Phase change cooling [for electric traction]

Phase change or evaporation cooling of high power semiconductors has been used within the traction industry for a number of years. The essence of the principle is to use the evaporation of a fluid to transport heat from the semiconductor devices to a suitable heat exchanger. The ability to do this provides cooling which exceeds the capability of all other cooling systems and results in very stable device operating conditions. The author describes how the physical construction can be made relatively small in immersion based systems which use the dielectric properties of the fluid and vapour for insulation. This in turn permits the designer to extract the maximum utilisation from the power devices and achieve higher ratings per unit volume