1. Causing abnormal load or stalling
Excessive pressure ratio or pressure difference can make the compression process more difficult; The increase in frictional resistance caused by lubrication failure, as well as the extreme situation of motor stalling, will greatly increase the motor load. If the load increases to the point of thermal protection action, and the protection is automatically reset, it will enter a dead cycle of "locked rotor thermal protection locked rotor", frequent starting and abnormal loads will subject the winding to high temperature tests, which will reduce the insulation performance of the enameled wire. After the insulation performance of the winding deteriorates, if other factors (such as metal shavings forming a conductive circuit, acidic lubricating oil, etc.) cooperate, it is easy to cause a short circuit and damage.
2. Short circuit of winding caused by metal shavings
The sources of metal shavings include copper pipe shavings left during construction, welding slag, internal wear of compressors, and metal shavings falling off when components are damaged. During work, under the influence of airflow, these metal shavings or fragments will fall onto the winding. The normal vibration during the operation of the compressor, as well as the twisting of the winding due to electromagnetic force during each start-up, will promote the relative motion and friction between the metal shavings mixed between the windings and the enameled wires of the windings. Sharp metal shavings can scratch the insulation layer of the enameled wire, causing a short circuit and resulting in motor burnout.
3. Power shortage and abnormal voltage
The voltage variation range of the power supply cannot exceed ± 10% of the rated voltage. The voltage imbalance between the three phases cannot exceed 2%. If a phase loss occurs while the compressor is running, it will continue to operate but there will be a large load current. The motor winding will quickly overheat, and under normal circumstances, the compressor will be thermally protected. When the motor winding cools to the set temperature, the contactor will close, but the compressor cannot start, resulting in stalling and entering a "stalling thermal protection stalling" dead cycle. If a phase loss occurs during compressor start-up, the compressor will not start and will experience stalling, entering a dead cycle of "stalling thermal protection stalling".
5. Insufficient cooling of compressor motor
When a large amount of refrigerant leaks or the evaporation pressure is low, it will cause a decrease in the system mass flow, making it difficult for the motor to receive good cooling, and frequent protection will occur after the motor overheats.
6. Compressor liquid hammer damage
When the compressor returns a large amount of liquid, the droplets during the compression process will exert a great impact on the scroll, which may break the scroll; Lubricating oil containing a large amount of liquid refrigerant has low viscosity and cannot form sufficient oil film on the friction surface, resulting in rapid wear of moving parts inside the compressor; In addition, the refrigerant in the lubricating oil will boil when heated during transportation, which affects the normal transportation of the lubricating oil.
The debris of the vortex disk after liquid impact falls onto the coil, damaging the insulation layer of the coil, which may result in current protection or built-in protection of the compressor. The compressor can operate, but there is no exhaust, no high pressure, low current, and abnormal sound. Abnormal sound during compressor operation or compressor shaft jamming may cause current protection or air circuit breaker tripping upon startup.
7. Return of liquid causes damage to the compressor
Returning liquid can easily cause liquid hammer accidents. Even if it does not cause liquid impact, the return fluid of the high-pressure chamber structure will dilute or wash away the lubricating oil on the sliding surface, exacerbating wear. The return fluid of the low-pressure chamber structure will dilute the lubricating oil in the oil pool. Lubricating oil containing a large amount of liquid refrigerant has low viscosity and cannot form sufficient oil film on the friction surface, resulting in rapid wear of moving parts. In addition, the refrigerant in the lubricating oil will boil when heated during transportation, which affects the normal transportation of the lubricating oil. If the bearings on the motor end are severely worn, the crankshaft may settle to one side, which can easily lead to stator sweeping and motor burnout.
8. Excessive lubricating oil causes damage to the compressor due to hydraulic shock:
For low-pressure chamber compressors, high-speed rotating components such as rotors frequently collide with the oil surface. If the oil level is too high, it can cause a large amount of lubricating oil to splash. Once splashed lubricating oil enters the intake duct and is carried into the cylinder, it may cause liquid hammer.
9. Compressor damaged due to high temperature
Overheating phenomena such as high temperature of the motor, high exhaust temperature, and burnt lubricating oil are caused by problems such as excessive use, abnormal power supply, motor overload, refrigerant leakage, and high condensation pressure. The surface temperature of the compressor is one of the important indicators to determine whether the compressor is overheated. If the surface temperature exceeds 125 ℃, it is generally considered that the compressor is in a severely overheated state; If the surface temperature is below 100 ℃, the compressor temperature is normal.
10. Compressor motor damaged
The damage to the motor mainly manifests as the insulation layer of the stator winding being damaged (short circuit) and open circuit, etc. After the winding is burned, some phenomena or direct causes that led to the burning are covered up, making it difficult to analyze and investigate the cause afterwards.
Fault manifestations: frequent closing or burning of the contactor, overcurrent protection or built-in protection of the compressor, power switch tripping, high temperature in the compressor chamber, etc.
