Proposed standard for transients on the 48V rail

This paper addresses the transients that may be experienced on the -48 V rail, with the objective of establishing a practical transient waveform, suitable as a design requirement for the equipment providers and acceptable to the equipment users. After an introductory description of the transient phenomena that take place in the power distribution circuits when a shortcircuit-type fault occurs, the paper reviews the parameters that determine the characteristics of the transients likely to occur in the field. Both experimental data and data produced by various telecommunications companies and standards organizations in their efforts to characterize and specify the transient requirements for their equipment an used to further characterize the transients. The paper then proposes a transient waveform suitable to serve as a common standard for the designer, the tester, and the equipment user. Further, the paper proposes an approach suitable for specifying the transient requirements imposed on the de distribution and on the dc/dc converters or point-of-use power supplies fed by the de distribution. The paper also proposes a test method suitable for verifying that the proposed standard is met. Comparing the advantages of using such a standard waveform and test method with the diversity of approaches currently in use, the paper concludes that a global standard that fully defines the interface between power equipment and telecommunication equipment must include a transient requirement and would directly and immediately benefit the global telecommunication industry.