GB1470082A - Electromagnetic machine rotor assembly - Google Patents

Abstract

1470082 Cooling dynamo-electric machines SBW ENGS Ltd 24 Jan 1975 [31 Jan 1974] 04435/74 Heading H2A The rotor of an electric motor is cooled by having a heat pipe extending axially therein, with its evaporating portion within the rotor and its condensing portion outside the rotor. The rotor of a two-pole D.C. commutator motor has a shaft 14 mounted in bearings in the housing. The active part of the rotor is enclosed by a heat shield and the shaft 14 has an axial bore 15 extending through the active region to a tapered portion 17 outside the housing which portion carries a hub with cooling fins (21, Fig. 1, not shown) secured by a nut (23) on a stub shaft (24). The bore is filled with water through a duct 24 which after exhaustion of all air is sealed. The heat generated in the rotor vapourizes the water which moves to the tapered portion and there condenses due to the cooling action of the fins (21), which action is improved by allowing passage of air through apertures (22) therein and/or by making the inner surface of the tapered portion 17, fluted, ridged or by embedding copper spheres therein (Figs. 3-5, not shown). The water condenses on the inner surface and is forced back to the evaporating portion by the centrifugal force acting along the tapered wall. The bore has a fusible plug 7 for preventing failure due to overpressure during extreme heating. The tapered portion 17 will eventually accumulate pockets of incondensible gas, which must be removed. The stub shaft 29 is thus made hollow (Fig. 3, not shown) and is closed either by an annular end cap which leaves an annular chamber connected to the condensing portion in which the gases collect, or the end cap has an external annular recess coaxial with an axial bore in which the gases collect. The presence of the gases is detected by temperature measurements in the recesses of the caps, since there is a large temperature dinerence across the vapour/ gas boundary. To help cool the windings, copper discs are spaced axially along the windings to conduct heat to the shaft or to subsidiary pipes containing water which extends through the windings and communicate with the evaporating portion (Fig. 6, not shown).