command value, and prevents excessive load-driving AC current from flowing into the inverter's main circuit transistors when a momentary power failure returns. It is characterized by

Preferred embodiments of the present invention will be described below based on the drawings.

FIG. 2 shows a preferred embodiment of the present invention, and the same members as those in the conventional example shown in FIG.

In FIG. 2, the base control circuit 20 consists of an input section 20a and a control section 20b, and the input section 20a of the base control circuit 20 is connected to a voltage abnormality detection circuit 28.
An abnormal voltage command generator 30 is supplied with a voltage abnormality signal 300 from the voltage command circuit 24, a voltage command 202 from the voltage command circuit 24, and a voltage speed command 302 from the abnormal voltage command generator 30.
and an analog small priority circuit 32 that supplies voltage command 400 to voltage command 400.

The abnormal voltage command generation circuit 30 includes an emitter-grounded transistor 34 whose base is supplied with the voltage abnormality signal 300 from the voltage abnormality detection circuit 28, and a discharge resistor 36 having a relatively small resistance value connected to the collector of the transistor 34. , a charging/discharging capacitor 38 connected between the output side of the resistor 36 and the emitter of the transistor 34, and a charging resistor 40 connected between the output side of the resistor 36 and the power supply and set to a relatively high resistance value. , is composed of.

Further, the analog small priority circuit 32 includes a non-inverting OP amplifier (operational amplifier) 42a to which the voltage command 302 is supplied from the abnormal voltage command generator 30, and a non-inverting OP amplifier (operational amplifier) 42a to which the voltage command 202 is supplied from the voltage command circuit 24. Inverting OP amplifier 42b and each OP amplifier 42
It is composed of diodes 44a and 44b whose cathodes are connected to the outputs of diodes 44a and 42b. This analog small priority circuit 32 is connected to each OP amplifier 42.
The voltage generated at the negative inputs of a and 42b is set as the voltage command 40
0 to the control unit 20b, and the control unit 20b can supply the base control signal 100 according to the voltage command 400 to each main circuit transistor of the inverter 18.

Incidentally, a DC voltage V _DD is supplied to the analog low priority circuit 32 from a power supply via a resistor 46 .

A preferred embodiment of the present invention has the above configuration,
The effect will be explained below.

First, the normal operating state of the device will be explained. In the normal operating state of the device, the voltage abnormality signal 300 from the voltage abnormality detection circuit 28 is not supplied to the base of the transistor 34, so the transistor 34 is in the off state, and therefore the positive input of the OP amplifier 42a is _VDD. Since the OP amplifier 42a is non-inverting, the negative input of the OP amplifier 42a becomes _VDD .

Further, the voltage speed command 20 from the voltage command circuit 24
The negative input of the OP amplifier 42b to which 2 is supplied is
Since the OP amplifier 42b is non-inverting, the analog small priority circuit 3 has the voltage value of the voltage speed command 202.
The voltage at the output terminal 32a of No. 2 has a small voltage value after all.
The negative input potential of the OP amplifier 42b, ie, the voltage command 202, becomes the voltage command 202, and the voltage speed command 400 supplied from the analog small priority circuit 32 to the control unit 20b becomes the voltage command 202.

As described above, under normal operating conditions, the embodiment shown in FIG. 2 can perform the same operations as the embodiment shown in FIG.

Next, a case where a momentary power outage occurs in the external AC power supply 10 will be described. When a momentary power outage occurs in the external AC power supply 10 and its output voltage drops, a voltage abnormality signal 300 is supplied from the voltage abnormality detection circuit 28 to the base of the transistor 34, and the transistor 34 is turned on. Then, the charge accumulated in the capacitor 38 is rapidly discharged through the resistor 36 having a small resistance value, so that the negative input voltage of the OP amplifier 42a rapidly decreases.

If the power outage continues at this time, the resistance value of the resistor 36 is set to a small value and the resistance value of the resistor 40 is set to a high value, so that the positive input voltage of the OP amplifier 42a becomes almost zero potential. OP like this
When the negative input of the amplifier 42a becomes zero potential, it means that the zero voltage command 302 is supplied to the input of the OP amplifier 42a, so the zero voltage command 302 is sent from the output end 32a of the analog small priority circuit 32 to the control unit 20b.
is preferentially supplied as the voltage command 400. At this time, the base control circuit 20 controls the main circuit transistor of the inverter 18 to stop, and the inverter operation of the device is controlled to stop.

