JPS60219916A - Element defect detecting circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a gate turn-off thyristor (hereinafter referred to as a GTO).
The present invention relates to a circuit for detecting an abnormality in an element (abbreviated as ), and particularly relates to an element failure detection circuit for detecting an overcurrent of a gate power supply to detect a short-circuit failure of an element.

[Technical background of the invention and its problems]

Conventionally, short-circuit failures in GTOs have been discovered by detecting overcurrent in the main circuit due to DC shorts or arm shorts on the device side, or by stopping the device and conducting device checks, gate checks, etc. However, when multiple GTOs are used in series,
In some GTQ failures, a short circuit in the main circuit prevents the magnetic current from flowing, and it cannot be discovered until one element is checked when the equipment is stopped during periodic inspections, etc., and overvoltage may occur due to the intrusion of surge voltage from the outside. At times, the original design margin could not be secured, and there was a risk that failure of some GTO elements could damage other healthy elements, leading to serious accidents. Therefore, conventionally, the circuit shown in FIG. 1 has been used to detect failures in GTOs connected in series. In the figure, 11~
16 is a GTO, and here the case of 6 series connections is shown. 17 and 18 are voltage dividing resistors, and 19 is a current detector. When all GTOs 011 to 16 are normal, the 0 point and the D point are at the same potential, and no current flows between C and 0. However, when the GTO has a short-circuit failure, the current flows between C and D. A current flows through the element, and this current is detected by a current detector 19 to detect an element abnormality. The fault detection method described above is the upper half (
Since element failure is detected based on the voltage difference between the voltage difference between the voltage between It has the disadvantage that it cannot be detected. Furthermore, as the number of GTOs connected in series increases, a resistor with a high withstand voltage is required, and the variation in GTO turn-off is different between the set of GT011-13 and the set of GT014-16.
If there is a difference between the sets, there will be a difference in the DC voltage applied to each element, and even if the elements are normal, a potential difference will occur between the 0 point and the D point, which may lead to entertainment detection.

[Purpose of the invention]

An object of the present invention is to be able to detect a failure in a GTO using a gate power supply circuit without providing a detection circuit in the main circuit. 9
An object of the present invention is to provide a T O element failure detection circuit.

Summary of the Invention] In order to achieve this object, the present invention detects the current of a gate power supply circuit that supplies current to a pulse transformer, and detects an element failure when the current becomes an overcurrent. This is what I did.

[Embodiments of the invention]

FIG. 2 is a configuration diagram showing an embodiment of the present invention. G
TOIQ is turned off by an off-gate current supplied via a pulse transformer 26. 1 full winding wire N of pulse transformer 26! is connected to one end of a capacitor 45 that stores charge for supplying a large off-gate current with a fast rise, and when the transistor 44 is turned on, a discharge current is generated. An AC power supply 80 passes through an isolation transformer 60 and is converted to DC by a rectifier 50.
After smoothing with a DC filter circuit consisting of a resistor 47 and a capacitor 46, the current is passed through the primary winding N of the pulse transformer 26 via a current detector 48 that detects overcurrent when an element is abnormal, and a diode 43.
, connected to one end of the . The current detected by the current detector 48 is converted into a voltage signal 31, and the current detected by the current level detector 3
Enter 21 items. Current level detector 32 detects voltage signal 31
It detects that the level has exceeded a certain level, and outputs a GTO failure signal 33.

Next, the operation of the present invention will be explained with reference to FIGS. 2 and 3. FIG. M3 is a diagram showing waveforms of various parts of the present invention, which is not explained in detail. (a) is the waveform of the voltage VC of the capacitor 45, (b) is the gate-cathode voltage waveform of GTOIQ, vQ-K, (C) is the off-gate current I2, (d
) shows the waveform of the input current I of the pulse transformer 26. In FIG. 3, from time t0 to 1zt,
A base signal is supplied to the transistor 44 in FIG.
It's turned on. When the GTO element 10 is normal,
The dashed line indicates when GTolo is cutting off the current, GTO
The solid line indicates the case where only one off-gate current is supplied during no-load when no current flows to the IO. GT
Comparing when Olo is cutting off the current and when there is no load, the timing at which the reverse voltage (approximately 20V) is generated on VO- in (b) is delayed by 5 to 10 μs when the current is cut off.

