Circuit Breaker sizing for VFD and soft starter circuit?
Circuit Breaker sizing for VFD and soft starter circuit?
(OP)
Does anyone know of how to size the circuit breaker for VFD and soft starter circuit? The code does not mention anything about it. Normally VFD user manual will give the suggested circuit breaker size. But what about soft starter circuit?





RE: Circuit Breaker sizing for VFD and soft starter circuit?
JRaef.com
Eng-Tips: Help for your job, not for your homework Read FAQ731-376
RE: Circuit Breaker sizing for VFD and soft starter circuit?
Do you mean I can size the circuit breaker of soft starter circuit the same way as in full voltage starter?
RE: Circuit Breaker sizing for VFD and soft starter circuit?
JRaef.com
Eng-Tips: Help for your job, not for your homework Read FAQ731-376
RE: Circuit Breaker sizing for VFD and soft starter circuit?
Although starting current is reduced it is drawn for a longer period of time. The theoretical I squared t is the same in both cases.
Some people will select a smaller breaker on the basis that the start current will be lower and then suffer nuisance tripping.
Regards,
GGOSS
RE: Circuit Breaker sizing for VFD and soft starter circuit?
RE: Circuit Breaker sizing for VFD and soft starter circuit?
RE: Circuit Breaker sizing for VFD and soft starter circuit?
Best regards,
Mark Empson
http://www.lmphotonics.com
RE: Circuit Breaker sizing for VFD and soft starter circuit?
A specific recommendation from the manufacturer would be the only reason to do somthing different.