JPH0382150A - Snubber circuit - Google Patents

Abstract

PURPOSE:To reduce the induction of a snubber circuit for protecting a GTO element by a method wherein the diode and the capacitor of the snubber circuit are formed into a flat type form joinable by pressure welding and are joined to each other by pressure-welding between heat sinks, which are respectively pressure welded to a self-arc-extinction thyristor, through a striplike conductor. CONSTITUTION:A diode 4 of a flat type form is arranged to a heat sink 7A on the side of the anode of a GTO element 1, a capacitor 5 of a flat type form is arranged to a heat sink 7K on the side of the cathode of the element 1, the diode 4 and the capacitor 5 are pressure-welded and pressed by clamping devices 10, which are respectively provided with a conical spring 10a, a clamping bolt 10b, a case 10c and the like, through a striplike conductor 8, which connects electrically the diode 4 with the capacitor 5, and a snubber circuit is constituted. The capacitor 5 is formed in a structure wherein the case itself can withstand sufficiently a pressure-welding load for connecting electrically. Moreover, it is also possible that the capacitor 5 is constituted of a conductive metal constituting the case itself which is used as one terminal in combination, such as copper, brass and the like. That is, the snubber circuit is constituted at the shortest distance from the element 1 without using electric wires and the inductance of the circuit is reduced as much as possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a snubber circuit consisting of a series circuit of a diode and a capacitor connected between the anode and cathode of a self-extinguishing thyristor.

(Prior Art) A snubber circuit is an important protection circuit for suppressing overvoltage applied when a self-extinguishing thyristor is turned off.

Snubber circuits can generally suppress the overvoltage applied to self-extinguishing thyristors by increasing the capacitance of the capacitor, but unnecessary increases increase the power loss consumed by the resistor, so the snubber circuit It is desirable to minimize the stray inductance of the snubber capacitor and suppress overvoltage without increasing the capacitance of the snubber capacitor.

In this sense, it is very important to reduce inductance by keeping the wiring between the diode, capacitor, and self-extinguishing thyristor as short as possible.

Figure 6 shows a general self-extinguishing thyristor (hereinafter referred to as GTO).
A gate circuit 2 that supplies an on/off signal to a GTO element 1 is connected to the circuit. A snubber circuit 3, which is a protection circuit for the GTO element 1, is connected in parallel to the GT○ element 1. The snubber circuit 3 includes a diode 4, a capacitor 5, and a resistor 6.

The capacitor 5 absorbs overvoltages such as surges, suppresses the off-voltage increase rate dv/dt, and reduces the overvoltage applied to the GTO element 1. The diode 4 has a resistor 6, forms a bypass circuit, allows current to flow through the capacitor 5, and also has a reverse blocking effect so that the GTO element current does not flow directly when the capacitor 5 is discharged.

The resistor 6 discharges the energy of the capacitor 5 that has absorbed overvoltage such as a surge, and also suppresses the rise of the current so that it does not flow suddenly.

Overvoltage and off-voltage increase rate dν/d of conventional GT○ element 1
As shown in FIG. 7, the snubber circuit shown in FIG. 6 for suppressing t is implemented by installing a diode 4. in the vicinity of the heat sinks 7A and 7 disposed on the anode and cathode surfaces that press the GTO element 1. Installing capacitor 5 is diode 4 and capacitor 5.
and the heat sinks 7A, 7 are connected to each other by an electric wire 9 (6) (This is a problem to be solved by the invention!) A diode 4 and a capacitor 5 having such a configuration are arranged near the heat sinks 7A, 7. However, the wiring inductance between the GTO element element type node and the cathode increases, and an overvoltage exceeding the allowable withstand voltage value of GT○ element 1 is applied, which may cause the GTO element element type to break. In some cases, it may not be possible to take full advantage of the characteristics of

SUMMARY OF THE INVENTION An object of the present invention is to provide a snubber circuit which is connected in parallel to a GTO element and can fully demonstrate its performance by reducing the inductance of the snubber circuit that protects the GTO element.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention has a snubber circuit diode and a capacitor in a flat shape that can be pressure-bonded, and a strip-shaped conductor is provided between a heat sink that pressure-bonds a self-extinguishing thyristor. This feature is characterized by a configuration in which pressure welding is carried out through the contact.

