Reliability Estimates for Power Supplies

This paper presents results of a task to analyze operating experience data to determine the combined 'fail to operate on demand' and 'fail to continue to run' failure rate for the toroidal field coil power supply at the DIII-D fusion facility. This large power supply is used in every plasma shot and has a considerable amount of operations data accumulated. Studying power supply reliability supports safety assessment, machine availability assessment and can potentially improve power supply performance. The DIII-D trouble report database was used to determine the number of power supply faults, system design descriptions supplied the power supply basic information, and operations data supplied the numbers of shots that have been performed. The power supply fail to operate failure rate was found to be 1.1E-02/operations hour. This reliability value compared well with the value from power supply data that has been analyzed from the Joint European Torus, and also compared very favorably with some particle accelerator power supply data