In addition, the off-gate current (2) in (C) is different from that at no load when the current is cut off (1).Since the impedance between the gate and cathode of GTOlo is low, the shaded part continues to supply the charge necessary for turn-off of GT OIQ. It increases by the amount of charge of ■ and ■. On the other hand, the primary winding N of the pulse transformer 26
The input current island to , has the waveform shown in (d). next,
Considering the overcurrent 1 in case GTOlo is short-circuited between the gate and cathode due to element failure, the excitation inductance L of the pulse transformer is generally considered. is the leakage inductance/
. It is several ten times larger than . If the element is normal,
JR is the voltage-time product applied to the primary winding of the pulse transformer 260. Since the current increases to the value divided by , the current becomes IRI at time t.After that, when the transistor 44 is turned off, the excitation energy stored in the primary winding N of the pulse transformer 26 is transferred to the N1 winding. Therefore, it increases to about twice the engineering R1. On the other hand, in the event of a short-circuit failure of the element, I,
What suppresses the increase in is the number 1 of the excitation inductance L0.
Leakage inductance e is about 1/0. , and continues to increase while the transistor material is turned on. Therefore, assuming that the smoothing capacitor 46 of the DC power supply is sufficiently large, a current several ten times the normal IR1 flows from the capacitor 46. Therefore, if the current detector 48 detects a short-circuit fault current that is several tens of times larger than the normal capacitor discharge current, a short-circuit fault of the GTO can be detected.

FIG. 4 shows another embodiment of the invention.

Components that are the same as those in FIG. 2 are given the same reference numerals, and their explanations will be omitted. Instead of the overcurrent detection 4 shown in FIG. 2, a current transformer 48A may be used to detect the charging and discharging current of the capacitor 46, as shown in FIG.

Figure 5 shows the capacitor 6 to the gate circuits 70 to 723.
6 shows another embodiment of the present invention configured to collectively detect charging and discharging flows from 6 to 6.

FIG. 6 shows another embodiment of the present invention in which one current transformer 48A is used to detect the input current of the gate power supply in the configuration shown in FIG.

〔Effect of the invention〕

As described above, according to the present invention, by detecting an overcurrent of the gate power supply and detecting a short-circuit failure of an element, abnormalities in individual GTOs configured by connecting multiple GTOs in series can be detected. , it is possible to provide an element failure detection circuit that is highly effective in preventing serious accidents such as damage to other healthy elements and protecting the device.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional element failure detection circuit, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a waveform diagram of each part for explaining the operation of FIG. FIGS. 4 to 6 are configuration diagrams showing other different embodiments of the present invention. 10-16...GTOi child 26...Pulse transformer 32...Level detector 44...Transistor 45
... Capacitor 46 ... Smoothing capacitor 48
... Overcurrent detector 50 ... Rectifier 48A ... Current transformer 80 ... AC power supply (7317) Representative patent attorney
Kensuke Chika (and 1 other person) Figure 11 Figure 2 Figure 32 Figure 3 Figure 4

Claims (2)

[Claims] (1) Two windings N, N! on the primary side! , connect a diode to one end of the N winding with the polarity where current flows from the positive electrode of the DC power supply, connect the other end of the N1 winding to one end of the N3 winding and one end of the capacitor, and connect the N2 winding to one end of the N3 winding and one end of the capacitor. The other end of the wire is connected to the other end of the capacitor and the negative electrode of the DC power source via a switching element, and the electrical charge of the capacitor is discharged via the N2 winding by turning on the switching element. In a gate circuit of a gate turn-off thyristor having a pulse transformer that supplies an off-current to the gate of the gate turn-off thyristor via a secondary winding N, an overcurrent detector detects an overcurrent flowing through the N1 winding. An element failure detection circuit comprising: an element failure detection circuit having a characteristic of detecting an element failure using the output of the detector. (2) The overcurrent detector detects a current of a smoothing capacitor forming the DC power supply, a current of a smoothing capacitor forming the DC power supply, or an input current of a rectifier forming the DC power supply. 17. The element failure detection circuit according to claim 1, characterized in that: