Patent GB-886378-A (GB)
Title: Improvements relating to the cooling of electrical machinery
IPC: H02K9/00
Filed: 1957-12-12
Abstract: 886,378. Cooling dynamo-electric machines. LAING, N., ECK, B., and LUDIN, L. Dec. 12, 1957, No. 29464/61. Divided out of 886,376. Class 35. Various component parts of a dynamo-electric machine are cooled by means of a ring of impeller blades which extend axially of the rotor and which, in conjunction with a fixed air-flow guide, cause a vortex to be set up which forces air laterally through the impeller, i.e. in at one side and out at the other. The invention may be applied to a drum or disc-type commutator, slip-rings or to the whole machine. The principle is described as applied to a drum-type commutator in Fig. 1, in which the commutator bars A are partly cut and bent inwardly at intervals to form the blades 3 lying in axially spaced radial planes. The air flow is directed as shown by guides 8 and 9 extending the length of the rotor. The guide body 9 is provided with a concave surface 9a which causes a Rankine vortex V<SP>1</SP>, which in turn sets up the through-flow, this being concentrated at M<SP>1</SP>F<SP>1</SP> close to the vortex. An auxiliary body 9b of various shapes may be added for use in throttling the air flow. This is achieved either by a movable valve-flap in the vortex path between the bodies 9a, 9b, or by angular adjustment of the body 9b itself, the path between the bodies being blocked by a baffle. If desired, the body 9b may be spring- restrained to produce a pulsating effect. Alternatively, control may be achieved by butterfly valves in the main intake path. Air-flow between slip-rings may be provided in a similar manner. In a modification, Fig. 16, the air-flow guides 161-163 are inside the ring of blades, the vortex V<SP>1</SP> being as before, and control flaps 167 on spindle 168 is provided to throttle the through flow. This form of the invention may be used for passing air across the face of a disc-type commutator, the blades 3 projecting axially from the commutator face at its periphery, and the axial brushes and rotor bearing being accommodated in holes in the guide bodies. A squirrelcage rotor may have similar blades projecting from its end rings, the air-flow guides being either inside or outside these blades, as described above. In the case of a motor having an external rotor, the guides are mounted on the internal stator. Fig. 28 shows the application of the form of the invention shown in Fig. 1 to the cooling of a large machine by means of air circulated across both stator and rotor through aligned radial planar ducts. The rotor sections 273a are spaced by blade-shaped elements 283, and the stator sections 274a are spaced by airflow guide elements of similar profile to those shown in Fig. 1. These are displaced 30 degrees in successive ducts. The cooling air passes through the machine from chamber 276a to chamber 276b, these chambers being separated by a pair of helical walls 279 forming part of the machine casing. Various alternative arrangements of guides and baffles to give flow in various directions are described. The arrangement for a reversing machine is also described. The impeller blades may be shaped and notched at their leading edges to induce turbulence. Specifications 876,611 and 876,612 also are referred to.