JPH0330324B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit switching device, and more particularly to a snubber circuit of a circuit switching device comprising a plurality of current self-interrupting type semiconductor elements connected in series.

Recently, advances in semiconductor technology have led to the development of self-interrupting semiconductor devices that can interrupt current using a gate signal, and gate turn-off thyristors (hereinafter referred to as GTO thyristors) and the like have been put into practical use as power control devices. Figure 1a and b show the configuration of a GTO thyristor.
A thyristor is a semiconductor device with a layered PNPN structure that can be turned on by a positive gate signal and turned off by a negative gate signal.

By the way, when such current self-interrupting type semiconductor elements are connected in series to form a circuit switching device, there is a problem that the voltage sharing between the series elements becomes unbalanced. Fig. 2 shows an electric circuit diagram of a circuit switchgear constructed by connecting GTO thyristors in series, and Figs. 3A to 3F show its operating waveform diagrams. In these figures, GTO ₁ and GTO ₂ are each GTO thyristor connected in series, which includes a resistor R ₁ and a capacitor.
A series circuit of C ₁ and a snubber circuit consisting of a series circuit of resistor R ₂ and capacitor C ₂ are connected in parallel. Also, i _G1 , i _G2 ; I _G1 , I _G2 ; V _G1 ,
V _G2 is the gate current and conduction current of GTO ₁ and GTO ₂ ,
is the terminal voltage.

In Figure 3, even when the same gate currents i _G1 and i _G2 are applied to each GTO thyristor, if there are variations in the turn-off characteristics of each GTO thyristor, in other words, the turn-off characteristics of GTO ₁ will be faster than that of GTO ₂ . This is illustrated by an example. GTO ₁ is GTO ₂
When it is turned off earlier, the terminal voltage V _G1 of GTO ₁ becomes temporarily high, as shown in Figure 3 (c).
In some cases, problems such as voltage damage to GTO ₁ may occur. Such voltage sharing problems are generally exacerbated not only by variations in the turn-off characteristics of individual GTO thyristors, but also by variations in the gate current given to each GTO thyristor. This is a major drawback when applied as an element to large-capacity devices such as chippers and inverters.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a circuit switching device that eliminates the drawbacks of the prior art described above and can improve voltage sharing during turn-off of each self-interrupting type semiconductor device connected in series.

According to the present invention, the object is to transfer the current of the unextinguished current self-interrupting semiconductor element to a snubber circuit when any one of the plurality of series-connected current self-interrupting semiconductor elements is first extinguished. The current in the self-interrupting semiconductor element, which has not yet been extinguished, is shunted so as to decrease without passing through the resistor.
When the plurality of series-connected current self-interrupting type semiconductor elements ignite the electric charge stored while the plurality of series-connected current self-interrupting type semiconductor elements are turned off, the current self-interruption occurs. This is achieved by providing a shunt capacitor that discharges through the resistor of the snubber circuit and the snubber circuit.

As a result, part of the current that flows through the snubber circuit of the current self-interrupting semiconductor element that turns off first flows through the shunt capacitor.
The current flowing through the current self-interrupting type semiconductor element, which turns off with a delay, is reduced, and the turn-off of this current self-interrupting type semiconductor element can be accelerated.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 4 is an electric circuit diagram of a circuit switching device according to an embodiment of the present invention, and FIGS. 5A to 5F are operation waveform diagrams thereof.

This example uses a resistor with diodes D ₁ and D ₂ connected in parallel to each GTO ₁ and GTO ₂ .
A snubber circuit is constructed by connecting R ₁ and R ₂ and capacitors C ₁ and C ₂ in series, and a shunt capacitor C is connected between the connection points of the resistor and the capacitor. The snubber circuit connected to GTO ₁ has its capacitor C ₁ side connected to the cathode of GTO ₁ , and the snubber circuit connected to GTO ₂ has its capacitor C ₂ side connected to the anode of GTO ₂ . has been done. Generally, the aforementioned snubber circuit is provided to suppress the rate of increase in the forward voltage that is reapplied when the GTO thyristor is turned off, and the diodes D ₁ and D ₂ are
When the GTO thyristor turns off, the resistances R ₁ and R ₂
It operates to short circuit the voltage drop that occurs in each
This further suppresses the rate of increase in the voltage reapplied to the GTO thyristor.

