MMF Harmonics Effect on the Embedded FE Analytical Computation of PM Motors

Abstract

This paper aims to define a minimum set of finite-element (FE) solutions to be used in the design and analysis of saturated permanent-magnet motors. The choice of the FE solutions belonging to this set is strictly associated with the classical <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> - <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> axis theory, and it is described in terms of key points on the flux-magnetomotive-force diagram. When synchronous machines are considered, such a diagram has a regular shape, so that a huge reduction in FE field solutions is possible with no loss of accuracy. It is also shown that the torque computed by using the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> - <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> axis theory is almost independent of the variation of the flux linkage with the rotor position. At last, this paper describes a technique in which few FE solutions allow the identification not only of the average torque but also of the main torque harmonics. As a result, the torque behavior versus rotor position can be rapidly predicted.