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Analysis Of Common Faults In The Motor Of Compressor Refrigerator
- Jul 06, 2018 -

Most of the refrigerators of various refrigerators are totally enclosed, that is, both the compressor and the motor are sealed in the same steel shell. The power of the split phase single-phase induction motor is small, about 65w-120w. The general split phase single-phase induction motor has a high speed of 3000 turns per minute. In the stator coil of this kind of motor, apart from having a set of coarse winding running windings, a set of starting winding with a relatively fine diameter is also specially designed. The working winding and the starting winding work together to produce larger starting torque, and the rotor of the motor runs and rotates. Because the line diameter of the starting winding of the motor is very thin, the resistance value is larger, the temperature rise is correspondingly higher, and the motor is easily destroyed if the motor is in the starting state for a long time, so when the motor starts to start a few seconds, the starting relay will cut off the starting winding automatically.

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Because of the above particularity of this kind of motor, and also sealed in the compressor steel shell, the motor speed is high, so once the power supply voltage is unstable or the mechanical failure is produced, it will cause the fault of the motor heating temperature rise too high. The common faults are mainly the wear of the spindle bearing sleeve of the motor, the high temperature rise of the motor, the lack of lubricating oil in the compressor to make the motor heating, the long time overloading of the motor and the leakage of the electric motor.

1. Motor spindle wear

As the motor and compressor are sealed together, the lower part of the rotor center shaft of the motor is the oil suction tube, the upper end is the crankshaft of the compressor (for the reciprocating compressor). When the motor rotor is running with the central axis, only one copper bearing sleeve is supported, and the gap between the rotor and the stator is only about 0.3mm. Once the bearing sleeve is worn, the loosening between the shaft and the hole causes the eccentric swing of the motor rotor in operation, and the friction resistance increases, resulting in the rapid increase of the motor current. Add, heat the winding and burn out the motor. After this kind of fault is disassembled, the wear of the shaft sleeve of the motor should be carefully checked. When the diameter of the bore of the bearing is found to be more than 0.1mm, the bearing should be replaced in time.

2. Motor temperature rise serious

During the actual maintenance process, it is found that the temperature of the outer casing of the compressor is too high, which can be generally analyzed from the following aspects.

One is the deterioration of the refrigerating oil in the steel shell, thereby increasing the wear between the parts of the compressor. Compressor lubricating oil (i.e. refrigerant oil) is a very clear and transparent liquid. It is a special type of oil which is suitable for the environment with high temperature and low temperature. Once the oil is deteriorated, cloudy and sticky, it will aggravate the mechanical wear and oil blocking of the compressor, causing the motor to rise substantially and burn the motor.

The second is the lack of lubricating oil in the body of the compressor, which makes the moving parts of the compressor lack of oil supply, aggravates the friction between the metal surfaces of the components, causing the motor load to increase, the winding heating and the increase of temperature rise.

The third is that the internal winding of the motor is short circuited. If the compressor is running for a long time over a long time, the motor is subjected to the change of cold and hot temperature difference in the shell or the frequent start and stop of the compressor, which will cause the insulation aging short and heat of the motor winding. Check whether the motor has short circuit, and can measure the resistance value of each winding to judge. The resistance value of the general motor starting winding is about 23 Omega when no short circuit is short circuited, and the resistance value is about 11 Omega when the operating windings are not short circuited, and the value of the starting and running windings is about 35 Omega. If the motor winding is short circuited, its resistance value is much smaller than the normal value.

If there is a jam in the capillary of the refrigerator, the filter or some parts of the pipeline, the suction pressure of the compressor will be reduced or the exhaust pressure will be increased, which will aggravate the operating load of the compressor and cause the temperature of the motor to rise seriously. 

3. Leakage fault of motor

The leakage of electricity in the compressor housing can cause the whole refrigerator to be electrified, causing serious danger to the safety. Analysis of the main causes of motor leakage, mainly electrical wire insulation aging rupture, resulting in bare wire and steel shell touching electric conduction. Secondly, the serious leakage of the motor caused the motor to leak. Of course, it is possible to disassemble the compressor after maintenance, due to poor assembly or poor quality of insulated conductors, resulting in a loss of electrical insulation performance for a short period of time, resulting in a leakage of electricity.

In view of the above situation, when detecting whether the motor is leaks, the three lead wires of the motor can be used to judge the insulation value of the shell using the megaohm rocking meter. If there is no special Mega meter on hand, it can be detected by incandescent lamp. The specific detection method is to remove the three leading out lines of the motor from the junction column, connect the fire line in the power line to a certain lead line of the motor (each test one at a time), and then string the incandescent bulb in string between the chassis and the grounding wire, when the power line touches the induction line of the motor (the starting line, the running line). When starting the operation connection, the bulb lights up, indicating that the motor is leaking. It should be explained that the whole refrigerator leakage, not necessarily the electric leakage caused by the compression motor, such as the circuit system of the refrigerator, the thermostat, the relay, the lighting system and so on, can cause the leakage. Only after removing the above fault, can we check the electric leakage of the compression motor and confirm the leakage fault of the motor one day, only saw the saw open The compressor housing is taken out of the motor for repair or replacement.