NEWS & KNOWLEDGE

Plastic case Circuit Breakers (hereinafter referred to as circuit breakers) are usually used for power distribution and can also be used to protect motors. Under normal circumstances, circuit breakers can be used for infrequent line switching and infrequent motor starting. Circuit breakers used for power distribution are used to distribute electrical energy in the power distribution network and are used as overload, short circuit and undervoltage protection for lines and power equipment. Undervoltage protection also requires the installation of a shunt release.

Plastic case circuit breakers are classified according to different extinguishing media. Circuit breakers that use air as the arc extinguishing medium are called air circuit breakers (air switches); circuit breakers that use inert gas as the arc extinguishing medium are called inert gas circuit breakers. Circuit breaker (inert gas switch); A circuit breaker that uses oil as the arc extinguishing medium is called an oil circuit breaker (oil switch).

The main contacts of plastic case circuit breakers are manually operated or electrically closed. After the main contact is closed, the free trip mechanism locks the main contact in the closed position. The coil of the overcurrent release and the thermal element of the thermal release are connected in series with the main circuit, and the coil of the undervoltage release is connected in parallel with the power supply.

What principles should be followed when choosing a plastic case circuit breaker?

A plastic case circuit breaker is a mechanical switch device that can connect, carry and disconnect current under normal circuit conditions, and can also connect and carry a certain time and disconnect current under specific abnormal circuit conditions. In the design of civil buildings, low-voltage circuit breakers are mainly used for line overload, short-circuit, over-current, voltage loss, under-voltage, grounding, leakage, automatic switching of dual power supplies, and protection and operation of motors during operation. They do not start frequently. Principles In addition to complying with the basic principles of environmental characteristics of low-voltage electrical equipment, plastic case circuit breakers should also consider the following conditions:

1. The rated voltage should not be less than the rated voltage of the line;

2. The rated current and the rated current of the overcurrent release shall not be less than the calculated current of the circuit;

3. The rated short-circuit breaking capacity is not less than the short-circuit current in the line;

4. The selection of power distribution plastic case circuit breaker needs to consider the coordination of short-time closing and breaking capacity and delay protection level;

5. The rated voltage of the undervoltage release of the circuit breaker is equal to the rated voltage of the line;

6. When used for motor protection, the starting current of the motor should be considered when choosing a plastic case circuit breaker, and the motor should not run within the starting time.

- Mar 15, 2021-