Estimation of radiation patterns from the stator winding of AC motors using array model

Abstract

To predict the radiated emission (RE) from AC motors in driver systems under the CISPR 25 standard, this paper proposes a method to estimate the radiation pattern of the stator winding by using antenna array theory. The availability of applying the proposed method is ensured by identifying the radiation region boundaries of the winding structure of a reference motor. The array model of the stator winding can be constructed by magnetic vector potentials from the circular array of axial and end-winding current elements. The calculated patterns, which are excited by the balanced three-phase harmonics at the resonance frequency, show that the radiation becomes significant when the harmonic number is not a multiple of three. Also, we can find that the radiation from the end-winding currents is dominant. Since the estimated radiation patterns are fairly correlated with 3D full-wave simulation results, the proposed method is expected to be used for the prediction of the RE from any stator winding configuration.