3 Phase Circuit Breaker Sizing Calculator. Cable sizing software select size and manage your power cables using mycableengineering. Lv and mv cables up to 33 kv with current capacity in accordance with bs 7671 era 69 30 and iec 60502.
If we use a 100a circuit breaker for 30a circuit it wont protect the circuit from fault currents and may burn and damage the device as more than 30 amperes current won t trip the circuit breaker. If your total 3 phase load in a 480v system is 50 000va what size breaker do you need. Breaker size must be rated for a minimum of 125 of the full load current of the motor it is protecting rounded up to the next standard breaker size.
It s always required to have the motor data especially the power rating in hp and supply 3 voltage.
It s always required to have the motor data especially the power rating in hp and supply 3 voltage. The next size up is 70a. For example the full load current of a 5 hp motor at 460v is 7 6 amps. In short we must use the proper size of circuit breaker according to the device i e.
