Innovation and reliability-BR´s experience [auxiliary power supply]

Prior to 1970, auxiliary power supplies on BR loco hauled coaches such as the Mk1 coach were produced by means of belt driven generators. In 1970, the Mk1 motor alternator (MA) set was introduced into service. This provided a much more stable supply and was a great step forward. Over the next ten years many improvements were made in performance culminating with the Mk12 MA set in 1980. When BR were next procuring stock in the late 80´s, static inverters were being introduced into service throughout the world and offered the benefits of zero maintenance, better regulation and, potentially, higher reliability. The author examines the reliability aspects of both MA sets and static inverters to show whether this potential for higher reliability has actually been realised. The first part of the paper looks purely at MA sets, their reliability and some technical reasons for unreliability. The second part of the paper gives the background to the reliability of static inverters on BR and the final part discusses the experience with static inverters and some of the lessons learnt