What is an "HM" breaker?

posted in: Constant Current Products


Was this answer helpful?

Let us know!

"HM" is short for "High Magnetic Load," which typically means the internal trip delay is designed for use with transformers or other devices that have a higher than normal inrush current. Standard circuit breakers can suffer from nuisance tripping because their internal delay will occasionally see in-rush current as a fault whereas an "HM" breaker sees it as normal operation.

 

In-rush current occurs when power is first energized and only lasts a fraction of a second, and is most severe when components are "cold," therefore in-rush current will not trip a standard breaker every time.