JPS6345008Y2 - - Google Patents

Description

[Detailed explanation of the idea] This invention relates to a protection device for GTO elements.

As is well known, when a GTO element is turned off by a gate signal, means are taken to bypass the anode current. In this case, the voltage rise rate
If dv/dt is large, the cut-off withstand capability of the GTO element decreases, so a snubber circuit, which will be described later, is used. 1st
The figure is an electrical circuit diagram of a GTO element equipped with a snubber circuit. In this figure 1, 1 is the GTO element,
A series circuit of a discharge resistor 2 and a capacitor 3 is connected between the anode and cathode of this element 1, and a diode 4 of the polarity shown is connected in parallel with the resistor 2. In FIG. 1, a circuit consisting of a discharge resistor 2, a capacitor 3, and a diode 4 is a snubber circuit 5. In this way, when connecting the snubber circuit 5 to the GTO element 1, a predetermined lead wire is used. For example, in FIG. 1, when connecting the anode of GTO element 1 → diode 4 → capacitor 3 → cathode of GTO element 1 using lead wires 6a and 6b, if the inductance L of the lead wires 6a and 6b is large, this Due to L and the anode current attenuation rate di/dt of the GTO element 1, an overvoltage _VSI as shown by the dotted line in FIG. 2 is generated across the GTO element 1. Since the di/dt is usually as high as 1000 A/μs, the minute inductance caused by the lead wires 6a and 6b becomes a problem.

Here, a specific configuration of the circuit shown in FIG. 1 is shown in FIG. 3. In FIG. 3, the GTO element 1 is formed into a flat shape, and the element 1 has cooling fins 7.
a and 7b, and is tightened to a predetermined pressure by a tightening clamp 8. The lead wire 6a,
When connecting 6b to the anode and cathode sides of GTO element 1, cooling fins 7a and 7 are used for ease of wiring work.
It is connected to the end face of b as shown. Note that the lead wires 6a and 6b are usually insulated flat parallel conductors, ribbon parallel cables, or hot wires so as to minimize the wiring inductance L. However, the bypass current flowing through the snubber circuit 5 is caused by cooling fins 7a and 7b as shown by arrows in FIG.
flows through the inner world. This current flows through the cooling fin 7
a, 7b and the lead wires 6a, 6b connected to the end faces of the GTO element 1 and the cooling fin. This caused a decrease in the cut-off withstand capability of the GTO element.

The object of this invention is to provide a protection device for a GTO element that eliminates the above-mentioned drawbacks, suppresses the spike voltage when the GTO element is turned off, and improves the cut-off withstand capability of the GTO element.

An embodiment of this invention will be described below with reference to the drawings, in which the same parts as in FIGS. 1 and 3 are denoted by the same reference numerals. In FIGS. 4A and 4B, reference numeral 10 denotes an auxiliary conductor made of a conductive plate formed into a U-shape, and this auxiliary conductor 10 is formed into an inverted U-shape inside the space 9 as shown in FIG. 4A. will be arranged. One end of the auxiliary conductor 10 connects the GTO element 1 with cooling fins 7a,
Before being clamped between the cooling fins 7b, it is fixed in advance to the element mounting surface of the cooling fin 7b. The other end of the conductor 10 is screwed together with the lead wire 6b to the end surface of the cooling fin 7b with a screw 11. One surface portion 10a of the auxiliary conductor 10 is disposed close to and facing the bottom surface portion of the cooling fin 7a, so that an insulating coating is formed to prevent short-circuiting even if the surface portion 10a comes into contact with the bottom surface portion. In addition, in the case of a bare conductor that does not have an insulating coating, the gap with the bottom surface of the GTO element 1
Ensure that the space distance is sufficient to withstand the voltage applied to both ends of the

Normally, the distance between cooling fins 7a and 7b is GTO
AC is equal to the thickness of element 1 (15 to 20 mm)
When used at 400V, it is preferable to coat the auxiliary conductor 10 with an insulating coating.

When the auxiliary conductor 10 is disposed in the space 9 as described above, the volume of the space becomes the space area shown in the mesh shape in FIG. 4A. The area of this space is approximately 1/8 of the area of the space 9 in FIG. 3.
Note that the inductance at this time is reduced to about 1/3 compared to the conventional one. This was confirmed by experiment. Therefore, the spike voltage at turn-off of the GTO element 1 was significantly reduced, and the cut-off withstand capability of the GTO element was improved by 20%.

Figure 5 shows another embodiment of this invention.
The same parts as in FIGS. 4A and 4B are designated by the same reference numerals. FIG. 5 shows an embodiment in which the cooling fins 7a and 7b have different shapes. In this embodiment, the first and second auxiliary conductors 13 and 14, which are formed in a U-shape between the fin portions 12a and 12b, are placed close to each other. This is what was placed. In this way, the first and second auxiliary conductors 13, 1
By reducing the volume of the space between the fin portions 12a and 12b in step 4, the inductance can be greatly reduced, so that the same effect as described above can be obtained.

As described above, according to this invention, the auxiliary conductor is provided to significantly reduce the volume in the closed loop caused by the bypass current of the snubber circuit formed by the cooling fin, the lead wire of the snubber circuit, and the GTO element. There are various advantages such as being able to suppress an increase in inductance due to a closed loop, significantly suppressing the spike voltage at turn-off of the GTO element, and improving the cut-off withstand capability of the GTO element.

[Brief explanation of drawings]

Fig. 1 is an electrical circuit diagram of a GTO equipped with a snubber circuit, Fig. 2 is an anode current and voltage characteristic curve diagram at turn-off of the GTO element, Fig. 3 is an explanatory diagram of a conventional concrete configuration, and Fig. 4 is an electrical circuit diagram of a GTO equipped with a snubber circuit. Figures A and B show one embodiment of this invention. Figure 4A is a front view, Figure 4B is a plan view, and Figure 5 is a front view of main parts showing another embodiment of this invention. It is. 1... GTO element, 5... Snubber circuit, 6a,
6b... Lead wire, 7a, 7b... Cooling fin,
10...Auxiliary conductor.

Claims (1)

[Scope of utility model registration request] The cathode and anode of the flat GTO element are clamped and pressure-welded with cooling fins, and a snubber circuit consisting of a capacitor, diode, and resistor for suppressing dv/dt when the GTO element turns off is led to the ends of the pair of cooling fins. In a GTO device that is grounded separately by a wire, one of the cooling fins is connected to a cooling fin portion to which the lead wire is connected, a cooling fin portion to which the GTO element is clamped, and a space region formed by a pair of cooling fins. A protection device for a GTO element, characterized in that an auxiliary conductor having the same DC potential as a cooling fin is disposed close to the other cooling fin.