This standard covers enclosed low-voltage ac power circuit protectors that are manually operated or power operated. Addressed are circuit protectors of the stationary type with 2-pole or 3-pole construction, having one or more rated maximum voltages of 508 V and 254 V rms for application on systems having nominal voltages of 480 V and 240 V RMS. The circuit protectors considered are furnished with current-limiting fuses such that the entire device is suitable for application on circuits capable of delivering not more than 200 000 An rms symmetrical short-circuit current. Service conditions and ratings are discussed, and the functional components of the circuit protectors are described. Temperature limitations and classification of insulating materials are covered. Insulation(dielectric) withstand voltage requirements are specified, and an application guide is given. Test procedures are also specified.