Relays are a necessary part of many control and experimental light chains. They are similar in design contactors, but it is generally easier in construction, so they are less current.
Compressors used for household refrigerators, freezers, dehumidifiers, machines, and water coolers have capacitor-start, induction-run type of engine. This type of compressor can have a chain similar to figure 14-2. When the compressor is on the thermostat, requiring action, the relay is closed and the start winding in the chain. As soon as the engine comes to 75 percent of the nominal speed is a lack of current through the coil of the relay get his energy, and it pulls the relay contacts open, thus accepting the start capacitor and start winding of the circuit. This allows the engine to work with one winding it was intended.
Fig. 14-3 shows the current type of relay. This method is typically used for small-scale refrigeration compressors to 3/4 PS Fig.
14-4 shows the potential relay type. This is usually used with large commercial air compressors up to 5 HPC.
Protection of the motor against a sustained overload is carried out by limiting the time overload relay. They are applicable during the start-up period and during the time of passage. Relay deferred long enough to take care of the heavy momentary inrush currents and overloads without tripping...