This part of ISO 10924 specifies circuit breakers with rated voltage of 450 V for use in road vehicles. It establishes, for this circuit breaker type, the rated current, test procedures, performance requirements and dimensions.This part of ISO 10924 is intended to be used in conjunction with ISO 10924-1 and with ISO 10924-2. The numbering of its clauses corresponds to that of ISO 10924-1 whose requirements are applicable, except where modified by requirements particular to this part of ISO 10924.This part of ISO 10924 is applicable to circuit breakers with a rated voltage of 450 V d.c., a current rating of no greater than 300 A and a breaking capacity of 6 000 A.