Direct motor rotor pyrometry using mid-infrared hollow waveguide

A remote pyrometry method was applied to an interior permanent magnet synchronous motor (IPMSM) for a direct measurement of its rotor component temperatures. An accurate means of permanent magnet (PM) thermometry is a critical factor in an IPMSM design and operation since excessive heat can lead to irreversible performance degradation of the motor. A hollow waveguide (HWG) mounted inside the motor housing, just above the rotor end surface, collected mid-infrared surface emissions from exposed PMs and rotor core sections during rotation. The signal was then analyzed to resolve temperatures across small rotation angles along the trajectory traced out by the HWG. The sensor was calibrated in laboratory conditions and demonstrated on an actual motor under various operating conditions. The sensor enabled direct temperature measurements to within +/- 3 degrees C uncertainty near room temperature with +/- 1 degrees angular resolution at 4500 RPM. The uncertainty decreased to less than +/- 1 degrees C above 100 degrees C.