LG LFX25976ST, Service Manual

Page: 19 / 82

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Multi-tester
4-2-4 Compressor problems diagnosis
When there is a problem or failure with the `operation,
you are kindly recommended to check it as follows ;
Measure the resistance between poles of the hermetic
terminal (as shown picture) with a multi-tester.
(measurement several minutes after power off)
Normal resistance range (measured at ambient
temperature 23
℃
)
Case 1-1
If the measured values lie in the normal resistance range as
in the table below,
Compressor is normal.
Case 1-2
If the measured values are above several M
Ω
or a infinity,
Wire is disconnected in the shell.
Case 1-3
If the measured values are excessively of small number,
There is short somewhere in the shell.
1) Check to normality by measurement of resistance
According to ambient temperature or operation situation,
the values could show a little deviation.
4-2-3 Compressor protection logic
Since linear Comp conducts linear reciprocating motion,
we have protection logic for compressor, motor and PCB
as the below.
- Stroke Trip
During the operation, if stroke is above the target value,
decrease the target volt by 3V.
- Current Trip
Current trip is set in order to protect compressor
mechanical part and drive from the overcurrent that might
arise during the operation.
Check the current for every 416.7us and if the Trip
exceeds 1.86Arms more than three times at Comp ON,
forcibly stop and restart six minutes later.
- Lock Piston Trip
If stroke is under 5mm even if the current is more than
14Arms, Take it as ‘piston lock’ and restart after 2’30” of
Comp OFF. Check the current and stroke for every
416.7us and if the condition fits more than three times at
Comp ON, the Trip occurs.
- IPM fault Trip
It occurs if FO signal received from IPM is LOW. For
every 416.7us, check whether FO signal is LOW. The trip
occurs if it is found three times during the five
periods(83ms).
P : Power Line
C : Common Line
Resistance
6~8
Ω
FC75LANE