Common faults analysis of scroll compressor

When the compressor is in operation, a large amount of refrigerant gas is discharged and a small part of lubricating oil is carried away The short-term oil shortage of the compressor will cause abnormal wear of all relevant parts in the compressor, resulting in vibration and noise; the long-term oil shortage will cause overheating of all relevant parts in the compressor, resulting in bearing sintering, shaft holding, compressor built-in protection, exhaust or top temperature protection, overcurrent protection, power air switch tripping, abnormal operation sound of the compressor, excessive temperature in the compressor chamber, etc Cause: 1 The compressor starts and stops frequently for a long time 2 The system contains air or water 3 Dilute lubricating oil by system return or refrigerant migration 4 Reverse rotation of compressor (such as wrong phase sequence) 5 The leakage of system refrigerant makes the lubricating oil of compressor less 6 There are other chemicals in the system, which cause the lubricating oil to deteriorate after chemical reaction with the lubricating oil Liquid hammer of compressor When the compressor returns a large amount of liquid, the liquid drop will produce a great impact on the whirlpool during the compression process, which may break the whirlpool; the viscosity of the lubricating oil containing a large amount of liquid refrigerant is low, which can not form enough oil film on the friction surface, resulting in the rapid wear of the moving parts in the compressor; the refrigerant in the lubricating oil will boil when it is heated during the transportation process, which will affect the normal transportation of the lubricating oil After the liquid strike, the fragments of the scroll plate fall off the coil, damaging the insulation layer of the coil, and the current protection or the built-in protection of the compressor may not act Cause: too much refrigerant added, resulting in a large amount of liquid return from the system The internal fan does not rotate and the air volume is small, which leads to incomplete evaporation of refrigerant When the power is cut off, the EXV valve still keeps a certain degree of opening, resulting in a large amount of liquid return of the system Too much oil is added, resulting in system oil hammer (low pressure chamber compressor) Compressor high temperature burnout compressor high temperature overheating performance for exhaust or top temperature protection, compressor cavity temperature is too high, high pressure protection Long time high temperature and overheating will not only reduce the insulation performance and reliability of the motor, shorten the service life of the motor, but also reduce the lubricating ability of the lubricating oil, and even cause the carbonization and acidolysis of the lubricating oil After acid hydrolysis, the lubricating oil will cause copper plating After copper plating, the small metal chips generated by wear are mixed in the lubricating oil, which on the one hand weakens the lubricating effect of the lubricating oil; on the other hand, the small metal chips are gathered in the motor winding due to magnetism, forming a conductive circuit, leading to partial discharge or coil short circuit Cause: system vacuum is not enough Too little refrigerant addition or refrigerant leakage Ice blockage in the return pipe of the system causes high exhaust or top temperature If the connecting pipe is too long or the pipe diameter is small, the system resistance will increase, resulting in the increase of exhaust temperature and pressure The damage of compressor motor is mainly manifested in the damage of stator winding insulation layer (short circuit) and open circuit After the winding is burnt out, some phenomena or direct causes leading to burnout are covered up, which makes it difficult to analyze afterwards and investigate the causes The faults are: the contactor is frequently closed or burnt, the over-current protection or the compressor built-in protection, the power switch trips, the compressor chamber temperature is too high Cause: the contactor contact is burnt or abnormal, such as phase loss and phase deviation The rated voltage of the power supply shall not exceed ± 10% The unbalance rate of three-phase voltage shall not exceed 3% The load current under unbalanced voltage is 4-10 times of that under normal operation All the above reasons may cause the worn metal chips to damage the insulation layer of the coil and burn the motor Insufficient cooling of the motor, large leakage of refrigerant or low evaporation pressure will reduce the mass flow of the system, making the motor unable to get good cooling.