JPH02269479A - Inverter device - Google Patents

Abstract

PURPOSE:To surely prevent a switching element of an inverter main circuit from being damaged with an overcurrent by applying a stop command signal to a controller from a voltage detector when an AC power source output is interrupted and applying a drive command signal to a timer. CONSTITUTION:A control power source 18 so provided as to supply voltages from both an AC power source 1 and a DC power source 8 for supplying a DC voltage to a timer 16 and a controller 15, and a voltage detector 14 for detecting the voltage of the power source 1 are provided. The detector 14 applies, when detecting the interruption of the AC power source, a drive command signal to the timer 16 based on it, and a stop command signal to the controller 15. After an inverter main circuit 9 is stopped, even if the voltage of the control power source is reduced and a malfunction signal is output from the controller, a smoothing capacitor is discharged. Thus, it can surely prevent a switching element from being damaged.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an inverter device that drives and controls a load via an inverter main circuit, and in particular, to prevent destruction of switching elements when power is cut off. The present invention relates to an inverter device having the function of

(Prior Art) This type of inverter device converts the output of an AC power supply into DC using a DC power supply circuit consisting of a rectifier circuit, a smoothing capacitor, etc., and then converts the output of the AC power into DC using a control circuit. The configuration is such that the AC is reconverted to AC and supplied to the load. In addition, when the AC power output is cut off, the control circuit simultaneously gives a stop signal to the switching elements in the inverter main circuit to turn them off, thereby preventing abnormal current from flowing into the switching elements in the inverter main circuit. It is designed to prevent it from flowing.

(Problem to be Solved by the Invention) However, in the conventional configuration as described above, the control circuit is supplied with power from an AC power source, so when the power is cut off, a stop signal is sent to the inverter main circuit, and after receiving the t
When the a-source lightning voltage drops, the stop signal cannot be held, so there is a possibility that an abnormal signal will be output. On the other hand, at this time, since the terminal voltage of the smoothing capacitor of the DC power supply circuit is still high, a large input terminal is applied to the inverter main circuit. Therefore, when an abnormal signal that short-circuits the circuit is applied to the switching element of the inverter main circuit, a large current from the smoothing capacitor flows through the switching element, which may lead to destruction.

The present invention has been made in view of the above circumstances, and its purpose is to stop the inverter main circuit when the AC power output is cut off, and then the output voltage of the control power source decreases and an abnormal signal is output from the control circuit. To provide an inverter device that can reliably prevent switching elements of an inverter main circuit from being destroyed due to overcurrent due to residual charge in a smoothing capacitor, even when the smoothing capacitor is overloaded.

[Structure of the Invention (Means for Solving the Problems) The present invention converts AC power output into DC using a DC power supply circuit consisting of a rectifier circuit and a smoothing capacitor, and then reconverts it into AC through a switching operation of an inverter main circuit. and a control circuit that is provided to control the switching operation of the inverter main circuit and forcibly stops the switching operation when a stop command signal is given, and the smoothing capacitor. a discharge circuit that selectively discharges the charge of the battery, a timer circuit that drives the discharge circuit to perform a discharge operation after a predetermined period of n and ν when a drive command signal is applied, and the AC power source and the DC power source. A control 72 that is provided so as to be supplied with power from both sides of the circuit and supplies one DC power source to the timer circuit and the control circuit! a power source circuit, and a voltage detection circuit that detects the voltage of the AC power supply, and when the voltage detection circuit detects cutoff of the AC power supply, it applies a drive command signal to the timer circuit and causes the control circuit to stop the voltage detection circuit. The feature is that it is configured to give a command signal.

(Function) When the voltage detection circuit detects interruption of the AC power supply, it provides a drive command signal to the timer circuit and a stop command signal to the control circuit based on this.

As a result, the control circuit gives a stop signal to the switching elements in the inverter main circuit to stop them, while the timer circuit gives a drive signal to the discharge circuit after a predetermined period of time has passed and the switching elements have stabilized. to quickly discharge the smoothing capacitor.

Therefore, even if the voltage of the control power supply drops after this and an abnormal signal is output from the control circuit, the switching element is reliably prevented from being destroyed because the charge in the switching capacitor has been discharged. .

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows an outline of the electrical configuration, where 1 is a three-phase AC power supply, 2 is a circuit breaker, and 3 is an electromagnetic contactor. 4
is a full-wave rectifier circuit made up of bridge-connected diodes.
DC power lines 5 and 6 are connected to each of the positive and negative output terminals. 7 is a smoothing capacitor connected between the DC power supply lines 5 and 6, which is connected to the full-wave rectifier circuit 4 and the DC power supply circuit 8.
It consists of 9 is the inverter main circuit connected between the DC power lines 5 and 6, which has a well-known configuration in which three pairs of power transistors, which are switching elements corresponding to three phases, are bridge-connected, and the output side has a load. Electric motor 1
0 is connected.

Reference numeral 11 denotes a discharge circuit, which includes a discharge resistor 12 and a forward bias thyristor 13 connected in series between DC power supply lines 5 and 61. In this case, the discharge circuit 11
When the trigger signal St is applied to the gate of the smoothing capacitor 7, the smoothing capacitor 7 becomes conductive and the charge of the smoothing capacitor 7 is rapidly discharged via the discharging resistor 12.

