JPH0295196A - Controller for inverter device - Google Patents

Abstract

PURPOSE:To eliminate the need for the annexation of a power supply for emergency by giving the control power supply of an inverter control circuit from an AC power at all times, and said control power supply from the DC power of an inverter device when service interruption is detected. CONSTITUTION:The control power supply of an inverter control circuit 21 is given from an AC power 2 at all times through a control power circuit 18 and a power supply changeover circuit 19, and afforded from the DC powers 13, 14 of an inverter device 5 by changing over connection from the AC power of the power supply changeover circuit 19 to a DC power when a service interruption detector 17 detects service interruption. The output frequency of an inverter main circuit 16 is lowered at the same time, and the inverter device is controlled. Accordingly, the control power supply is acquired by the regenerative power of a motor 6 during a time when the motor 6 is stopped, and the control power supply is obtained without annexing a power supply for emergency when service interruption or trouble in a short time is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a control device for an inverter device for variable speed control of an electric motor.

(Prior Art) Conventionally, this type of inverter device converts AC power into DC power using a rectifier circuit and a smoothing capacitor, converts this DC power back into AC power using the inverter main circuit, and supplies the AC power to the motor. This inverter main circuit is configured to be controlled to a set output frequency by being given a control signal such as a PWM system by a control device.

(Problem to be Solved by the Invention) However, although the above-mentioned conventional system works well during normal operation, when a power outage occurs, for example, the power to the control device is lost, and the motor starts to rotate due to inertia. There was a problem in that even if the power was restored while the engine was running, it would not be possible to restart the engine until it stopped. Furthermore, if the electromagnetic contactor trips due to a failure or the like other than a power outage, the power to the control device is similarly cut off, and therefore, there is a problem in that the control device cannot display the failure state.

To solve the above problem, for example, by installing an emergency power source in advance,
Is it possible to switch to this emergency power source when the power to the control device is cut off due to a power outage, failure, etc.?Providing such an emergency power source would increase the cost significantly. This was a new problem.

The present invention has been made in view of the above circumstances, and its purpose is to provide an inverter device that can provide control power without installing an emergency power source even in the event of a short power outage or a failure other than a power outage. to provide control equipment.

[Structure of the Invention] (Means for Solving the Problems) A control device for an inverter device of the present invention obtains a DC power source from an AC power source through a rectifying circuit and a smoothing capacitor, and converts this DC power source into an AC power source using an inverter main circuit. In an inverter device configured to convert power into power and supply it to an electric motor, a power outage detection circuit is provided to detect a power outage of the AC power source,
A control power supply circuit for obtaining a control power supply is provided, and a power supply switching circuit is provided which always connects the AC power supply to the control power supply circuit and switches to connect the DC power supply when the power failure detection circuit detects a power failure. , an inverter main circuit that is supplied with control power from the control power supply circuit and controls the inverter main circuit to always maintain a set output frequency, and when the power failure detection circuit detects a power failure, controls the inverter main circuit to lower the output frequency; It has characteristics where it is installed.

(Function) According to the control device for an inverter device of the present invention, the control power for the inverter control circuit is always supplied from the AC power supply via the control power supply circuit and the power supply switching circuit, and the power failure detection circuit When a power outage is detected, the power supply switching circuit switches the connection from the AC power source to the DC power source, so that the power is supplied from the DC power source of the inverter device, and at the same time, the output frequency of the inverter main circuit is reduced to perform control. The regenerated power provides control power until the motor stops.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

