(1) The rated voltage and rated current of the low-voltage circuit breaker shall not be less than the normal working voltage of the line and the calculated load current.
(2) The setting current of the thermal trip should be equal to the rated current of the controlled load.
(3) The instantaneous trip setting current of the electromagnetic trip should be greater than the peak current that may occur during normal operation of the load. The circuit breaker for controlling the motor, its instantaneous trip setting current can be selected as follows:
Iz≥KIst
Where: K is the safety factor, which can be 1.5~L7; Ist is the starting current of the motor.
(4) The rated voltage of the undervoltage release shall be equal to the rated voltage of the line.
(5) The limit breaking capacity of the circuit breaker shall not be less than the maximum short-circuit current of the circuit.