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.