with each other. Such a connection permits each capacitor to act independently and perform its duty to the start winding. At start-up, both capac- itors are energized. When the relay switch opens, only the start capacitor is disconnected. The circuit for the run capacitor is still available to control the phase of the current going through the start winding. 25.4 Capacitors A capacitor is an electrical device that can store an electrical charge. It can be used to improve the operating characteristics of single-phase induction motors by changing the phase of the electrical signal, which affects the magnetic field 25.3.5 Capacitor-Start, Capacitor-Run Motor The capacitor-start, capacitor-run (CSCR) motor runs as a CSIR during start-up and as a PSC for the rest of normal operation. It is another improvement on the split-phase motor. The most powerful of the single-phase induction motors, it provides both high starting torque and high running torque. The CSCR motor is used when the motor must start under a heavy load and carry a heavy load during the run cycle. The motor is typically used in small commercial systems with a thermostatic expansion valve. The CSCR motor is essentially a split-phase motor that combines the operating principles of the PSC and CSIR motors, using both start and run capacitors. At start-up, it operates as a CSIR motor because of the start capacitor. After start-up, a relay switch disconnects the start capacitor. The run capacitor remains in the circuit and keeps the start winding energized. The motor continues to run as a PSC. Hermetic CSCR Electrical Connections One leg of the power supply (white wire) is connected to the overload at Terminal 1. See Figure 25‑31. A wire from Terminal 3 of the over- load is connected to the common terminal. The other leg of the power supply (black wire) is connected to the relay, which branches through the capacitors to the start terminal or to the run terminal through the relay’s coil. Overall, the run and start windings are connected in parallel, and the overload is in series with common (so both windings). Connections from the relay and capacitors to the start winding are critical but really quite simple. First, connect the start capacitor in series with the relay switch and start terminal by connecting a wire from the relay switch terminal to one side of the start capacitor. Another wire is connected from the other side of the start capacitor to the start terminal. These connections are exactly like those on the CSIR motor. The run capacitor is connected to provide another circuit for the electrons to reach the start winding. This circuit must bypass the switch and start capacitor. The connections are called series- parallel because each capacitor is in series with the start winding but the capacitors are in parallel N L1 Black wire White wire Overload Relay coil C S R Run capacitor Start capacitor Switch Current relay 1 3 Capacitor-Start, Capacitor-Run (CSCR) Motor Goodheart-Willcox Publisher Figure 25‑31. Electrical connections for a hermetic compressor with a CSCR motor. The start winding, start capacitor, and relay switch are in series. The run capacitor is wired in parallel with the start capacitor and relay switch. 502 Heating and Cooling Essentials Copyright Goodheart-Willcox Co., Inc.