However, it is rare for the device to stop as described above, and instantaneous power outage accidents usually pose a problem. When a momentary power outage accident occurs in the external AC power supply 10, the external AC power supply 10
It returns in the middle of the discharge of 8. At this time, the voltage abnormality detection signal 300 is no longer supplied to the base of the transistor 34, so the transistor 34 is turned off again, and charge is accumulated in the capacitor 38 via the resistor 40 with a large resistance value, so that the voltage across the capacitor 38 increases. gradually rises. The voltage across the capacitor 38 that gradually increases in this way is
It is supplied to the OP amplifier 42a as a return voltage command 302, and when the voltage value of the return voltage command 302 is lower than the voltage value of the voltage command 202, the voltage command 400 is supplied.
The signal is supplied to the control unit 20b as a signal. Therefore,
Since the base control circuit 20 performs base control of the main circuit transistor of the inverter 18 in accordance with the recovery voltage command 302, the rotation of the motor 12 is gradually recovered. In this way, the voltage value of the return voltage command 302 gradually returns, and after the return voltage command 302 and the voltage command 202 become the same voltage value, the voltage command 202 has a lower voltage value, so the analog The voltage command 400 supplied from the small priority circuit 32 to the control unit 20b becomes the voltage command 202, and normal operation is performed.

As explained above, according to this embodiment, when a power outage accident occurs in the external AC power supply 10, the capacitor 38
Since the inverter action of the inverter 18 is rapidly controlled to stop due to the discharge, the main circuit transistor 18 of the inverter 18 can be protected in the same manner as in the conventional example shown in FIG. Furthermore, according to this embodiment, when a momentary power outage occurs in the external AC power supply 10, the discharging of the capacitor 38, which was once started due to the power outage, is stopped in the middle of discharging the capacitor 38, and the charging of the capacitor 38 is slowed down by the resistor 40. The motor is charged and the voltage command rises slowly, so even if there is a slight difference between the motor speed and the inverter output frequency, no overcurrent flows to the main circuit transistor, and steady operation can be resumed slowly. .

Therefore, according to this embodiment, it is possible to provide an inverter power supply device suitable for drive control of an AC motor that drives a load that requires continuous operation.

In the embodiment shown in FIG. 2, desired start-up control characteristics of the motor 12 can be obtained by changing the resistance value of the charging resistor 40 depending on the start-up condition of the shaft load of the motor 12.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a conventional example of an inverter power supply device, and Fig. 2 is a circuit diagram showing a preferred embodiment of the present invention.
10 is an external AC power supply, 12 is an induction motor, 14 is an inverter circuit, 16 is a converter,
18 is a transistor inverter, 20 is a base control circuit, 22 is a voltage speed command circuit, 24 is a voltage command circuit, 28 is a voltage abnormality detection circuit, 30 is an abnormality voltage command generator, 32 is an analog small priority circuit, 3
6 is a discharging resistor, 38 is a charging/discharging capacitor, and 40 is a charging resistor.

Claims (1)

[Claims] 1. An inverter circuit consisting of an inverter including a converter that converts an AC voltage from an external AC power supply into a DC voltage, and a main circuit transistor that converts the DC voltage from the converter into an AC voltage for driving a load, and a main circuit transistor of the inverter. A base control circuit that performs base control; a voltage speed command circuit that includes a voltage command circuit that supplies a voltage command to the base control circuit; An inverter power supply device comprising: a voltage abnormality detection circuit that supplies a voltage abnormality; Charging and discharging to generate a return voltage command that immediately generates a zero voltage command when a voltage abnormality signal is detected from the detection circuit and gradually increases the command value when the voltage abnormality signal from the voltage abnormality detection circuit stops. An abnormal voltage command generator including a capacitor, a discharging resistor for generating a zero voltage command, and a charging resistor for generating a return voltage command, and voltages supplied from the voltage command circuit and the abnormal voltage command generator, respectively. It includes an analog small priority circuit that compares the commands and selects the voltage command with the lower command value, and is characterized by preventing excessive load drive current from flowing through the inverter's main circuit transistors when a momentary power failure returns. Inverter power supply.