In the embodiment of the present invention configured in this manner, when GTO ₁ is turned off first, the current I _G2 flowing through GTO ₁ is transferred to the resistor R ₁ of the snubber circuit and the diode D ₁ as shown in FIG. The current is divided into the capacitor C ₁ and the shunt capacitor C through the parallel circuit (currents i _C1 , i _C ). Since the current iC2 of capacitor C1 flows through GTO ₂ , which turns off with a delay _{, the current flowing to GTO 2 is} a current reduced by the current ic shunted to shunt capacitor _C (capacitor _C1 and shunt capacitor C2). If the capacitance of C is made equal, the current flowing through GTO ₂ will be 1/1 of the original current.
2). At this time, the negative gate current of GTO ₂ has a current value that extinguishes the original current before decreasing, so the turn-off operation of GTO ₂ is accelerated, and as shown by the solid line in Fig. 5, It becomes possible to turn off GTO ₂ at approximately the same time as GTO ₁ , allowing good voltage sharing between GTO ₁ and GTO ₂ . Note that the broken line in FIG. 5 shows the operating waveform in the case of the conventional circuit without the shunt capacitor C, and it can be seen that the effect of the embodiment of the present invention shown in FIG. 4 is remarkable.

In addition, when the voltage charged in the shunt capacitor C causes an oscillation phenomenon through the wiring inductance and power supply of the circuit (not shown) due to the above operation, the reverse direction of the oscillation current flows through the cathode and resistor of GTO ₂ .
The current flows through the path of R ₂ , shunt capacitor C, resistor R ₁ , and the anode of GTO ₁ , and the peak value of this reverse current can be sufficiently suppressed.

Furthermore, the charge accumulated in the shunt capacitor C while GTO ₁ and GTO ₂ are turned off is
When GTO ₁ and GTO ₂ are turned on, these
The current will be discharged via GTO ₁ , GTO ₂ and resistors R ₁ , R ₂ , and the peak value of the current will be sufficiently suppressed by resistors R ₁ and R ₂ , and GTO ₁ ,
No overcurrent flows through GTO ₂ .

The operation of one embodiment of the present invention has been described above for the case where GTO ₁ turns off first.
The embodiment of the invention shown in the figure can similarly operate if GTO ₂ turns off first,
It is possible to speed up the turn-off operation of GTO thyristors that turn off with a delay without having to check the characteristics of two GTO thyristors to make connections, and it is possible to improve the voltage sharing at the time of turn-off of GTO thyristors connected in series. . Also, this embodiment is applicable to GTO ₁ or GTO ₂
At turn-off, the capacitors (C+C 2 ) and (C+C ₁ ) are connected to the capacitors C ₁ and _{C 2} of the respective snubber circuits.
Since the series circuits are connected in parallel, it also has the effect of further suppressing the rate of increase in the reapplied voltage to each GTO thyristor.

In addition to the above-mentioned GTO thyristor, a field effect thyristor (an element that turns on without a gate signal and turns off with a negative gate signal) or the like can be used as the current self-interrupting semiconductor element.

As described in detail above, according to the present invention, in a circuit switching device consisting of current self-interrupting semiconductor elements such as GTO thyristors connected in series, there is no need to check the characteristics of the elements before making connections, and there is no delay. This has the effect of speeding up the turn-off operation of the element that is turned off by turning it off, and making it possible to improve the voltage sharing when turning off each element.

[Brief explanation of the drawing]

Figures 1a and b are configuration diagrams of a GTO thyristor, Figure 2 is an electric circuit diagram of a conventional circuit switchgear configured by connecting GTO thyristors in series, and Figures 3-A.
FIG. 4 is an electric circuit diagram showing a circuit switching device according to an embodiment of the present invention, and FIGS. 5A to 5F are operation waveform diagrams thereof. GTO ₁ , GTO ₂ ...GTO thyristor, R ₁ , R ₂
... Resistor for snubber, C ... Shunt capacitor,
C ₁ , C ₂ ... Capacitor for snubber, D ₁ , D ₂ ...
Diode for Snatsuba.

Claims (1)

[Claims] 1. A snubber consisting of a plurality of series-connected current self-interrupting semiconductor devices that are turned on and off by a gate signal, and each of these current self-interrupting semiconductor devices is connected to a series circuit of a parallel body consisting of a diode and a resistor, and a capacitor. In a circuit switchgear in which circuits are connected in parallel, when one of the self-interrupting semiconductor elements is first extinguished, the current of the self-interrupting semiconductor element that is not extinguished is passed through the resistance of the snubber circuit. The current of the current self-interrupting type semiconductor device which has not yet been extinguished is shunted to decrease without causing the arc to be extinguished, and the electric charge accumulated while the plurality of series-connected current self-interrupting type semiconductor devices are turned off is removed. , a circuit opening/closing circuit comprising a shunt capacitor that discharges electricity through the resistors of the plurality of series-connected current self-interrupting semiconductor elements and the snubber circuit when the plurality of series-connected current self-interrupting semiconductor elements are ignited. Device.