Characteristics of a single-phase shunt commutator motor with an improved field phase-correction circuit

The paper describes a single-phase motor having shunt characteristics. Speed adjustment is available by field rheostat, or by variation of armature voltage, exactly as for a shunt-wound d.c. motor. At each speed setting, the power factor remains unity or slightly leading over the whole range from no-load to full-load. Commutation conditions are favourable, and the losses are not seriously greater than those of a d.c. motor. Operation is simplified by the fact that the motor is analogous in main principles to the shunt-wound d.c. motor, while manufacture is facilitated because design and construction closely follow the serieswound a.c. motor. The vector relationships in the motor are investigated, and appropriate control circuits developed. Design factors affecting the rating of the condenser required in the field circuit are discussed. The speed regulation and maximum torque are evaluated in terms of the comparable values under d.c. operation. Tests of the theory and performance of the motor are described.