GB379541A - Improvements in and relating to methods of insulating electric conductors - Google Patents

Abstract

379,541. Insulating dynamo-electric machines. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Fiene, M. E. ; Ballston Lake, New York, U.S.A.) Oct. 8, 1931, No. 28005. Convention date, Oct. 8, 1930. [Class 35.] Electrical coils such as the stator coils of a dynamo are insulated with paper, cotton, or other fibrous material which may be mixed with asbestos fibres. After winding the stator, inert inorganic filling material such as silica, preferably of 20-30 mesh, is introduced through openings 8 in end shields 4 to fill the space between the coil turns. To impregnate, the stator is placed in a bath 9 with a removable cover 10 and inlet and outlet pipes 11, 12, respectively, for the impregnating fluid. Valve mechanism 16 in a pipe 15 controls suction and pressure lines 17, 18 respectively. The bath 9 is exhausted of air and impregnating fluid such as sodium or potassium silicate is run in until the stator is covered. Suction is now cut off and pressure of about 100 pounds per square inch for one hour applied. The stator is then removed and baked in inert gas or a vacuum at a temperature, viz. 400‹ C., high enough to decompose to a stable compound the cellulosic material of the insulation and to set the impregnating fluid firmly to bind the conductors in place. A second impregnation and baking is carried out, and the coil may then be impregnated at a temperature between 100‹ C. and 600‹ C. with lead borate, lead chloride or sulphur so as to seal any pores which may be present.