The Capacitor Motor

Author: E.E. Kimberly

A split-phase motor may be provided with a capacitor (condenser), whereby the phase-splitting is accomplished more perfectly than is done by resistance and the starting characteristics are improved. See Fig. 21-5 (b). Such a motor is called a capacitor motor. Its construction is illustrated in Fig. 21-8. The starting torque obtained is 3 to 4 times the full-load running torque, and is usually about 30 per cent higher than the maximum running torque.

Fig. 21-8. Capacitor Motor

The starting-current inrush is 6 to 7 times the rated full-load current; but, because of the superior power factor provided by the capacitor, the inrush current is only about 60 per cent of that of a resistance split-phase motor of comparable rating. Any device which requires a single-phase motor of high starting torque, high efficiency, small slip, and quiet operation will be satisfactorily driven by this type of motor.