Refrigerator starting relay, starting Capacitor
and overload Protector.
motor employs both a start and run winding. The run winding
is energized during the complete cycle of operation, whereas
the start winding is energized only during the starting period.
The current-operated type of relay has a coil connected in
series with the run winding of the compressor. Some current-operated
relays plug directly onto the compressor while others do not.
Most relays are mounted in a case located on the compressor.
When the thermostat closes, the compressor attempts to start,
drawing heavy current through the run winding and the relay
coil. This strong current flow through the relay coil creates
a magnetic field strong enough to cause the start contacts
to lift and close, energizing the start winding. When the
compressor reaches approximately 3/4 running speed, the current
flow through the relay coil decreases (due to the countering
electrical magnetic field in the motor) and as the magnet
weakens, the start contacts fall open. This type of relay
must be used with an overload protector and must be mounted
in an upright position, so that the contacts can fall freely
to the "open" position.
bimetallic overload protector is mounted in series with
the motor windings. Should the current in the motor windings
increase to a dangerous value, the heat developed by the
passage of the current through the protector will cause
it to open. This breaks the circuit to the motor windings
and stops the motor before any damage can occur.
starting capacitor (when required) is momentarily placed
in series with the start winding to increase the starting
torque of the compressor. The starting capacitor drops out
of the circuit as soon as the start contacts fall to the
testing the capacitor, disconnect the power supply and place
the capacitor in a Capacitor Analyzer. If an analyzer is
not available, follow the procedure below.
testing the capacitor, disconnect the power supply and remove
all wiring to the capacitor. Discharge the capacitor using
a 20,000-ohm, 2-watt resistor, by placing the resistor across
the capacitor terminals. Set the ohmmeter on the highest
resistance scale and attach the leads to the capacitor terminals.
The needle should deflect instantly toward zero and return
slowly to infinity. This should occur each time the leads
are reversed. This indicates the capacitor is not shorted
or open. If the needle stays at or near zero or remains
on infinity, the capacitor is defective and should be replaced.
Be sure to reverse leads and check again before condemning
The information contained on these pages should never be
relied upon as a repair guide or be used to make repair
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