MOTOR DRIVE WITH HEAT PIPE AIR COOLING

An air cooled switching unit for a motor drive includes a plurality electrical switches and a plurality of heat pipe assemblies. Each heat pipe assembly includes a thermally and electrically conductive evaporator, a condenser, and at least one heat pipe extending between the evaporator and condenser. Each of the switches is abutted with an evaporator of at least one of the heat pipe assemblies for conduction of both electrical power and heat between the switch and the evaporator. Each heat pipe assembly further includes an electrically conductive base abutted with the evaporator, and the air cooled switching unit further includes a plurality of power lugs each connected to a base of a respective one of the heat pipe assemblies for input or output of electrical power to the base and the evaporator plate abutted with the base. Each heat pipe assembly includes at least one evaporator defined by a metallic plate. The condenser of each heat pipe assembly includes a plurality of parallel spaced-apart cooling fins. The at least one heat pipe of each heat pipe assembly includes a sealed pipe containing a phase-change material for transferring heat from said evaporator to said condenser. The at least one heat pipe includes a first end located in the metallic plate and a second end in contact with and extending through the cooling fins of the condenser. A temperature feedback system derives air flow velocity through the condenser.