Study on Failures and Reliability Aspects of VFDs in Oil Refinery

This paper discusses the failure of Variable frequency drives (VFDs) in various units in oil refinery on the basis of historical data. VFDs are extensively used in Oil and Gas industry, particularly refineries can save substantial energy by using VFDs to regulate the speed and by controlling pump discharge flow for various processes. Variable frequency drives also functions as a soft starter of ac motors. VFDs are also used for accurate process control, that lead to economic operation of the process plants. However, VFD failure can result into massive interruption in the process flow and associated losses other than cost of unscheduled maintenance. The VFD failures in industry have been broadly classified in five categories (1) Failure of components in converter/inverter sections (2) Failure of wrongly designed auxiliary power supply units (3) Failure of connected power cables and fault in external power system (4) Failure of cooling system of VFD panel (5) Failure during system upgradation.