JPS63100817A - Snubber circuit for gate turn-off thyristor - Google Patents

Abstract

PURPOSE:To balance currents flowing to GTOs at turn-off by using two gate turn-off thyristors GTOs in pairs and arranging a turn-off snubber circuit at the middle of both GTOs. CONSTITUTION:The titled circuit consists of two GTO modules connected in parallel. Anodes and cathodes of the GTO modules are connected by copper bus bars 2a, 2b and the snubber circuit, especially a snubber diode 4 and a snubber capacitor 5 in the turn-off snubber circuit are provided between the bus bars 2a and 2b so as to be placed summetrically (inbetween both modules) with respect to a line segment A-A. Thus, the wiring impedance of the snubber circuit is equal, and the currents iS1, iS2 flowing from both GTOs to the snubber circuit through commutation are balanced, then anode currents iA1, iA2 are also balanced and the locus comprising the anode current iA and the anode-cathode voltage VAK is kept.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a snubber circuit for a gate turn-off thyristor (hereinafter abbreviated as GTO), and in particular, when two GTOs are directly connected in parallel and operated, the snubber circuit is The present invention relates to a snubber circuit suitable for simplifying the snubber circuit and improving turn-off operation.

[Conventional technology]

A layout diagram of a snubber circuit when two conventional GTOs are directly connected in parallel is shown in FIG. 3, and a circuit diagram is shown in FIG. 4.

FIG. 3 shows a configuration for one inverter arm, in which a snubber circuit is attached to each GTO module 1. The snubber circuit is a polar snubber circuit with three snubber resistors.
．． It consists of a snubber diode and a 4° snubber capacitor 5. Snubber resistor 3, snubber capacitor 5 is for turn-on, snubber diode 4. Snubber capacitor 5 constitutes a turn-off snubber circuit.

In FIG. 3, 2a and 2b are bus bars for the anode and cathode.

This kind of thing is Ivy Easy Tokyo March 27-31.1983. Volume 1 International Power Electronics (IPEC-Tok
yo March 27-31.1983 Vofl
,! INTERNATIONAL POWERELEC
TRONIC3), pages 54 to 64.

[Problem that the invention seeks to solve]

With the snubber circuit wiring and position when the conventional GTOs are directly connected in parallel, an imbalance of wiring impedance occurs in each snubber circuit. Also, each snubber diode 4.
Since the internal impedance of the snubber capacitor 5 differs, when the GTO is turned off, the anode current i^1. The snubber current is commutated to the snubber circuit during the falling period of i^2, isx
varies.

That is, L (isz side) X d ist/d t =
Since L (isz side) Xdisz/dt=constant,
1, dis/dt varied, and the snubber currents xsi and xsz also varied. Therefore, iAl.

i^2 will vary during the falling period, and iAl and ■
There was a problem that the locus of ^ swelled outward from the locus of i^2 and vAK, leading to destruction outside the ASO (safe operating area) or element deterioration.

It is an object of the present invention to eliminate the above-mentioned problems and to provide a GT
The purpose is to provide an O snubber circuit.

[Means for solving problems]

In order to solve the above-mentioned problem, one method is to accurately align the snubber circuit wiring impedance and the internal impedance of the snubber diode 7° and snubber capacitor 9, but it takes time to align and select passive elements. It has the disadvantage of being wasted.

Therefore, the above purpose is to unify the snubber circuit, and in particular to place the off-snubber circuit (path of the snubber diode and snubber capacitor) in a symmetrical position, that is, in the middle, with respect to the GTOL, which has two directly connected in parallel. resolved.

[Effect]

In the wiring shown in Fig. 3, the current waveform is as shown in Fig. 5, so the snubber circuit is single and shared for one GTO, and if it is placed in a symmetrical position, the impedance that occurs when the two snubber circuits are Misalignment of the off-snubber circuit can be eliminated. Therefore, during the GT○ drop period, the current imbalance of the snubber currents i sz and i sz commutated to the snubber circuit can be reduced, the operation near AS○ can be suppressed, and the GT
Deterioration or destruction of O can be prevented.

On the other hand, in the turn-on snubber circuit, in order to suppress the anode current increase rate di/dt at GTO turn-on, the wiring of the snubber resistor is usually made long (di/dt is loose, and the turn-on current is not so unbalanced). )
The turn-off snubber circuit does not need to be placed at a symmetrical position with respect to both GTOs, that is, in the middle between both GTOs.

[Practical example]

An embodiment of the present invention will be described below with reference to FIG. FIG. 2 is an equivalent circuit of FIG. 1.

FIG. 1 shows two GTO modules directly connected in parallel. The GTO module 1 includes copper busbars 2a, 2
b connects the anode and cathode of each module, and the snubber diode 4 and snubber capacitor 5 of the snubber circuit, especially the turn-off snubber circuit, are connected by the line segment A −
It is provided between the bus bars 2a and 2b so as to be placed at a symmetrical position with respect to A (center of both modules).

Therefore, the wiring impedance in the snubber circuit becomes equal, and the currents isx and isz commutated from both GTOs to the snubber circuit are balanced.Therefore, the anode currents iAz and 'hAx are also balanced, and the difference between i^ and V^ is Can't leave the locus.

When an even number of GTOs are connected in parallel, a snubber circuit is placed at the center of each GTO unit, with two GTOs as a unit.

Although the flywheel diode is not mentioned in Figures 1 and 2, the flywheel diode may be connected in antiparallel to each GTO, since no current flows through the flywheel diode at turn-off. The snubber circuit can be placed in any position relative to the flywheel diode; conversely, the snubber circuit can be placed in any position relative to the flywheel diode.
When sealed with the TO, care should be taken to position the GTO so that the snubber circuit is centered, and the flywheel diode can be mounted anywhere within the package.

〔Effect of the invention〕

According to the present invention, when manufacturing a device such as an inverter by directly connecting two GTO modules in parallel, the turn-off snubber circuit (pass between the snubber diode and the snubber capacitor) is unified, and the symmetrical connection of both GTO modules is performed. position, that is, in the middle, to ensure GT
It is possible to suppress the current imbalance during the drop period at O turn-off, prevent switching operation near the ASO region, and make the device more compact by integrating the snubber circuit.

Furthermore, this method can also be applied when two earring elements are directly connected in parallel in a case where a polar snubber circuit is desired.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of a GTO showing one embodiment of the present invention;
The figure is an equivalent circuit diagram of Figure 1, Figure 3 is a perspective view of a GTO showing an example of conventional direct parallel connection, Figure 4 is an equivalent circuit diagram of Figure 3, and Figures 5 (a) to (c). is a diagram showing voltage and current waveforms (at turn-off) at each point in FIG. 3. 1...GTO module, 2...copper busbar, 3.
...Snubber resistor, 4...Snubber diode, 5...
Snubber capacitor, 6... GTO17... Snubber diode, 8... Snubber resistor, 9... Snubber capacitor.

Claims (1)

[Claims] 1. In a device in which gate turn-off thyristors are connected in parallel, two gate turn-off thyristors are set as one set, and one turn-off snubber circuit is arranged in the center of both gate turn-off thyristors. Features a gate turn-off thyristor snubber circuit. 2. The snubber circuit for a gate turn-off thyristor according to claim 1, wherein the snubber circuit is connected to a bus bar connecting two gate turn-off thyristors in parallel.