The Use of Phase Change Material for the Cooling of Electric Machine Windings Formed with Hollow Conductors

A phase change material (PCM) is a substance capable of storing or releasing large amounts of energy typically when melting or solidifying. The use of PCM is promising for the cooling of electric machines with high-load short transient duty, such as aircraft stator generators (S/G). During the starting phase, which lasts a couple of seconds, a substantial amount of heat has to be extracted from the machine windings, while the steady-state operation is less thermally constraining. In order to ensure sufficient cooling capabilities, PCMs should be placed as close as possible to the winding conductors due to their low thermal conductivity. This paper investigates a novel integration approach, where PCMs are placed inside hollow conductors (HCs). Numerical and experimental analyses have been completed on a range of hollow conductors filled with PCMs to gain a first insight into the benefits of this cooling method. Detailed descriptions of the proposed cooling technique have been supplemented with measured data from tests on a hollow conductor exemplar filled with PCM. An illustration of a practical use of the developed method on a helicopter turbine S/G is also presented.