JPS5983570A - Gate controller for gate auxiliary turn-off thyristor - Google Patents

Abstract

PURPOSE:To eliminate wasteful time by driving an OFF gate signal generator by the output of a comparator for detecting the fact that a current flowed to a thyristor has passed substantially zero point from positive to negative. CONSTITUTION:A current flowed to a thyristor 1 is always detected by a current transformer 11, and compared by a comparator of a gate controller 12 with a set value. When a current flowed to a thyristor is vibrated so that the vibrating current becomes smaller than the set value, the comparator generates a drive signal, thereby reversely biasing the thyristor 1. This OFF gate signal is applied between the gate and the cathode of the thyristor 1 until the vibrating current becomes larger than the set value at the time immediately before the finish of the initial half cycle of the vibrating current.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a gate-assisted turn-off thyristor (hereinafter referred to as
This invention relates to a gate control device for a thyristor (abbreviated as GATT).

FIG. 1 is a circuit diagram of a series arc-extinguishing type repulsion pulse type chopper circuit constructed using GATT.

In the figure, 1 is the thyristor GATT, 2 is the saturable
Reactor, R and L are resistance and inductance of load 3, 4 is flywheel diode, 5 is commutating auxiliary thyristor, 6 is commutating capacitor, T is thyristor GAT
T1 gate signal generator, 8 commutation auxiliary thyristor 50
The on-gate signal generator 9 is a direct current power source for the voltage Ed.

Figure 2 shows the thyristor GAT in the above chopper circuit.
On-gate signal G0 and off-gate signal Gp of TI On-gate signal g of commutating auxiliary thyristor 5 1 Current flowing through thyristor GATT 1 n 1 Capacitor current lc of commutating capacitor 6 and Q% The waveform of capacitor voltage VC is shown. .

On-gate signal g of commutation auxiliary thyristor 5. The time width t of n is generally the capacitor current l. the first positive half rhino,
This is set to a time width that is wider than the cycle time (3/4) and smaller than the cycle time.
A. This is because the point in time when the photographing current flowing through TT1 becomes zero is between the half cycle and 3/4 cycle. The above-mentioned time width tW is actually the current i when the DC voltage is the minimum and the load current is the maximum, taking into account fluctuations in the DC' voltage Ed and load. The off-gate signal GFn is determined based on the point in time when the on-gate signal g passes the zero point, and the off-gate signal GFn is generated by the fall of the on-gate signal g.

Therefore, as shown in Figure 3, when the power supply voltage Ed is the minimum and the load current is maximum, the current l (indicated by the broken line) passes through the zero point To, when the power supply voltage Ed is at its maximum and the load current is at its minimum. The point at which the current l (shown by the solid line) passes the zero point is T
, and there is a problem that there is a dead time ΔT until the off-gate signal GF is generated.

This invention was made in view of the above-mentioned problems.
By configuring the off-gate signal generator to be driven by the output of the comparator that detects that the current flowing through the thyristor GATT changes from positive to negative and passes through the zero point,
It is an object of the present invention to provide a gate control device for a gate auxiliary turn-off thyristor that can eliminate the above-mentioned dead time.

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

In FIG. 4, the same parts as in FIG. 1 are given the same reference numerals. 11 is a current transformer, which is a thyristor GAT.
Amount of current flowing through T1. Detect.

The detection signal of the current transformer 11 and the gate signal g sent out by the gate signal generator 8 are supplied to the gate control device 12 of the thyristor GATTn 1.

This gate control device [12] will be described in detail with reference to FIG. In the figure, 121 is a one-shot multivibrator, and gate signal generator B outputs an on-gate signal g.
. n is guided, and a pulse number 1M-P of width is sent out for a predetermined period of time. 122 is a comparator, from which the detection signal (referred to as i for convenience of explanation) output from the current transformer 11 is guided;
When the level falls below a negative set value - close to zero, the drive signal P is activated.

Send out. 123 is an AND element to which a pulse signal P and a drive signal P are supplied, and its output P drives an off-gate signal generator 124 constituted by a one-shot multivibrator. The off-gate signal G output from the off-gate signal generator 124 is supplied between the gate and cathode of the FF°C thyristor GATT1 through a signal combiner 125. 126 is thyristor GATT 10 on gate 4
The on-gate signal G that is sent out by the δ generator
is supplied through the signal combiner 125 to the gate of the sign n risk GATT1.

It should be noted that the time width Tw of the pulse signal P sent out by the Wanzoyacht multi-pisolator 121 is the same as that of the capacitor when the power supply voltage Ed is minimum and the load current is large. It has a magnitude corresponding to approximately 4 u per cycle time of current.

Next, the operation of the device C will be explained with reference to the waveform time chart of FIG.

Amount of current flowing through thyristor GATT'1. is always '
atrffi transformer 11 and compared with a set value - in comparator 122. After the on-gate signal G is supplied to the gate of the thyristor GATT1 at time t6 and the thyristor GATTI becomes conductive, at the time t, the on-gate signal G is input to the gate of the commutation auxiliary thyristor 5, which connects the n capacitor through the commutation circuit. [The current lc flows and the current IGfJ'--starts to flow through the thyristor GATT1. This imaging current exceeds the zero level to the negative side at time t, and at time t.

When the set value becomes smaller than -, the comparator 122 outputs the drive signal P! occurs. At this time, since the pulse signal P, has already been sent out from the one-shot multivibrator 12'1, the liA signal P, is supplied to the off-gate signal generator 124 through the AND element 123, and the thyristor G
Off gate signal G between gate and cathode of ATTI
is added, and the FF risk G AT T 1 is reverse biased. This off-gate signal G. FF is the oscillating current l. at time t, just before the end of the first negative half cycle of .

)- between the gate and cathode of thyristor GATT1.

As described above, according to the present invention, the current flowing through the thyristor GATT is constantly monitored, and after the start of commutation, the off-gate signal generator is driven after the first half cycle of the oscillating current has elapsed. By providing this, reverse bias can be applied to the thyristor GATT immediately after the current passes through the zero point, regardless of load fluctuations, power supply voltage fluctuations, or the presence or absence of a saturable reactor. This eliminates the above-mentioned wasted time and reduces the turn-off time. Can be shortened.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a chopper device using a gate-assisted turn-off thyristor, FIGS. 2 and 3 are waveform time charts, and FIG. 4 is a block diagram showing an embodiment of a gate control device for a gate-assisted turn-off thyristor according to the present invention. figure,
FIG. 5 is a concrete block diagram of the above embodiment, and FIG. 6 is a time chart of waveforms of various parts in the above embodiment. In the figure, 8...On-gate signal generator, IL...Current transformer 1
21...One-shot multi-pifrator 122...
Comparator, 123...AND element, 124...Off gate signal generator 126...On gate signal generator. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Agent Shin Kuzuno −

Claims (1)

[Claims] comprising a comparator, an off-gate signal generator, and an off-gate signal generator that derives a signal corresponding to the current flowing through the gate-assisted turn-off thyristor and outputs the signal when the signal is less than or equal to a negative set value, and the off-gate signal generator is configured as described above. A gate control device for a gate-assisted turn-off thyristor, characterized in that it is driven by the output of a comparator.