LIQUID COOLING THE ROTOR OF AN ELECTRICAL MACHINE

At least one liquid coolant passage is disposed within at least a pair of pole bodies in an electrical machine rotor. The liquid coolant passage is thermally coupled to pole loss heat caused by eddy currents and/or wilndage in the radially outermost portion of the rotor pole bodies. A rotatable liquid transfer coupling is fluid connected with the liquid passage(s) for transferring liquid coolant to and from the coolant passage(s) during machine operation. Preferably, a liquid coolant passage is included in each of N circumferentially spaced magnetically permeable pole bodies on the rotor. It is also preferable to include additional liquid coolant passages thermally coupled primarily to rotor windings within each coil slot of a typical rotor and fluid connected (either in parallel or in series) with the pole body liquid coolant passages.