This standard defines the preferred ratings for low-voltage AC (635 V and below) power circuit breakers, general purpose DC (325 V and below) power circuit breakers, heavy duty low voltage DC (3200 V and below) power circuit breakers, and fused (integrally or non-integrally) low voltage AC (600 V and below) power circuit breakers.

This standard provides the preferred ratings for low-voltage ac (635 V and below) power circuit breakers,fused low-voltage ac (600 V and below) power circuit breakers, general purpose dc (325 V and below) power circuit breakers, and low-voltage dc (3200 V and below) power circuit breakers.

This standard provides preferred ratings to establish a uniform basis of product design and testing for low-voltage ac and dc power circuit breakers. The ratings in this standard are preferred but are not restrictive. Manufacturers may choose to offer, and users may elect to require, ratings which differ from those in this standard.