The Capacitor Start Capacitor Run Motor has a cage rotor, and its stator has two windings known as Main and Auxiliary Windings. There are two capacitors in this method one is used at the time of the starting and is known as starting capacitor (C2). The other one is used for continuous running of the motor and is known as run capacitor (C1).
There are two designs:
(i) In one design, a single capacitor C is used for both starting and running . This design eliminates the need of a centrifugal switch and at the same time improves the power factor and efficiency of the motor.
(ii) In the other design, two capacitors C1 and C2 are used in the starting winding as shown in figure. The smaller capacitor C1 required for optimum running conditions is permanently connected in series with the starting winding. The much larger capacitor C2 is connected in parallel with C1 for optimum starting and remains in the circuit during starting. The starting capacitor C1 is disconnected when the motor approaches about 75% of synchronous speed. The motor then runs as a single-phase induction motor.
Characteristics
(i) The starting winding and the capacitor can be designed for perfect 2-phase operation at any load. The motor then produces a constant torque and not a pulsating torque as in other single-phase motors.
(ii) Because of constant torque, the motor is vibration free.
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