7-3.Relay
Operating principle | Inspection method |
The relay momentarily energizes the start winding to start the rotation of the compressor motor.
Most later refrigerator models use a solid state type relay.
Unlike the mechanical type relay, the solid state relay has no coil and no moving contacts.
This relay consists of a small solid state wafer that has a low resistance at room temperature.
The wafer is positioned between electrical terminals that connect to the compressor terminals.
As voltage is initially applied to the compressor circuit, current flows through the run winding and, in parallel, through the relay and start winding . Initially , the resistance of the relay is low enough to pass sufficient current through the start winding and permit the compressor to start.
Then, instantaneously, the resistance of the relay goes
This type of relay is called a PTC(positive temperature coefficient) relay because the resistance goes high as the temperature increases.
The solid state relay can be tested for continuity, using an ohmmeter. The measured resistance of the relay, at room temperature, should be within 10% of the value stated on the schematic wiring diagram for the particular model.
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