14 is a voltage detection circuit whose input terminal is connected to circuit breaker 2
It is connected to the AC type R1 via the AC power source 1 and outputs a stop command signal Sa and a drive command signal Sb when the voltage of the AC power supply 1 is detected, particularly when a cutoff state is detected. Reference numeral 15 denotes a control circuit that switches and drives the transistors of the inverter main circuit 9 and converts them into AC output. In particular, when a stop command signal Sa is given from the voltage detection circuit 14, a stop signal S is sent to the transistors of the inverter main circuit 9.
z, thereby turning off each transistor filter in the inverter main circuit 9. 16 is a timer circuit, which starts timer operation when the drive command signal SL+ is given from the voltage detection circuit 14, and after a predetermined time has elapsed, transmits the signal to the thyristor 13 of the discharge circuit 11 via the trigger circuit 17. The trigger signal St is given. Reference numeral 18 denotes a control power supply circuit, the input side of which is connected to the AC power supply 1 via the circuit breaker 2, and connected to the DC power supply line 5 via a reverse current blocking diode 19 and a voltage level adjustment circuit 20 in series. .6
connected between. As a result, the control power supply circuit 18
is supplied with power from both the AC power supply 1 and the DC power supply circuit 8,
One DC power source is supplied to the control circuit 15, timer circuit 16, and the like.

Next, the operation of this embodiment will be explained with reference to FIG. 2 showing the output waveforms of each part in FIG. 1.

First, when the DC power supply circuit 8 is supplied with power from the AC power supply 1, power is supplied to the inverter main circuit 9 through the full-wave rectifier circuit 4 and the smoothing capacitor 7. On the other hand, since the control circuit 15 is supplied with DC power from the control power supply circuit 18, it drives and controls the transistors of the inverter main circuit 9. As a result, the electric motor 10 is connected to the inverter main circuit 9.
A controlled three-phase alternating current power supply is applied to the motor, causing it to rotate.

When the output of the AC power supply 1 is cut off due to a failure or an accident (see FIG. 2(a), time to), the following operation is performed.

That is, the AC power supply voltage becomes zero, and in this state, a terminal voltage due to the charge charged in the smoothing capacitor 7 appears between the DC power supply lines 5 and 6 (see Fig. 2 (c), time 1).
+). On the other hand, when the voltage detection circuit 14 detects that the output of the AC power supply 1 is cut off, it gives a stop command signal Sa to the control circuit 15 based on this, and also sends a stop command signal Sa to the timer circuit 1.
The drive command signal sb is now given to 6. As a result, the control circuit 15 outputs a stop signal Sz to each transistor of the inverter main circuit 9 to control them to an off state. Further, the timer circuit 16 starts the timer operation, and when a predetermined time has elapsed (time t2), that is, after the transistors of the inverter main circuit 9 are in a stable off state, the discharge circuit 11 is activated via the trigger circuit 17. A trigger signal St is output to the thyristor 13. As a result, the charge in the .11 slipping capacitor 7 is rapidly discharged by the discharge circuit 11, and the input terminal of the inverter main circuit 9 is also rapidly reduced.

At this time, the control power supply circuit 18 is supplied with power from the smoothing capacitor 7 until the smoothing capacitor 7 is discharged (time tl to tz), and After being discharged, the output voltage gradually decreases as charging elements such as capacitors in the circuit are discharged (see FIG. 2(b), after time t2). Therefore, even if an abnormal signal is output from the control circuit 15 and applied to the inverter main circuit 9 after this, the input terminal of the inverter main circuit 9 is almost zero as described above, and its switching elements The power transistor is reliably prevented from being destroyed due to overcurrent.

It should be noted that the present invention is not limited to the embodiments described above, and may be implemented with appropriate modifications within the scope of the invention, for example, the load may be not only an electric motor but also other electrical equipment.

[Effects of the Invention] As explained above, according to the inverter device of the present invention, when the AC power output is cut off, the voltage detection circuit can give a stop command signal to the control circuit and give a drive command signal to the timer circuit. As a result, the control circuit gives a stop 1 signal to the switching elements of the inverter main circuit, and the timer circuit stops the charge on the smoothing capacitor after the switching elements of the inverter main circuit reach a stable stop state after a predetermined period of time has elapsed. Since we forced the discharge of
Unlike conventional methods, even if the output voltage of the control power supply circuit drops and an abnormal signal is output from the control circuit, no voltage is applied to the input side of the inverter main circuit, so the switching elements will not be destroyed by overcurrent. This has the excellent effect of reliably preventing such problems.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a schematic diagram of the electrical configuration, and FIG. 2 is an explanatory diagram showing temporal changes in voltage at various parts. In the drawing, 1 is an AC power supply, 2 is a circuit breaker, 4 is a rectifier circuit, 7 is a smoothing capacitor, 8 is a DC power supply circuit, 9 is an inverter main circuit, 10 is a motor (load), 11 is a discharge circuit, 12 is a discharge resistor, 13 is a cyrisk, 14 is a voltage detection circuit, 15 is a control circuit, 16 is a timer circuit, 18
8 is a control power supply circuit, 8 is a reverse current blocking diode, and 9 is a voltage level adjustment circuit.

Claims (1)

[Claims] 1. In an apparatus in which the output of an AC power source is converted to DC by a DC power circuit consisting of a rectifier circuit and a smoothing capacitor, and then reconverted to AC by a switching operation of an inverter main circuit to drive and control a load, the switching of the inverter main circuit a control circuit that is provided to control the operation and forcibly stops the switching operation when a stop command signal is given; a discharge circuit that selectively discharges the electric charge of the smoothing capacitor; and a drive command signal is given. Sometimes, a timer circuit is provided to drive the discharge circuit to perform a discharge operation after a predetermined period of time has elapsed, and a timer circuit is provided so as to be supplied with power from both the AC power supply and the DC power supply circuit, and supplies DC power to the timer circuit and the control circuit. a control power supply circuit that detects the voltage of the AC power supply; and a voltage detection circuit that detects the voltage of the AC power supply, and the voltage detection circuit supplies a drive command signal to the timer circuit when detecting cutoff of the AC power supply; An inverter device configured to give a stop command signal to a control circuit.