High-speed compulsator stator thermal management

The compulsator stator armature winding includes multiple conductor layers. Each conductor layer is made of insulation wraps and transposed aluminum litz wire bundles with epoxy potting compound between the wires and the wire bundles. For a typical pulse-duty application, based on a room-temperature electrical loss calculation, the temperature rise in the aluminum winding is approximately 30 degreesC per shot. Adequate active cooling must be provided such that the stator insulation can survive thermally under a certain pulse repetition rate. The thermal management is quite challenging since the heat loss in the litz wires needs to be conducted through multiple insulations before reaching the coolant passages. As a result of the low equivalent thermal conductivities of the stator winding in the transverse direction, without compromising the overall structural integrity of the winding, the coolant passages have to be allocated as close as possible to the heat sources. For a given electric gun firing mission, four different cooling configurations have been investigated and analyzed by using water ethylene glycol mixture as an active liquid coolant. In this paper, thermal analysis cooling parameters, transient stator winding temperature distributions, and hot-spot temperature histories are presented, discussed, and compared.