Machine Parts

It is used for determining the interrupting capacity of a circuit breaker or fuse employed to protect the primary of a transformer. Example : Determine a minimum circuit breaker trip rating and interrupting capacity for a 10 KVA single phase transformer with 4% impedance, to be operated from a 480 volt 60 Hz source. Calculate as follows: Normal Full Load Current = Nameplate Volt Amps 10,000 VA __________________ = __________ =                             Line Volts 480 V                                                           20.8 Amperes Maximum Short Circuit Amps = Full Load Amps 20.8 Amps _____________ = _________ =      4%                           4% 520 Amps The breaker or fuse would have a minimum interrupting rating of 520 amps at 480 volts. Example: Determine the interrupting capacity, in amperes, of a circuit breaker or fuse required for a 75 KVA, three phase transformer, wit