Experimentation of an Electric Machine Technology Demonstrator Incorporating Direct Winding Heat Exchangers

A novel advanced cooling technique for electric machines, which is termed the direct winding heat exchanger (DWHX), is presented. This technique uses a microfeature enhanced heat exchanger that is inserted between the stator winding bundles. The DWHX is innovative, with the capability of generating large heat transfer coefficients, i.e., ~30 000 W/m² · K, due to the small channel size and microfeatures. This cooling technique significantly reduces the thermal resistance from the stator windings to the ambient. The cooling technique is explained in detail, and an initial DWHX technology demonstrator electric machine is presented. The technology demonstrator is shown to be capable of steady current densities in excess of 24.7 A/mm² and transient current densities in excess of 40 A/mm² for class F insulation.