circuit breaker

As a rule-of-thumb, the starting current of a motor is of the order of 5x the full load current. A breaker for this service has to have a higher making capacity in order to delay its destruction by making current.

For making capacity , the possibility of a circuit breaker being closed on a dead short is taken into account . The capacity of a cb to make current depends upon its ability to withstand effects of electromagnetic forces . The maximum force in any phase is a function of the square of peak making current . The making current is the peak valve of maximum current wave , including dc component in the first cycle of the current after the circuit is closed by the breaker . The breaker capacities are quoted under specified conditions of severity - power factor , recovery voltage , and rate of recovery voltage . As a general rule , rated making capacity is 1.8 * 1.14 * rated symmetrical breaking capacity .