First, in FIG. 2 showing the overall configuration, 1 is a main circuit connected to, for example, a three-phase AC power supply 2, and a circuit breaker 3 and an electromagnetic contact are connected to this main circuit bus 1a to the IC in order from the power supply side. A container 4 is interposed. Reference numeral 5 denotes an inverter device connected to the main circuit 1, and a three-phase induction motor 6 serving as an electric motor is connected to the output side of this inverter device. 7 is a control device that controls the inverter device 5 as described later, and its control power input terminal 7a is connected to the main circuit bus 1a between the circuit breaker 3 and the electromagnetic contactor 4 of the main circuit 1. Connected to IC. Reference numeral 8 denotes a failure detection circuit disposed within the control device 7, and the contact portion 9a of this circuit is turned off by the excitation coil 9 when a failure occurs on the load side. 10 is the electromagnetic contactor 4 and a normally open contact portion 1, which will be described later.
This is an excitation coil that acts on 0a. 11 is an on/off circuit in which a normally open on switch 11a and a normally closed off switch llb are connected in series;
The above-mentioned normally open contact portion 10a is connected in parallel with la. The contact portion 9a of the on-off circuit 11° failure detection circuit 8 and the excitation coil 10 are connected in series between the main circuit buses 1a, lc to which the control power input terminals of the control device 7 are connected. has been done.

Next, according to FIG. 1, the configuration of the inverter device 5 and its control device 7 will be described in detail. First, in the inverter device 5, 12 is a full-wave rectifier circuit formed by bridge-connecting diodes, the main circuit bus 1a to IC are connected to this AC input terminal, and the DC power supply line 13, 14 is connected to the DC output terminal. is connected. 15 is a smoothing capacitor, which is connected between DC power lines 13 and 14. 1
Reference numeral 6 denotes an inverter main circuit, the input side of which is connected to DC power supply lines 13 and 14, and the output side connected to the three-phase induction motor 6 described above. This inverter main circuit 16 is made up of, for example, six transistors connected in a bridge, and each transistor is switched by a PWM type shade to generate three-phase alternating current with controlled frequency and voltage. Next, in the control device 7, 17 is a power failure detection circuit whose input terminal is connected to the main circuit bus 1a to the IC between the inverter device 5 and the electromagnetic contactor 4,
It detects a power outage of the AC power supply 2 and outputs a power outage detection signal Sa. Reference numeral 18 denotes a control power supply circuit, which is connected to various circuits within the control device 5 to supply control power thereto, and its input terminal is connected to the power supply switching circuit 19.

This power supply switching circuit 19 has two sets of switchable input terminals a.
, b and a control input terminal C connected to the power failure detection circuit 17
The input terminal a is connected to the aforementioned control power input terminal 7a via the rectifier circuit 20, and the input terminal a is connected between the DC power lines 13 and 14 of the inverter device 5. In this case, the input terminal a side of the power supply switching circuit 19 is always connected to the output side, that is, the control power supply circuit 18.
When the above-mentioned power failure detection signal Sa is applied to the control input terminal C, only the input terminal 1 is connected. 2
1 is an inverter control circuit, which is configured as described below. That is, 22 is a frequency setting circuit consisting of a variable resistor, which sets the output frequency of the inverter device 5, and outputs a frequency setting signal Sb with a set value as a voltage value. 23 is an acceleration/deceleration control circuit, which has two input terminals a and b, and is normally connected to the frequency setting circuit 22 connected to input terminal a.
It outputs a signal for adjusting the acceleration/deceleration time according to the frequency setting signal sb from the inverter main circuit 16, and when the power failure detection signal Sa from the power failure detection circuit 17 connected to the input terminal S is given, the output frequency of the inverter main circuit 16 is changed. It is designed to output a signal to lower the temperature. 24 is a voltage/frequency control circuit whose input end is connected to the above-mentioned acceleration/deceleration control circuit 23, and whose output side is connected to the inverter main circuit 16 via the base drive circuit 25; Based on the signal from 23, a PWM signal Sc for switching the inverter main circuit 16 is output.

Next, the operation of this embodiment will be described.

First, when the on switch Ila of the on/off circuit 11 is turned on to start operation of the three-phase induction motor 6, the power supply voltage from the AC power supply 2 via the circuit breaker 3 and the main circuit buses 1a and lc is controlled. It is applied to the control power input terminal 7a of the device 7, and the on/off circuit 11. It is applied to a series circuit of the normally closed contact portion 9a of the failure detection circuit 8 and the exciting coil 10.

