Interrupting rating of LV motor contactors

[Pitt123]

Do LV motor contactors have a small interrupting rating similar to the low rating of MV contactors?

 

[Jraef]

Do LV motor contactors have a small interrupting rating similar to the low rating of MV contactors?

"Interrupting rating" would not apply to a contactor, it is not a circuit protective device that would interrupt a fault, it is a control device. Contactors have a "withstand" rating, and more recently (if you are in North America) a Short Circuit Current Rating, or SCCR (which only applies to LV systems, so you can't make a comparison to MV ratings). In general, contactors by themselves have relatively low SCCR ratings, as in 5kA, as well as the Over Load Relay. That is why you have to be careful when making your own motor starter, because the contactors and OLR will be required to be tested in series with the protective device, i.e. breaker or fuses, in order to get beyond the 5kA limit. Fuses are usually not a problem because mfrs list them behind a CLASS of fuses, available from virtually any source. But with CBs, typically a mfr only lists them behind THEIR OWN breakers, not those of anyone else. To get an SCCR rating on a COMBINATION starter or contactor set, they can often get a much higher rating in series than the lowest individual component. So for example untested, a contactor is 5kA, an OLR is 5kA, a CB is 25kA, but the entire series combination, if tested by the manufacturer, may actually be rated for 65kA.

 

[Jraef]

Here is a link to UL's page that then links to most of the major mfrs so you can determine the exact series combination ratings.