JPS6349098Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a failure detection device for a gate turn-off thyristor that can be turned on and off with a gate, and in particular, by locating the failure detection part on the low voltage side, it is possible to apply parts with low withstand voltage. The present invention is intended to provide a failure detection device that has the following features.

Gate turn-off thyristors (hereinafter abbreviated as GTO), which can be turned on and off by a gate, are becoming increasingly high in voltage and capacity, and are used in pulse width modulation type uninterruptible power supplies.
Furthermore, they are being used in current source inverters, voltage source inverters, etc. as variable frequency power sources. As shown in FIG. 1, conventional methods for detecting such GTO failures include a light emitting diode 3, a phototransistor 3 ₂ , a resistor 3 ₃ , and a diode 3 ₄ connected in parallel between the anode and cathode of the GTO 1. Connect the detection device 3 and turn off the signal from the gate circuit mounted on this printed board.
When GTO1 is turned off using the gate signal,
With the main circuit power supply voltage applied between the anode and cathode of the GTO 1, the light emitting diode _{31 is ignited through the path of the resistor 33 → light emitting diode 31 , and} the output of the phototransistor ₃₂ is set to the "0" level. If so, the GTO is normal.On the other hand, if the GTO loses its forward blocking ability and remains conductive, the light emitting diode ₃₁ will not emit light when the OFF gate signal is sent. The output of the phototransistor ₃₂ remains at the "1" level. In this way, the condition that the output of the phototransistor ₃₂ continues to be at the "1" level is used to determine that the GTO has failed, but with this method, the failure detection device is placed on the main circuit side. Therefore, each part such as the light emitting diode ₃₁ must have a withstand voltage sufficient to withstand the power supply voltage of the hand circuit, which makes the device itself extremely difficult to use. What is more important is that specified failure detection cannot be performed unless the main circuit is energized.

The present invention has been devised in view of this point, and in particular, the present invention has a major feature in that a detection device is disposed on the low pressure side, and will be described in detail below based on the embodiment shown in FIG.

In the embodiment shown in Fig. 2, 4 is a rectifier circuit for ON gate, 5 is a rectifier circuit for OFF, 6 is a switching element for ON gate, and 7 is a switching element for OFF.
8 is a switching element for the gate, and 8 is a first failure detection circuit that operates when ON, which is the main part of the present application. As shown in the figure, this detection circuit 8 is mounted on a printed board on the low voltage side and includes a light emitting diode 8 ₁ -phototransistor. It is composed of 8 ₂ -resistor 8 ₃ -diode 8 ₄ . 9 is the second main part that operates when the other is OFF.
As shown in the figure, this circuit has a light emitting diode 9 mounted on a printed circuit board on the low voltage side.
₁ - phototransistor 9 ₂ - resistor 9 ₃ - diode 9 ₄ .

The operation of this embodiment configured as described above is explained in the third section.
To explain in detail with reference to the operation waveform diagram in the figure, first,
The detection method when the main circuit into which GTO1 is inserted is not energized will be described. A predetermined control power supply voltage is applied to the gate circuit etc. mounted on the printed board.
When a desired ON gate signal is given to the ON switching element 6, the rectifier circuit 4 → switching element 6 → GTO gate and cathode → rectifier circuit 4
Current flows through the path. If the gate-cathode of the GTO is at high impedance at the time of application of this ON gate signal, a G-K voltage is applied between the terminals of the light emitting diode ₈₁ of the first fault detection circuit 8, causing the light emitting diode ₈₁ to emit light. The diode emits light. When the diode 8 ₁ emits light in this way, the output of the phototransistor 8 ₂ becomes "0" level, and it is determined that the GTO is normal. Next, when a desired OFF gate signal is applied to the OFF switching element 7,
A current flows in the path of rectifier circuit 5 → GTO cathode and gate → switching element 7 → rectifier circuit, and if there is a high impedance between the gate and cathode of GTO at the time of application of this OFF gate signal, there will be a current between G and K. A voltage appears and the light emitting diode ₉₁ emits light. When the light emitting diode 9 ₁ emits light in this manner, the phototransistor 9 ₂ becomes conductive and its output becomes the "0" level, and it is determined from this detection signal that the GTO is normal. Figure 3 shows the above operation mode, and A in the figure is
The voltage appearing between the gate and cathode of the GTO is shown, and B shows the voltage waveform diagram of the detection signal output from the phototransistor. As is clear from these voltage waveform diagrams, if the GTO is normal, a predetermined voltage will appear between G and K of the GTO when the ON gate signal and OFF gate signal are applied, as shown in the waveform diagram before point _t . The detection signal is at the "0" level. For some reason, G-K of GTO
If a fault occurs due to a short circuit between the
Since the impedance between G and K is zero or close to zero at the time when the OFF gate signal is applied, the voltage between G and K becomes zero as shown after point _t1 in Figure 3, and the detection signal The level becomes "1".
In this way, under the condition that the detection signal is "1", GTO
This is to determine that there is a failure. The above explanation of the operation has been about the failure detection method when the main circuit is not energized, but even if the main circuit is energized, if the GTO is turned OFF during the specified ON-OFF control, for example by giving an OFF gate signal. , G- of GTO
The impedance between K increases and a voltage appears between the G and K, and the detection signal also goes to the "0" level.On the contrary, the ON gate signal is applied and the GTO is turned ON.
Then, a voltage will appear between G and K until the impedance between G and K decreases to approximately zero value, so the detection signal will also be at the "0" level and it will be determined that it is normal. , failures can be reliably detected even when the GTO is in constant operation.

As described above, in the present invention, since the failure detection device is disposed on the low voltage side to perform predetermined failure detection, various effects can be achieved as described below.

Since each part constituting the failure detection device can have a low pressure resistance, it is possible to realize a very cost-effective device.

Tests for the presence or absence of abnormalities can be performed without energizing the main circuit, which significantly reduces power consumption during testing.The fault detection circuit is configured for when the GTO is ON and OFF, so it detects faults with high accuracy. can be detected.

[Brief explanation of the drawing]

Fig. 1 is a specific circuit diagram showing a conventional fault detection device, Fig. 2 is a specific circuit diagram of a fault detection device showing an embodiment of the present invention, and Fig. 3 is a time chart showing its operation. . 1 is a gate turn-off thyristor, 4-5 is a rectifier circuit, 6-7 is a switching element, 8-9 is a failure detection circuit, 8 ₁ -9 ₁ is a light emitting diode, 8 ₂ -
9 ₂ is a phototransistor.

Claims (1)

[Scope of utility model registration request] A first rectifier circuit that rectifies the AC input power supply voltage, and a predetermined ON circuit provided on the DC output side of this circuit.
A first switching element that provides a gate signal through a gate-cathode path, a second rectifier circuit that rectifies the AC input power supply voltage, and a second rectifier circuit that is provided on the DC output side of this circuit and applies a predetermined OFF gate signal to the cathode.
a second switching element applied through the gate path; a first light emitting element that responds to the voltage between the gate and cathode when OFF; and a second light emitting element that responds to the voltage between the gate and cathode when ON; 1. A failure detection device for a gate turn-off thyristor, comprising first and second light receiving elements that output predetermined detection signals in response to the outputs of these light emitting elements.