bimetallic metal strips, or by its expansion of the hot wire, depending on the design of the relay.
Essentially, an overload protector is a heat sensitive device much like a circuit breaker. When current in the circuit increases above normal, the added current heats a bimetallic strip that bends and opens a pair of contacts. The opening of the contacts disconnects the motor-running circuit and the motor stops. This prevents damage to the compressor motor when troubles occur, such as a defective starting relay, an open starting capacitor, or high-head pressure. Figure 14-38 shows a typical bimetallic disk-type overload protector. This overload protector is connected in the common line and mounted on the compressor motor shell.
In hermetic refrigeration and air-conditioning work, capacitors are
Figure 14-38. - Bimetal disk-type overload.
Figure 14-39. - Motor starting.
Start capacitors are connected in series with starting windings. By looking at figure 14-39, you can see the location of the start identified in two groups: start capacitors and run capacitors. These may be identified further as dry capacitors that are used for intermittent operations (start capacitors) and electrolytic capacitors that are used for continuous operation (run capacitors). capacitor in a circuit. Because a start capacitor is placed in series with one of the two stator windings, the current will lead, as compared to the current going directly to the connected stator winding. This, in turn raises the attraction of one stator winding over the other, allowing the motor to begin turning. Figure 14-39(A) shows that stator winding 2 is stronger than stator winding 1. Therefore, the motor begins to turn in the direction of the stronger attraction. Once the initial starting of the motor is completed, the start capacitor is removed from the circuit
Figure 14-39. - Various types of capacitors.
Run capacitors are connected in the circuit between the line side of the starting and running windings. This type of capacitor serves to provide a smoother and quieter operating motor.Continue Reading