This standard specifies requirements for semi-conductor direct d.c. convertors (d.c. chopper convertors) with regard to rated values, testing and performance characteristics.These requirements apply to all types of semiconductor direct d.c. convertors, i.e. d.c. to d.c. convertors without an a.c. link. The requirements of AS 1955, Parts 1 and 2, shall also apply to semiconductor direct d.c. convertors in so far as they are not in contradiction to the requirements herein.For some special applications, e.g. electric traction equipment, additional requirements may apply.NOTE: This standard may also be used for certain d.c. switches in control applications, if applicable.