RAM performance evaluation is considerd for a ship electric propulsion system, based on Current Source Inverter (CSI) drives. Steady state expressions of failure rate and repair rate for propulsion sub-systems are derived by the application of the Successive Reduction Method (SRM). Sensitivity analysis of these variables and of overall performance indexes (Reliability and Availability) is developed in two steps. First, the partial derivatives of the sub-systems repair and failur rates are computed with respect to the reliability parameters of the elementary componets, following a conventional deterministic approach. Second, probabilistic properties of the overall performance indexes are evaluated against the distributions of the failure and repair rates of the sub-systems, determined at the previous step. This procdure leads to an estimation of the risk and of the confidence ranges in evaluating overall performances, given the reliability parameters from the suppliers of the sub-systems.
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