(Function) As mentioned above, by making the diodes and capacitors of the snubber circuit into a flat shape that can be pressure-connected, the diodes and capacitors can be pressure-connected between the heat sinks via a strip conductor, and the shortest distance can be achieved without using electric wires. By configuring a snubber circuit at a distance, it was possible to reduce circuit inductance as much as possible.

(Embodiment) Hereinafter, an embodiment of the present invention using a GT○ element will be described with reference to FIG. The connection configuration of the snubber circuit is the same as that shown in FIG. Figure 1 shows a stack configuration diagram, and the GT○ element 1 is fastened to the heat sink 7A, 7 that cools the GTO element 1! ! (not shown) is pressed and held to form a stack.

A flat diode 4 is placed on the heat sink 7A on the anode side of the GTO element 1, and a flat capacitor 5 is placed on the cathode side heat sink 7K. , the capacitor 5 has a disc spring 10a and a tightening bolt 1, respectively.
0b, case 10c, and other components are pressurized by device 10 to form a snubber circuit.

The capacitor 5 has a structure that allows the case itself to sufficiently withstand the pressure contact load for electrical connection. It is also possible for the mata case itself to be made of a conductive metal, such as copper or brass, which also serves as one terminal.

FIG. 2 shows another first embodiment of the present invention, in which the capacitor 5 has a flat structure that can be pressure-bonded as described above, and its two terminals are located at right angles and are bonded to the heat sink 7K on the cathode side of the GTO element 1. The terminals to be tightened are the same as in Figure 1 using device 10.
The snubber circuit is connected by a bolt or nut, and the other terminal connected to the strip conductor 8a has a female screw or stud.

FIG. 3 shows a second embodiment of the invention, in which the diode 4
A snubber circuit is constructed by pressure-welding a terminal 11 for wiring to a capacitor 5 and a resistor 6, and a strip conductor 8b in FIG. Note that the strip-shaped conductor 8 shown in FIGS. 1 to 3 may be a flexible conductor.

FIG. 4 shows a stacked structure in which the aforementioned capacitor 5, diode 4, and terminal 11 for wiring to the resistor 6 are tightened at a predetermined pressure using a device (not shown), and the mounting leg 12 is connected to the terminal. It also serves as a snubber circuit and is connected to heat sinks 7A and 7K with bolts.

FIG. 6 shows still another embodiment of the present invention, in which the conductor connecting between the diode 4 and the capacitor 5 is connected to the diode 4 and the capacitor 5.
This is an example in which a capacitor 5 is provided with fins to radiate heat generated from the capacitor 5. In addition, the strip conductors 8.8a and 8b in FIGS. 2 to 4
, it is also possible to use the terminal 11 as a radiation fin.

〔Effect of the invention〕

As explained above, according to the present invention, the connection path between the diode and the capacitor connected in parallel to the GTO element is the shortest possible, and the connection between them can be made with a strip conductor without connecting with an electric wire. The area and surface area are increased, the inductance can be minimized, and the heat dissipation effect can also be improved. Additionally, the contact area of the capacitor's terminals increases, making it possible to reduce the inductance of the capacitor itself.

Therefore, the inductance of the snubber circuit can be minimized, and the G
The performance of the TO element can be fully demonstrated.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIGS. 2 to 5 are block diagrams showing different embodiments of the present invention, and FIG.
The figure is a connection configuration diagram of a snubber circuit, and FIG. 7 is a configuration diagram of a conventional snubber circuit. 1... Self-extinguishing thyristor 2... Gate circuit 3... Snubber circuit 4... Diode 5... Capacitor 6... Resistor 7A,
7K...Heat sink 8...Strip conductor 9
...Wire IO...Tighten with device 10a...Disc spring 10b...Tighten with bolt 10c...Case 11...
・Terminal 12...Mounting leg

Claims (1)

[Claims] In a snubber circuit consisting of a series circuit of a diode and a capacitor connected between an anode and a cathode of a self-arc-extinguishing thyristor, the snubber circuit is provided on an anode side and a cathode side of the self-arc-extinguishing thyristor, respectively, and the self-arc-extinguishing thyristor is 1. A snubber circuit characterized in that a heat sink to be pressed into contact with the diode and the capacitor have a flat shape that can be connected to each other by pressure contact, and the heat sinks are connected to each other by pressure contact via a strip-shaped conductor.