Liquid cooling the rotor of an electrical machine

An electrical machine having a rotatable rotor member comprising:

• electrical current conductors which produce heat during machine operation due to electrical current flow therein;
• magnetic flux conducting structure which also produces heat during machine operation due to induced eddy currents and/or windage losses therein;
• a first liquid coolant passage thermally coupled primarily to said electrical current conductor without being electrically connected therewith;
• a second liquid coolant passage disposed within and thermally coupled primarily to said magnetic flux conducting structure;
• and
• means for coupling in series the first liquid coolant passage and the second liquid coolant passage whereby, during machine operation, liquid coolant first passes through one of the first and second passages and before passing through the other of the passages.

An electrical machine having a cylindrical rotor rotatable about a central axis and including N circumferentially spaced magnetically permeable pole bodies which produce heat during machine operation due to induced eddy currents, said machine comprising:

• at least one liquid coolant passage disposed within at least one of said pole bodies and thermally coupled to said heat caused by eddy currents;
• and
• a rotatable liquid transfer coupling fluid connected with said liquid coolant passage(s) for transferring liquid to and from the coolant passage(s) during machine operation, and wherein the rotor includes:
• a field coil winding slot disposed between each pole body and extending radially inwardly from the rotor circumference;
• and
• a further liquid coolant passage disposed within each said winding slot and thermally coupled to electrical windings also disposed therewithin while being electrically insulated and separate from the windings.

An electrical machine having a rotatable rotor member comprising:

• electrical current conductors which produce heat during machine operation due to electrical current flow therein;
• magnetic flux conducting structure which also produces heat during machine operation due to induced eddy currents and/or windage losses therein;
• a first liquid coolant passage thermally coupled primarily to said electrical current conductor without being electrically connected therewith;
• a second liquid coolant passage disposed within and thermally coupled primarily to said magnetic flux conducting structure;
• and
• a rotatable liquid transfer coupling fluid connected with said first and second coolant passages for passing liquid coolant to and from said coolant passages during machine operation.

A method for cooling an electrical machine having a cylindrical rotor rotatable on a shaft about a central axis and including circumferentially spaced magnetically permeable salient pole bodies which produce heat during machine operation due to induced eddy currents, the rotor including electrical windings within axially elongated slots, said method comprising:

• pumping liquid coolant through an axially extending coolant tube defining a passage, the coolant tube being provided in each slot at a radially innermost portion of the slot whereby the liquid coolant is electrically insulated and separated from the windings;
• pumping liquid coolant though a passage which is within and thermally coupled primarily to said salient pole bodies and to said heat caused by eddy currents;
• and,
• transferring liquid coolant both to and from said passages during machine operation via a fluid coupling disposed at one end of said shaft.