Air conditioner motor load includes the load required to compress the gas and the load required to overcome mechanical friction. If the pressure ratio is too large, or the pressure difference is too large, the compression process will be more difficult; the increase of frictional resistance caused by the failure of lubrication, and the blocked rotor of the Air conditioner motor in extreme cases will greatly increase the motor load. Lubrication failure and increased frictional resistance are the primary reasons for abnormal load.

Overheating of the compressor will cause the lubricating oil to be thinned or even coked at high temperature, which will affect the formation of normal oil film. The oil return of the system is not good, and the compressor is short of oil, which naturally cannot maintain normal lubrication. The crankshaft rotates at a high speed, the connecting rod piston moves at a high speed, the friction surface without oil film protection will heat up rapidly, and the local high temperature will cause the lubricating oil to evaporate or coke rapidly, making the lubrication of this part more difficult, and causing local serious wear within a few seconds.

Small-power compressors (such as refrigerators, household air conditioner compressors) due to the small torque of the motor, often appear stalled (the motor cannot rotate) after the lubrication fails, and enter the dead cycle of "stall-thermal protection-stall", Air conditioner motor motor It's only a matter of time before it burns down. The high-power semi-hermetic compressor motor has a large torque, local wear will not cause stalling, and the motor power will increase with the load within a certain range, which will cause more serious wear and tear, and even cause cylinder bite (piston stuck in the cylinder inside), the connecting rod is broken and other serious damage. The current in the locked rotor (locked rotor current) is about 4-8 times of the normal running current.