JPS636916A - High voltage current interrupting circuit - Google Patents

Abstract

PURPOSE:To prevent the overvoltage destruction of an element with low loss by connecting a voltage clamp circuit having a lower clamp voltage than the dielectric strength of the element in parallel with each element in the current interruption circuit where snubber circuits suppressing the rate of rise of voltage at extinction are connected in parallel. CONSTITUTION:The clamp circuit having a lower voltage than the dielectric voltage of the element is connected in parallel with each element in the current interruption circuit where each snubber circuit suppressing rate of rise of voltage at extinction each comprising diodes 9,10, capacitors 12,13 and resistors 17,18 are connected in parallel with the self-extincton type semiconductor elements connected in series. Thus, the overvoltage destruction of the element due to the voltage unbalanced sharing caused by the variation of the turn-off time of the self-extinction type semiconductor elements connected in series is prevented with a low loss.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a high-voltage current cutoff circuit constructed by connecting all self-extinguishing semiconductor elements in series.

[Conventional technology]

As this type of t-flow cutoff circuit, a chopper circuit shown in FIG. 4 has been known for 1iHJ. As shown by the dashed line in the figure, GTO thyristor 3.4, which is one of the self-extinguishing semiconductor elements, is connected in series to form diode 9.
．． A snubber circuit consisting of lO, capacitors 12 and 13, resistors t'y and is, and DC voltage dividing resistors 22 and 23t are connected in parallel with respective GTO thyristors 3 and 4. In this chopper circuit, GTO thyristor 3.4
While G is on and load current imt is flowing
When the TO thyristors 3 and 4 are turned off, the next time the anode current II l i2 of the GTO thyristors 3 and 4, the current 1g1 r '82 of the snubber capacitor 12.13, and the voltage V1 of the snubber capacitor 12 and 13 are set. V2 Each waveform of the current j of the current cutoff circuit shown by the dashed line is
As shown in the figure. In the same figure, GTO thyristors 3 and 4
It is assumed that the arc does not extinguish at the same time, and there is a difference in arc extinguishing time by Δt. That is, the GTO thyristor 4 has a high resistance at time Nta and commutates the 7 node current to the snubber circuit,
The GTO thyristor 3 operates in a similar manner at time tb determined after the Δin. At time tc, the sum of the voltages of the snubber capacitor 12 and 13, that is, the voltage vl + v of this tt current cutoff circuit, becomes equal to the voltage Ed of the snubber capacitor 14 in FIG. 4, and the snubber diode 11 is turned on.
From then on, the current in this current cutoff circuit is commutated to the snubber capacitor 14 in FIG. The current l becomes zero. Snubber conditioner/su12 at time td
and 13, that is, the anode voltages V and V of GTO thyristors 3 and 4 are not equal, and vl<
It becomes v2. this is.

This is due to the difference Δt between the extinguishing times of the GTO thyristors 3 and 4, and the difference voltage between Vl and V is given by the following equation with the capacity t'tc of the snubber capacitor 12.13 as follows.

In other words, the snubber capacitor 12 at time td is proportional to the difference Δt between the extinguishing times of the GTO thyristors 3 and 4.
and 13 voltage difference E6 increases, and the GTO which extinguished first
The voltage of the thyristor 4 at time td increases by 7 times. This voltage V! If is less than the withstand voltage of GTO thyristor 4, GTO thyristor 4 will not be destroyed by overvoltage. However, if the difference Δt between the extinguishing side of GTO thyristors 3 and 4 exceeds the failure value, the current in this current cutoff circuit will decrease. Before the time td when i becomes zero, the 7-node voltage V of the GTO thyristor 4 exceeds its withstand voltage, and the GTO thyristor 4 is destroyed by overvoltage. For example, in a GTO thyristor with a withstand voltage of 2.5 V and a controllable current of 1, the snubber capacitor capacity t required to suppress the rate of increase in anode voltage during extinguishing when the number of series connections is 1 is
is 2μF and 6D.The rate of increase in anode voltage from time t to tet of GTO thyristor 4, which is first extinguished at 9 o'clock when this GTO thyristor is applied to this current cutoff circuit to cut off lKN, is:

dvl ,,'a t = l (ni person"l/2 Cp
'F 1-500 (v/μs), so even if Δt = 1 (μB), E = 500 (V), which is a very difficult 1 shift for a GTO thyristor with a breakdown voltage of 2.5 Y. In addition, it is very difficult to make the difference Δt in the extinction time of the GTO thyristor, that is, the variation in the off time of the GTO thyristor, to less than lps at all junction temperatures used, so conventionally a snubber capacitor 12.13 dvt/ from time t to 1c1
GTO whose arc was decreased by dt2 and extinguished first by 2 at time td
The anode voltage v of the thyristor 4 is set to be less than its withstand voltage.

