JPH05276654A - Protective method for semiconductor element - Google Patents

Abstract

PURPOSE:To provide a protective method for semiconductor element through which downsizing of protective unit and reduction of manufacturing cost can be realized by reducing the number of semiconductor elements, connected in series and reverse series, in a power semiconductor device. CONSTITUTION:Ground arresters 4, 5 are connected, respectively, to the input side and the output side of a semiconductor device for power system unit in which arresters 3 between A-K are connected in parallel with semiconductor elements 1. Upon intrusion of a lightning surge current into the semiconductor device, majority thereof is fed through the ground arrester 4 or 5 to the ground in order to suppress current flowing into the A-K arrester 3 thus lowering the limit voltage of the A-K arrester 3 below the rated voltage of the semiconductor element 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor element protection method for protecting a semiconductor element such as a thyristor used in a power system device from a lightning surge.

[0002]

2. Description of the Related Art As shown in FIG. 2, when a semiconductor device 1 such as a thyristor is used as a switching device of a power system by connecting it in a reverse series, a snubber circuit 2 is arranged in parallel with each semiconductor device 1. It is usual to make the shared voltage of each semiconductor element 1 uniform and to mount the AK arrester 3 made of ZnO element in parallel with the semiconductor element 1.

The A-K arrester 3 is an insulator in a normal operating state, but when the lightning surge voltage is applied to the circuit, a current is caused to flow and the voltage is suppressed to protect the semiconductor element 1. Is. Further, this AK arrester is a ZnO having an operation starting voltage higher than the operating voltage and having a lightning surge current withstanding capacity found in the system.
The element is used. However, since the ZnO element has the voltage-current characteristics as shown in Fig. 3, if a lightning surge current of several kA flows into the arrester 3 between A and K, several kV will develop between its terminals.
Voltage will be generated.
If kA, V is across the terminals of arrester 3 between AK
A limiting voltage of about _10kA = 6.0kV will be generated.

Since this voltage is directly applied to the semiconductor element 1, when the rated voltage V _n of the semiconductor element 1 is 4 kV, for example, one AK as shown in FIG.
The number of forward and reverse series of the semiconductor element 1 is 2 with respect to the inter-stage arrester 3, and 4 kV × 2 = on the side of the semiconductor element 1 arranged in the forward and reverse series.
Additional 6.0k by providing the rated voltage _V'n of 8kV
It was designed to withstand the V voltage limit. As described above, generally, the number of series of the semiconductor elements 1 is determined by the limiting voltage of the AK arrester 3. Therefore, when the protection range is wide, the limiting voltage becomes high. The number of forward and reverse series of the semiconductor element 1 is increased, resulting in an increase in size of the device and an increase in manufacturing cost.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and reduces the number of forward and reverse series of semiconductor elements to reduce the device size and manufacturing cost. It has been completed to provide a protection method.

[0006]

SUMMARY OF THE INVENTION The present invention, which has been made to solve the above problems, provides an input side and an output side of a semiconductor device for a power system device in which an AK arrester is attached in parallel with a semiconductor element. Connect the earth arresters,
When a lightning surge current flows, most of the lightning surge current is caused to flow to the ground through the ground-to-ground arrester to suppress the terminal voltage of the AK arrester.

That is, according to the present invention, as shown in FIG. 1, a ground-to-ground arrester composed of ZnO elements is provided on the input side and the output side of a semiconductor device (thyristor stack) in which semiconductor elements 1 such as thyristor elements are connected in forward and reverse series. Connect 4 and 5 respectively. Further, as in the conventional case, a snubber circuit 2 including a resistor and a capacitor and an AK arrester 3 are connected in parallel with each semiconductor element 1. The ground-to-ground arresters 4 and 5 are provided on the input side and the output side of the semiconductor device, respectively, in order to cope with whichever lightning surge current enters. Further, depending on the wiring method of the semiconductor device, the earth-ground arrester may be installed only on the input side.

[0008]

The semiconductor device of FIG. 1 described above is used by being connected to the line of the electric power system, and since the AK arrester 3 is an insulator in a normal operating state, the semiconductor device 1 The switching operation can be performed by However, when a lightning surge current enters the semiconductor device through the line of the power system, the earth-to-earth arrester 4 or 5 instantly conducts due to the earth-to-earth voltage, and most of the lightning surge current that invades from the line to the earth. It will be washed away. Therefore, the current flowing through the arrester 3 between A and K is 1mA.
Below, the limiting voltage of the AK arrester 3 becomes 3 kV or less and 4 kV or less, which is the rated voltage V _n of the semiconductor element 1.
As a result, the number of series of semiconductor elements 1 does not have to be 2 as in the conventional case, and the number of forward and reverse series can be set to 1 as shown in FIG.

[0009]

As described above, according to the present invention, the earth-to-earth arrester is connected to each of the input side and the output side of the semiconductor device, and most of the lightning surge current flows to the earth through the earth-to-earth arrester. As a result, the voltage across the terminals of the AK arrester is suppressed, so that the limiting voltage of the AK arrester can be made _{equal to} or lower than the rated voltage V _n of the semiconductor element. Therefore, the number of forward and reverse series of the semiconductor element 1 can be reduced as compared with the conventional one, and the device can be downsized and the manufacturing cost can be reduced. Therefore, the present invention greatly contributes to industrial development as a semiconductor element protection method that solves the conventional problems.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a conventional example.

FIG. 3 is a graph showing voltage-current characteristics of a ZnO element.

[Explanation of symbols]

 1 semiconductor element 2 snubber circuit 3 AK arrester 4 earth arrester 5 earth arrester

Claims (1)

[Claims] 1. An earth-grounding arrester is connected to each of an input side and an output side of a semiconductor device for a power system device in which an AK arrester is installed in parallel with a semiconductor element, and when a lightning surge current enters, A method for protecting a semiconductor device, characterized in that a voltage between terminals of an A-K arrester is suppressed by causing most of the current to flow to the earth through an inter-earth arrester.