Frame circuit breaker manufacturers feel that when choosing a product, first you need to select the style and number of poles of the frame circuit breaker according to the application, then the rated current of the breaker according to the maximum operating current, and finally the type of tripper, type of accessories and specifications according to the need.

Firstly, the specific requirements for selecting a frame circuit breaker are as follows.

1. The rated operating voltage line rating of the circuit breaker.

2. Circuit breaker rated short-circuit breaking capacity circuit calculated load current.

3. The rated short-circuit breaking capacity circuit of the circuit breaker the maximum short-circuit current that may occur in the circuit.

Usually calculated as the effective value

4. Short relative short-circuit current at the end of the line 1.25 times the instantaneous or short delayed tripping set current of the circuit breaker.

Circuit breaker low voltage trip rated voltage equal to line rated voltage.

6. The rated voltage of the circuit breaker's separator is equal to the control power supply voltage.

7. The rated working voltage of the electric drive mechanism is equal to the control power supply voltage.

8. When circuit breakers are used for lighting circuits, the instantaneous set current of the electromagnetic trip is normally taken to be 6 times the load current.

9. When using circuit breakers as short-circuit protection for individual motors, the instantaneous tripper setting current is 1.35 or 1.7 times the motor starting current.

10. After selecting the type and rating of the circuit breaker for the first time, it should work with the protective characteristics of the parent switch to prevent tripping and extending the scope of the accident.

11. When using frame circuit breakers as short-circuit protection for several motors, the set current of the instantaneous tripper is 1.3 times the starting current of the largest motor and the operating current of the remaining motors.

When using a circuit breaker as the main switch on the low voltage side of a distribution transformer, the cut-off capacity must be greater than the short-circuit current value on the low voltage side of the transformer and the rated current of the tripper must not be less than the rated current of the transformer. The short-circuit protection set current is usually 6-10 times the rated transformer current and the overload protection set current is equal to the rated transformer current.