calculating instantaeous trip breakers and inverse time breakers
calculating instantaeous trip breakers and inverse time breakers
(OP)
Good morning,
I'm calculating the size of an Instantaneous or a inverse time breaker for a 200 hp motor, according to NEC 430.52 I'm to multiple my FLA by 1100% for instantaneous and 250% for inverse time. PLease correct me if I'm wrong.
221(fla) X 11.00= 2431 instaneous trip breaker
221(fla) X 2.5= 552.6 inverse time breaker
I'm assuming these has standard size as fuses do.
thank you for your help
2571
I'm calculating the size of an Instantaneous or a inverse time breaker for a 200 hp motor, according to NEC 430.52 I'm to multiple my FLA by 1100% for instantaneous and 250% for inverse time. PLease correct me if I'm wrong.
221(fla) X 11.00= 2431 instaneous trip breaker
221(fla) X 2.5= 552.6 inverse time breaker
I'm assuming these has standard size as fuses do.
thank you for your help
2571





RE: calculating instantaeous trip breakers and inverse time breakers
RE: calculating instantaeous trip breakers and inverse time breakers
Subject to cable sizing of-course I would normally use a 400A thermal magnetic breaker for a 150kW / 200hp motor.
Some breakers provide adjustments for both the themal and magnetic/instantaneous trips and this can be very usefull. Others may provide adjustments for thermal trips only, and generally on these I have found that the magnetic/instantaneous trip occurs somewhere in the range of 11 to 13 x rated current.
Specs will vary between manufacturers. I would therefore suggest your supplier of circuit breakers is in the best possible position to advise you further.
Regards,
GGOSS