A motor drive or bus supply power conversion system includes a rectifier with at least one rectifier switch module for rectifying AC input power. A DC bus is connected to the rectifier and supplies DC output power. An optional inverter is connected to the DC bus and includes at least one inverter switch module for inverting the DC bus voltage to an AC output power. The at least one rectifier switch module and the at least one inverter switch module each include a base plate and a housing connected to the base plate. The housing defines an interior space that contains at least one semiconductor switch. Anti-corrosion features are provided including a conformal coating on printed circuit board assemblies, removable connector covers, dielectric grease coated connections, nano-coated fiber optic transceivers, and an exterior protective film wrap.