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Analysis of Trouble
When motor windings have been burned or short-circuited between turns,
the fuse will be blown repeatedly, and the blowout occurs particularly at the
instant when you close the knife switch.
Remedy
Check the terminals and the outer casing to see whether they are
short-circuited, and measure the resistance of each phase with an avometer.
If short circuit occurs or the resistance of a certain phase is low, this means
that short circuit does exist in the windings and/or between turns, and
insulation layers have been burned or deteriorated. A megameter can be
used in this inspection, too. I f the insulation resistance is lower than 2 MΩ,
this means that the insulation layer is already breakdown. If the motor has
been burned, repair it or replaced it with a new one.
b) Fault of control relay
Analysis of Trouble
Overheat, burnout or wear of control relay contacts may occur generally.
All these will cause poor contact in electricity.
Remedy
Dismantle it to repair, or replace it with a new one.
c) Poor electric contactor in thermostat
Analysis of Trouble
Burnout of contactor and leakage of temperature sensing agent may occur
generally.
Remedy
Replace the old with a new one.
d) Check the terminals for loose connection and electric circuits for other
abnormal phenomena.
5) Mechanical faults of compressor
a) Seizing of shaft
This phenomenon is caused mostly by poor lubrication, such ad
insufficient quantity of lubricant, clogging in the lubricant oil line, or
intermittent lubricant oil supply. Dirt and other impurities in the lubricant oil will
increase its viscosity and cause the shaft to be seized. Copper plating may
also result in seizing of shaft.
b) Seizing of piston
This is caused by too small fit clearance between the piston and cylinder
or expansion due to heat.
Judgement of seizing shaft and piston: After the refrigerator has been
powered on, the compressor will not start and run, but a slight hum sound can
be heard, and several seconds later, thermal protective relay will actuate and
make the contacts open; this process will occur repeatedly, but the
compressor cannot be started.
Maintenance Service and Trouble Shooting
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