LG LRFD21855ST Service Manual Download

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4-1 COMPRESSOR

4-1-1 Role

The compressor intakes low temperature and low pressure
gas from the evaporator of the refrigerator and compresses
this gas to high-temperature and high-pressure gas. It then
delivers the gas to the condenser.

4-1-2 Composition
The compressor includes overload protection. The PTC
starter and OLP (overload protector) are attached to the
outside of the compressor. Since the compressor is
manufactured to tolerances of 1 micron and is hermetically
sealed in a dust and moisture-free environment, use
extreme caution when repairing it.

4-1-3 Note for Usage
(1) Be careful not to allow over-voltage and over-current.
(2) If compressor is dropped or handled carelessly, poor

operation and noise may result.

(3) Use proper electric components appropriate to the

Particular Compressor in your product.

(4) Keep Compressor dry.

If the Compressor gets wet (in the rain or a damp
environment) and rust forms in the pin of the Hermetic
Terminal, poor operation and contact may result.

(5) When replacing the Compressor, be careful that dust,

humidity, and soldering flux don’t contaminate the inside
of the compressor. Contamination in the cylinder may
cause noise, improper operation or even cause it to
lock up.

4-2 PTC-STARTER

4-2-1 Composition of PTC-Starter
(1) PTC (Positive Temperature Coefficient) is a no-contact

semiconductor starting device which uses ceramic
material consisting of BaTiO

(2) The higher the temperature is, the higher the resistance

value. These features are used as a starting device for
the Motor.

4-2-2 Role of PTC-Starter
(1) The PTC is attached to the Sealed Compressor and is

used for starting the Motor.

(2) The compressor is a single-phase induction motor.

Durign the starting operation, the PTC allows current
flow to both the start winding and main winding.

4-2-3 PTC-Applied Circuit Diagram

●

Starting Method for the Motor

4-2-4 Motor Restarting and PTC Cooling
(1) It requires approximately 5 minutes for the pressure to

equalize before the compressor can restart.

(2) The PTC device generates heat during operation.

Therefore, it must be allowed to cool before the
compressor can restart.

4-2-5 Relation of PTC-Starter and OLP
(1) If the compressor attempts to restart before the PTC

device is cooled, the PTC device will allow current to
flow only to the main winding.

(2) The OLP will open because of the over current

condition. This same process will continue (3 to 5
times) when the compressor attempts to restart until
the PTC device has cooled. The correct OLP must be
properly attached to prevent damage to the
compressor.
Parts may appear physically identical but could have
different electrical ratings. Replace parts by part
number and model number. Using an incorrect part
could result in damage to the product, fire, injury, or
possibly death.

4-2-6 Note for Using the PTC-Starter
(1) Be careful not to allow over-voltage and over-current.
(2) Do not drop or handle carelessly.
(3) Keep away from any liquid.

If liquid such as oil or water enters the PTC,
PTC materials may fail due to breakdown of their
insulating capabilities.

(4) If the exterior of the PTC is damaged, the resistance

value may be altered. This can cause damage to the
compressor and result in a no-start or hard-to-start
condition.

(5) Always use the PTC designed for the compressor and

make sure it is properly attached to the compressor.
Parts may appear physically identical but could have
different electrical ratings. Replace parts by part
number and model number. Using an incorrect part
could result in damage to the product, fire, injury, or
possibly death.

4. ADJUSTMENT

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PTC STARTER

SEALED

TERMINAL

COMPRESSOR
MOTOR

PTC

OVERLOAD PROTECTOR

Resistance Starter Capacitor Running

Figure 18