Experiences from Development and Operation of Switch Mode Power Supplies for Feeding of Electronic Telecommunication Equipment and Charging of Stationary Pb-Batteries

The power supply division at Standard Telefon og Kabelfabrik A/S (STK) has developed a range of primary switched power supplies for 48V telecommunication equipment. The design of the largest rectifier, HFC 48/200, a 200A unit, was presented on INTELEC -83 in Tokyo by Mr. I. Narvhus. This paper deals with the experiences gained from the development and operation of this unit. The HFC 48/200 has been in production since 1985. Approx. 120 units are in operation as per March-87, feeding ITT1240 digital exchanges in Norway. The largest plant installed consists of 18 rectifiers, i.e. 3600A. The main subjects discussed are as follows: Design and specifications. Experiences with the chosen design, presented at INTELEC-83, emphasizing the transistor chopper, internal noise problems and the control circuits for ripple regulation and parallel operation. The HFC 48/200 meets or exceeds all the Norwegian Telecommunications Administration (NTA)s requirements. EMC. General considerations about EMI problems in switch mode power supplies (SMPS). Mains and output EMI filtering of SMPSs feeding telecommunication equipment. Measurements of EMI on the HFC 48/200 and HFC 48/33. Operational experience. The designs chosen for the transistor chopper and base drive circuits have proven its reliability. Both experiences concerning harmonic distortion on the mains and parallel operation are discussed.