[Problem that the invention seeks to solve]

However, I like this! In a flow cutoff circuit, snubber 1; l! (2C6v 1 ” and g C8v2 ”) is G
During the period until the next firing of TO thyristors 3 and 4 and immediately thereafter, the snubber capacitor 12 and 13 are completely consumed by the snubber resistors 17 and 18 and the voltage of the snubber capacitor 12 and 13 becomes zero. Capacity C,'(
A problem arises in that an increase in r causes a proportional increase in the loss of this current cutoff circuit.

Therefore, the present invention prevents overvoltage breakdown of devices due to unbalanced voltage distribution caused by variations in turn-off time of self-extinguishing semiconductor devices connected in series.

The purpose is to provide a current cutoff circuit that prevents current loss with low loss.

[Means for solving problems]

The current cutoff circuit consists of a self-extinguishing semiconductor element connected in series, a diode, a capacitor, and a resistor, each connected in parallel with a snubber circuit that suppresses the rate of increase in surface pressure during arc extinguishing. A low voltage clamp circuit is connected in parallel to each element. By doing this, overvoltage breakdown of the element due to unbalanced voltage distribution caused by variations in element turn-off time can be prevented.
The snubber circuit for suppressing the rate of voltage rise when an element is turned off is intended to be prevented with low loss without causing a total increase.

[Practice of the Invention] FIG. 1 shows an implementation of the present invention, in which, in addition to the conventional example shown in FIG.
．． A voltage clamp circuit 1 consisting of a clamp power supply 29 and a clamp power supply 26 and 27 is connected in parallel to GTQ thyristors 3 and 4, respectively. FIG. 2 is a waveform diagram showing the operating waveforms of each part when the GTO thyristor 3.4 is turned off and the load current Ik is flowing from the state shown in FIG. is the same as in FIG. This diagram differs from Figure 5 in that the arc is turned on and the arc is extinguished first.
Since the anode voltage V of the thyristor 4 is at time t, the diode 29 is turned on and becomes the clamp power supply voltage E0 of the voltage clamp circuit, and this voltage E0 is lower than the withstand voltage of the GTO thyristor 3.4. Therefore, in the absence of this voltage clamp circuit, the GTO thyristor 4 whose anode voltage V is 7 can be prevented from being destroyed by overvoltage. In the embodiment shown in Fig. 1, the capacitance of the snubber capacitor 12.13 is GT.
This is the same as the snubber capacitor capacity of the snubber circuit for suppressing the voltage rise rate when the companion element is turned off, which is required when the number of O thyristors 3.4 is 1 in series.

Figure 3 shows another FJ' of the voltage clamp circuit shown by the dashed line in Figure 1, with a capacitor 30°31 and a resistor 3.
A clamp power supply is constructed by 2.33 parallel circuits. Here, the capacitance of the capacitor 30°31 is several times to 10 times the capacitance of the snubber capacitor 12°13 shown in Fig. 1, and the resistor 32°33 is set to the output characteristics (switching frequency, switching frequency, etc.) of the chopper circuit shown in Fig. 1. By appropriately selecting the on-width of the GTO thyristor, it is possible to create a clamp power supply with low overall loss in this parallel circuit.

〔Effect of the invention〕

According to the present invention, for a current cutoff circuit formed by connecting in parallel a snubber circuit for suppressing the voltage rise rate at the time of arc-extinguishing consisting of a diode and a capacitor/resistance to self-extinguishing semiconductor elements connected in series, Since the configuration is such that a voltage clamp circuit with a low withstand voltage is connected in parallel to each element,
This provides the advantage that overvoltage destruction of the device due to unbalanced voltage distribution caused by fluctuations in the turn-off time of the self-extinguishing semiconductor device that has been serially connected and turned off can be prevented with low loss.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram of each part for explaining its operation, and FIG. 3 is a circuit diagram showing another example of the voltage clamp circuit used in the present invention. Figure 4 is ii! Circuit diagram showing a conventional example of a current cutoff circuit, No. 5
The figure is the ninth waveform diagram of each part explaining the operation. Symbol explanation L...DC power supply, 2...DC bus wiring inductor 7s, 3-4...GTO thyristor, 5-6...freewheeling diode, 7...load resistance, 8...load inductance %9~11...Snubber diode,
12-16... Snubber capacitor, 17-21... Snubber resistor, 22-25... DC voltage dividing resistor, 26-27
...Clamp power supply, 28-29...diode. 30~31・Capacitor, 32~33・Resistor. Agent Patent Attorney Akio Namiki Agent Patent Attorney Kiyoshi Matsuzaki Figure 2

Claims (1)

[Claims] A snubber circuit comprising a diode, a capacitor, and a resistor for each of a plurality of self-extinguishing semiconductor elements connected in series between a DC power source and a load, and suppressing the rate of voltage increase when the element is extinguished. A high voltage current source or disconnection circuit formed by connecting in parallel a high voltage current source or disconnection circuit, characterized in that each of the elements is connected in parallel with a voltage clamp circuit having a clamp power source lower than the withstand voltage of the element. circuit.