Plant electrician

hello all i have a question relating to circuit protection. my understanding is that 99% of molded case circuit breakers are inverse time trip. I have several that say instantanous trip CB on them? and many more with nothing at all but the current rating on the handle. whats the best way to tell by looking at them?

Thanks
TL

Yes inverse time -just like with fuses. If the ratings are not on the unit itself then you will have to look up the factory manual / documentation.

Dan Bentler

It depends very much on the moulded case circuit breaker. I do not know if you are referring to small or larger ones.
I use a lot of Schneider MCCBs from about 63 amps up to 1600A or more and they all have separate trip units. There are many settings in the trip units with respect to current including instantaneous, long time, short time,earth leakage etcetera. Different trip units have different capabilities.