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21
4) Motor troubles and other electric faults
a) Motor windings have been burned or short-circuited between turns 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 ohmmeter. 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 multimeter can be used in this inspection,
too. I f the insulation resistance is lower than 2 M
a) Motor windings have been burned or short-circuited between turns 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 ohmmeter. 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 multimeter can be used in this inspection,
too. I f the insulation resistance is lower than 2 M
, 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 as 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.
E. Compressor won't stop
Sometimes, the compressor will run continuously (for several hours or run without end), If the food
placed in the refrigerator is not too much, there may be the following two situations: i) the refrigerator
very low, this means that the control system is probably out of order; ii) the control system works
normally, and there are troubles in the refrigerating system or other parts.
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 as 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.
E. Compressor won't stop
Sometimes, the compressor will run continuously (for several hours or run without end), If the food
placed in the refrigerator is not too much, there may be the following two situations: i) the refrigerator
very low, this means that the control system is probably out of order; ii) the control system works
normally, and there are troubles in the refrigerating system or other parts.
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