Samsung RL-28FBSI, Service Manual

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9
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
high-in effect, reducing the current flow through the
relay to a trickle . This trickle current causes the
resistance of the relay to remain high , thus keeping
the relay "open".
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.