Stray Electromagnetic Field Distribution around Permanent Magnet Synchronous Motor Drive

Abstract

The low frequency electromagnetic emission from permanent magnet synchronous motors is studied. The main objective is to provide safety regions for humans in the vicinity of these motors, especially that, these motors are now being used widely in humans' existence areas, where high flux densities are expected. In this study, a new equivalent magnetic circuit is proposed to estimate the stray fields at the surface of the motor. The analysis shows that the emission of the stray field in the radial directions depends on the permeability of the stator structure. Low values of the permeability may result in very high stray flux emissions at level that shielding may be required to protect people in the surrounding. Relatively far away from the stator (e.g, 50 cm for the tested motor), normally the flux is of low level and may not represent an exposure threat. It's imperative that, the measurement waveforms of the magnetic field show that waveforms similar to the heart beat may result, which constitutes threat for pacemaker holding people. In addition, the measurement waveform of the x-sensor (radial component) provides important information that can be used for the rotor position estimation.