GB967623A - Improvements in and relating to brush gear for carrying current in dynamo-electric machines - Google Patents

Abstract

967,623. Cooling brush-gear. C. A. PARSONS & CO. Ltd. May 24, 1961 [May 31, 1960], No. 19189/60. Heading H2A. The brush-gear in a dynamo-electric machine, for example the slip-ring brush-gear in a turbogenerator, is liquid cooled. In a first embodiment, Fig. 1, the housings 2 for the brushes are surrounded by a channel 3 through which water is circulated by a pump, inlet and outlet connections being provided at 4 and 5, respectively. The inner surfaces in contact with the liquid may be provided with fins to improve heat transfer. Fig. 4 shows the arrangement of the brush boxes of Fig. 1 in a dynamo-electric machine. Each brush box is attached to a respective bracket 10, the brackets in turn being supported on a plate 12. The boxes are connected in parallel with supply and discharge pipes 8, 9 for the cooling liquid. Cooling may alternatively be effected by the evaporation and subsequent condensation of the cooling liquid in a closed system. In Fig. 5 the brush box 16 and bracket 17 therefor are hollow with the cavities therein in direct communication. The cavities are filled with vaporizable liquid to a level above the brushes 19 as may be seen through the inspection window 21. The heated liquid vaporizes and rises into the cavity within the bracket 17 where it is cooled by a gas such as nitrogen, hydrogen or argon circulating over the outer surface provided with fins 22, a cooling gas other than air being used to reduce oxidation of the brushes. This, however, necessi- _ tates sealing the brush gear and to avoid the need for frequent access thereto, brushes at least 6 inches long and constant tension springs 23 are used. The voltages developed across resistors 24 in series with the leads 25 are monitored to check that no brush is carrying an excessive current. Instead of using a plurality of sealed brush boxes a common condenser may be used for a plurality of boxes, the condensate being returned to the boxes either under gravity or by a pump. In a further alternative solid brush boxes may be used, the brushes being cooled by liquid flowing through flattened tubes brazed to the boxes. As the cooled brush gear permits a heavier current flow, conductors of increased current-carrying capacity leading to the brushes are needed. This may be achieved by interposing a graphite or copper-graphite sleeve between each brush and the corresponding wall of the brush box, current then passing directly from the brush through the sleeve to the brush box, Fig. 12 (not shown). Alternatively, in machines in which the leads to the brushes carry direct current, thermo-electric cooling of the leads may be employed, Fig. 11 (not shown).