The aim of this paper is to analyze the reliability of Variable Frequency Drives (VFD) when used to control condensate pump motor in a nuclear power plant. IEC 60812 system reliability analysis procedure for Failure Mode and Effects Analysis (FMEA) was used to determine the potential failure modes for VFD and its effects on the operation of the condensate pump motor. In addition, Electrical Transient Analysis Program (ETAP) was used to simulate the performance and evaluate system reliability indices of the VFD for APR1400 auxiliary power system. The objective for adopting these two approaches is to use the FMEA for comprehensive identification and evaluation of unwanted effects of VFD malfunction on the condensate pump operation; and the ETAP was used to quantify the impact of VFD operation on system reliability indices. From the FMEA model, the Insulated Gate Bipolar Transistor (IGBT) and the motor stator winding were identified as the components with high susceptibility to failure. The overall reliability assessment showed that VFD failure effects are generally incipient. Average system availability increased marginally when VFD was used instead of the existing throttle valve for condensate flow control.
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