GB469092A - Improvements in and relating to dynamo-electric machines - Google Patents

Abstract

469,092. Dynamo-electric machines. BRITISH THOMSON-HOUSTON CO., Ltd. Oct. 12, 1935, No. 28215. Void. Convention date, Oct. 12, 1934. [Class 35] Cores; exciting.- A dynamo - electric machine, particularly a welding generator, has an n pole armature and a 2n pole field structure in which the flux is varied by armature reaction, the poles comprising a set of main poles 15 and a set of cross-poles 16 having exciting windings 17, 18 connected in series so that the voltage induced in the windings on one set of poles by reason of their magnetic coupling with the armature windings is substantially neutralized by the voltage similarly induced in the windings on the other set. As shown, the air gap 20 under the main poles 15 is twice that 21 under the cross poles 16 and accordingly, the number of turns of the windings 17 is twice that of the windings 18. Armature reaction acting in the direction AR has a component AM assisting the main pole flux, and a component AC opposing the cross pole flux so that a drooping characteristic is obtained. A series winding 22 may be placed on the cross poles to assist the armature reaction and this winding may be tapped to give any rate of change in the voltage across the brushes 13, 14 per ampere change in the load current. In a modification, the exciting windings 17, 18 are fed from the brush 13 and an auxiliary brush so that the generated voltage is due to the flux of the main poles. This flux is maintained constant by saturation in the armature, the main poles being provided with flux shunts and a series winding acting in the same direction as the winding 17. By increasing the turn ratio of the windings 17, 18 the size of the magnetic circuit may be reduced.