Capacitor Start, Induction Run Motors

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Picture of a capacitor start, induction run (CSIR) motor. Notice the start capacitor is mounted on the top of the motor.The capacitor start, induction run motor (CSIR) is a split-phase motor with a starting capacitor connected in series with its start winding. This modification to the split-phase motor’s design is accomplished when the motor is manufactured, so the capacitor start motor is a separate choice in the manufacturer’s catalog when the motor is being specified and selected for the application. Since the CSIR motor can provide more starting torque than the split-phase motor, it would be selected for direct-drive and other applications that require more power during startup. Fig. 2 (right) shows a picture of a typical CSIR motor with the start capacitor mounted on top of the motor. The start capacitor is about the size of a small orange juice can. The case for the start capacitor is made of plastic.

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Electrical Diagram for a CSIR Motor