GB150357A - Improvements in and relating to dynamo electric machines - Google Patents

Abstract

150,357. British Thomson - Houston Co., (General Electric Co.). April 17, 1916. Exciting; cores.-A dynamo-electric machine, more particularly adapted for use on an automobile as an engine-starting motor and as a generator of practically constant electromotive force for lighting and battery-charging, is provided with three field-magnet windings 21, 26, 27. The winding 21 is distributed in slots in two opposite quadrants of the field structure 20 and is arranged with its axis at an angle of forty-five electrical degrees to that of the armature winding 22; the winding 21 is connected in series with the armature winding. The winding 26 is a magnetizing- winding and has its axis at right-angles to that of the armature winding; the winding 27 acts in opposition to the winding 26 and is connected between an auxiliary brush 28 and the nearer main brush 24. The winding 26 is either a pure shunt winding, as shown in Fig. 8, or it may be connected between the brushes 28, 34. When the machine operates as a motor, the effect of the armature current predominates and the winding 21 gives the starting characteristics of a compensated series motor, the effect of the windings 26, 27 being negligible. When operating as a generator, the demagnetizing effect of the winding 27 increases as the speed rises so that the voltage is kept fairly constant. The winding 27 embraces only a portion of the polar arc occupied by the winding 26, the flux threading the portions 30 remaining substantially constant. To improve commutation, wide slots 25 are provided for the reception of the coils 26 etc.; the slots 25 are preferably closed by non-magnetic wedges 31, while the other slots in the field magnet are closed by magnetic wedges 32.