A built-in bearing sensor to measure the shaft motion of a small rotary compressor for air conditioning

It is very difficult to measure the shaft motion of a small rotary compressor because of mounting space availability, exposure to high temperature and high pressure as well as electromagnetic noise from the motor. This paper details the development of a built-in bearing sensor to measure the shaft motion of a rolling piston type compressor for an air conditioner. The bearing sensor is calibrated indirectly through measuring the oil relative permittivity. The shaft motions in both transient and steady state conditions are measured successfully using this built in bearing sensor.