The start capacitor stores electrons during one current alternation, then discharges the electrons into the start winding when the current alternates again. This delays the phase of the current and the magnetic field generated by the start winding. The result is the necessary torque (turning power) to start the motor. The size (capacity rating) of the start capacitor determines the amount of electrons discharged into The capacitor-start, induction-run motor is actually a split-phase motor with a special capac- itor that set off the phase in the start winding to increase starting torque. See Figure 25‑27. Start Capacitor The capacitor on the CSIR motor is a start capacitor. These are designed and used to create better starting torque than a run capacitor. A start capacitor usually appears as a black plastic cylinder with a hard cardboard top that houses the electrical push-on-type connections. See Figure 25‑28. The start capacitor is not as durable in construction as a run capacitor because it does not stay in the circuit during motor operation. It gets the motor started, then is disconnected along with the start winding. Typically, a start capacitor can withstand about 20 starts per hour before suffering internal damage. 1 3 Start Run N L1 Black wire White wire Overload Run terminal Start terminal Common terminal Run capacitor Permanent Split-Capacitor (PSC) Motor Goodheart-Willcox Publisher Figure 25‑26. Electrical connections for a hermetic compressor containing a PSC motor. Note the run capacitor is in series with the start winding. Start capacitor (in shell) Goodheart-Willcox Publisher Figure 25‑27. A CSIR motor uses a capacitor to shift the phase of the power (and thus magnetic field) in the start winding. As a result, the motor is better able to start under heavy load. Goodheart-Willcox Publisher Figure 25‑28. Start capacitors are available in various sizes, depending on motor requirements. They are less- durably constructed than run capacitors because start capacitors are used only briefly, whenever the motor is started. 500 Heating and Cooling Essentials Copyright Goodheart-Willcox Co., Inc.