By energizing the excitation coil 10, the normally open contact portion 10a of the on-off circuit 11 is turned on, and the excitation coil 10 is turned on.
0 is maintained, the electromagnetic contactor 4 is turned on, and the power supply voltage of the AC power supply 2 is applied to the inverter device 5.

When power is supplied to the inverter device 5 and the control device 7 as described above, in the inverter device 5, the three-phase power supply voltage from the AC power source 2 is converted to a DC power source by the full-wave rectifier circuit 12 and the smoothing capacitor 5. The converted DC power is supplied to the inverter main circuit 16 via DC power lines 13 and 14. On the other hand, in the control device 7,
The single-phase power supply voltage from the AC power supply 2 applied to the control type source input terminal 7a is converted into a DC power supply via the rectifier circuit 20, and then becomes the control power supply via the power supply switching circuit 19 and the control power supply circuit 18. The signal is applied to the inverter control circuit 21 and other circuits. This causes the inverter control circuit 21 to provide a control signal to the inverter main circuit 16 as described below. That is, the acceleration/deceleration control circuit 23
Based on the frequency setting signal Sb given from the frequency setting circuit 22, outputs a voltage signal so as to increase the set output frequency at a predetermined rate. In response to this voltage signal, the voltage/frequency control circuit 24 synthesizes voltage and frequency command values as a PWM signal Sc, and supplies this to the inverter main circuit 16 via the base drive circuit 25. As a result, the inverter main circuit 16 outputs three-phase alternating current controlled to the set output frequency, and the three-phase induction motor 6 starts rotating and performs steady operation at a rotation speed corresponding to the set output frequency. state.

Next, we will discuss the case where a failure occurs on the load side and steady operation cannot be continued. That is, due to this failure,
When the normally closed contact section 9a of the failure detection circuit 8 is turned off by the excitation coil 9, the excitation coil 10 is cut off, thereby turning off both the electromagnetic contactor 4 and the normally open contact section 10a of the on/off circuit 11. Ru. As a result, the AC power source 2 is turned off to the inverter device 5, but the control device 7 continues to receive the power supply voltage from the AC power source 2 to the control power input terminal 7a, which causes a display (not shown) to appear. The device will now display a failure message.

Next, unlike the above case, a case will be described in which a power outage occurs in the AC power supply 2 during steady operation.

That is, when a power outage occurs, the power outage detection circuit 17 first detects this and provides a power outage detection signal Sa to the power supply switching circuit 19 and the acceleration/deceleration control circuit 23. As a result, the power supply switching circuit 19 switches and connects the control power supply circuit 18 on the output side to the input terminal side, and transfers the terminal voltage of the smoothing capacitor 15 remaining between the DC power supply lines 13 and 14 to the power supply side. It will be supplied as On the other hand, in the inverter control circuit 21 supplied with control power by this switched power supply, in response to the input of the power failure detection signal Sa, the acceleration/deceleration control circuit 23 adjusts the voltage so that the output frequency is lower than the set output frequency. The signal is lowered and given to the voltage/frequency control circuit 24. As a result, the output frequency of the inverter main circuit 16 is reduced, and the three-phase induction motor 6 is controlled to rapidly reduce its rotational speed. As a result, the three-phase induction motor 6 enters a regenerative braking state, so that the regenerated power is charged to the smoothing capacitor 15 via the inverter main circuit 16. Therefore, the three-phase induction motor 6
Since the control power supply to the control device 7 is secured while the regenerated power is being obtained, the inverter control circuit 21 can continue to control the three-phase induction motor 6 while decreasing the output frequency again. In such a state, when the power is restored, the power failure detection signal Sa of the power failure detection circuit 17 disappears, and the power supply switching circuit 19 switches to the control power supply circuit 18.
is switched to the input terminal a side again to supply the power voltage from the AC power supply 2, and the inverter control circuit 21 changes its output frequency from the output frequency before power restoration to the set output frequency again. Three-phase induction motor 6
The rotational speed of the engine will be increased to control it to a steady state of operation.

