High power motor over-voltage protection device

Abstract

The related over-voltage protector for high-power motor comprises: three ZnO arresters with cathode paralleled together and connected to ground terminal and anode connected to three-phase terminal, three groups of R-C devices with two ends connected to ground terminal and arrester another end respectively. This invention can reduce damage rate of high-power motor and transformer to 2%.

Description

technical field [0001] The invention relates to a high-power motor overvoltage protection device. Background technique [0002] With the development of the metallurgical industry, especially the development of iron and steel enterprises, the power of air compressors and electric furnaces is increasing, and the capacity of the corresponding motors and transformers that supply power to electric arc furnaces is increasing, generally reaching more than 6000kVA. Air compressors The motor of the electric arc furnace is frequently interrupted, and the transformer powering the electric arc furnace is cut off 18-36 times a day without load. No-load current is easy to generate current-carrying overvoltage, which has been accumulated for many years. During the operation, the voltage affects the insulation of the motor and transformer, resulting in damage to the motor and electric arc furnace transformer. For example, the applicant had 6 electric arc furnace transformers in 1987. Due to...

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Problems solved by technology

[0002] With the development of the metallurgical industry, especially the development of iron and steel enterprises, the power of air compressors and electric furnaces is increasing, and the capacity of the corresponding motors and transformers that supply power to electric arc furnaces is increasing, generally reaching more than 6000kVA. Air compressors The motor of the electric arc furnace is frequently interrupted, and the transformer powering the electric arc furnace is cut off 18-36 times a day without load. No-load current is easy to generate current-carrying overvoltage, which has been accumulated for many years. During the operation, the voltage affects the insulation of the motor and transformer, resulting in damage to the motor and electric arc furnace transformer. For example, the applicant had 6 electric arc furnace transformers in 1987. Due to the voltage The overvoltage electric arc furnace transformer was damaged 20 times, of which the winding and porcelain bottle were damaged 11 times, and the overvoltage damage rate reached 55%. Due to overvoltage, the cable connecting the transformer and the electric arc furnace also exploded many times. 8 motors were also damaged due to voltage overvoltage

In order to prevent the vacuum switch from cutting off the no-load current to generate overvoltage, a zinc oxide arrester is connected in parallel between the three-phase vacuum switch and the transformer as an overvoltage protection device for the electric arc furnace voltage. The zinc oxide arrester is a nonlinear element. Its resistance is very large, but when overvoltage occurs, the resistance value presented is very small. Although the current is released from the ground when the vacuum switch cuts off the no-load current to generate overvoltage, the power grid releases energy to the ground to protect the vacuum switch and the motor. 1. The transformer avoids overvoltage damage, but due to the frequent opening and closing of the vacuum switch, the zinc oxide arrester was frequently switched on and off before the modification. For a 4000kW electric arc furnace power supply equipment, the zinc oxide arrester was switched on and off 20 times a year, and the zinc oxide arrester was quickly fatigued. Damage, loss of protection for vacuum switches, motors and transformers, the damage rate of motors and transformers reaches 50%

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