Air compressor motor burned Case Analysis - Abnormal load and stall

Air compressor motor  load including compressed gas required to load and load needed to overcome mechanical friction. Compression ratio is too large, or the pressure is too great, the compression process will be more difficult; and friction lubrication failure caused by increased and motor stall in extreme cases, will greatly increase the electrical load.

Lubrication failure, friction increases, is the leading cause of abnormal loads. Back diluted lubricating oil, lubricating oil overheating, lubricating oil coking deterioration, and starvation, and this will disrupt the normal lubrication, cause lubrication failure. Back diluted oil, affect the formation of normal friction surface oil film, even washed away the original film to increase the friction and wear. Compressor overheating can cause thinning or lubricating oil temperature coking, affect the formation of normal oil film. System back to the oil well, compressor oil, natural unable to maintain normal lubrication. High-speed rotation of the crankshaft, connecting rod and piston speed movement, no friction surface protection film will quickly heat up, local temperature rapid evaporation of the lubricant or coking, making it more difficult to lubricate the parts, which can cause severe localized wear within a few seconds.

Lubrication failure, partial wear, the need for greater torque rotating the crankshaft. Low-power compressors (such as refrigerators, home air conditioning compressor) due to the small motor torque, often stall after lubrication failure (motor can not rotate) phenomenon, and enter the "stall - thermal protection - stall" dead loop, motor burn only time. The high-power semi-hermetic compressors motor torque is large, local wear will not cause stall, motor power will be in a certain range with the load increases, causing more serious wear and tear, and even cause seizures (live Fonseca in the cylinder inside), rod fracture and other serious damage.

Current stall time (Stall current) is about 4-8 times the normal running current. Motor starts the instant, peak current accessibility or reach stall current. Since the resistance of heat proportional to the square of the current release, start and stall when winding current will rapidly warming. Thermal protection can be protected in the event stall electrodes, but generally do not have fast response, can not prevent frequent start winding temperature change caused. Frequent starts and abnormal load, the winding withstand high temperature test, will reduce the insulation performance of enameled wire.

In addition, the compressed gas will be needed to load with the compression ratio increases and the pressure increases. Therefore, high-temperature compressor for low temperature, or cryogenic compressors for high temperature, will affect the electrical load and heat, is not appropriate, will shorten the electrode life.

After winding insulation deterioration, if there are other factors (such as metal shavings, a conductor circuit, acidic lubricants, etc.) with, it is easy to cause a short circuit and damage.