Note that if the power is restored after the power outage is long and the rotation of the three-phase induction motor 6 has stopped, restarting is performed in the same manner as when starting.

As described above, in this embodiment, the power supply switching circuit 19 is connected to the control power supply circuit 18 so as to always supply power from the AC power supply 2, and provides the power failure detection signal Sa from the power failure detection circuit 17. When the DC power supply line 13.14 is detected, the smoothing capacitor 15 is connected to supply power through the DC power lines 13 and 14, and at this time, the inverter control circuit 21 transmits its output frequency to the inverter main circuit 16 to detect a power outage. The configuration is such that control is performed to decrease the signal Sa. As a result, even if a failure occurs on the load side of the inverter device 5 and the electromagnetic contactor 3 is turned off, the control device 7
Since power is obtained from the AC power supply 2, a failure can be indicated using that power supply. Also, AC power supply 2
In the event of a power outage, control power can be obtained using the regenerated power of the three-phase induction motor 6, and in the event of a momentary power outage, the power will be restored without waiting for the three-phase induction motor 6 to stop when the power is restored. It becomes possible to control from the current state to a steady state of operation.

Therefore, unlike the conventional method, a control power source at the time of failure or momentary power outage can be obtained without adding an emergency power source, that is, without increasing costs.

It should be noted that the present invention is not limited to the embodiments described above and shown in the drawings, and it goes without saying that it can be implemented with appropriate modifications within the scope of the invention.

[Effects of the Invention] As explained above, according to the control device for an inverter device of the present invention, the following effects can be obtained.

That is, the control power of the inverter control circuit is always supplied from the AC power supply via the control power supply circuit and the power supply switching circuit, and is supplied from the DC power supply of the inverter device based on the power failure detection of the power failure detection circuit. At the same time, the output frequency of the inverter main circuit is controlled to be lowered. Thereby, even if a failure occurs on the load side, the inverter control circuit can display the failure without cutting off the control power supply. Also, in the event of a power outage,
Since the inverter main circuit can be controlled while obtaining control power from the regenerated electric power of the electric motor, if the electric power is restored before the electric motor is stopped, the electric motor can be restarted from that state. Therefore, unlike the prior art, a control power source for failures and short-term power outages can be obtained without adding an emergency power source, that is, without increasing costs.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, with FIG. 1 being an electrical configuration diagram showing details of an inverter device and a control device, and FIG. 2 being an electrical configuration diagram showing the overall outline. In the drawing, 2 is an AC power supply, 4 is an electromagnetic contactor, 5 is an inverter device, 6 is a three-phase induction motor (motor), 7 is a control device, 8 is a failure detection circuit, 10 is an exciting coil, 11 is an on/off circuit, 12 is a rectifier circuit, 13.1-4- is a DC power line, 15 is a smoothing capacitor, 16 is an inverter main circuit,
17 is a power failure detection circuit, 18 is a control power supply circuit, 19 is a power supply switching circuit, and 21 is an inverter control circuit. Applicant: Toshiba Corporation

Claims (1)

[Claims] 1. In an inverter device that obtains DC power from an AC power source through a rectifier circuit and a smoothing capacitor, converts this DC power into AC power by an inverter main circuit, and supplies the converted AC power to a motor, the power outage of the AC power source is prevented. A power failure detection circuit for detecting a power failure, a control power supply circuit for obtaining a control power supply,
A power supply switching circuit that normally connects the AC power supply to the control power supply circuit and switches to connect the DC power supply when the power failure detection circuit detects a power outage; A control device for an inverter device, comprising: an inverter control circuit that normally controls a main circuit to a set output frequency, and controls the output frequency to be lowered when the power failure detection circuit detects a power failure.