GB643485A - - Google Patents

Abstract

643,485. Making dynamo-electric machines. BRITISH THOMSON-HOUSTON CO., Ltd. July 31, 1947, No. 20863. Convention date, July 31, 1946. [Class 83 (ii)] A method of treating a laminated magnetic core member having an electrically conducting winding cast into peripheral slots, comprising heating the member for a short time to a temperature slightly below the melting point of the cast winding and then rapidly cooling as by quenching. A plurality of circular laminations are assembled on an arbor 2 to form a core 1 with winding slots 3 and the whole is then dipped into a thin clay and water mixture and dried. This forms a thin insulating layer over the core. Any other thin insulating wash may be used. Aluminium is then cast around the core to form windings 5 in the slots 3 connected by end rings 4, after which the member is finished to the required dimensions by turning or grinding. This latter operation tends to smear the aluminium over and between the laminations, thus introducing core losses under normal running conditions and in order to correct this, the core is heated by high-frequency induction to a temperature slightly below the melting point of aluminium and is then rapidly cooled, as by quenching. It is stated that any metal which may have become embedded between the laminations becomes liquid and by surface tension is drawn back into the main body of metal in the slots. The heating is effected by means of a number of coaxial water-cooled induction-heating coils surmounted by a quenching spray ring.