Finite Element Analysis of Electric Machines: Post-Processing Methods

Abstract

As the finite element method finds more applications for the analysis and design of electric machines, it is becoming increasingly important to employ post-processing methods that derive the most accurate and reliable results from the vector potential solution. In this paper, different methods for determining flux and flux linkage, force and torque, and inductance are compared. Improved methods are proposed to save computing time and to increase accuracy. The improved Maxwell's stress tensor torque (or force) post-processing is insensitive to local errors in the finite element solution. The improved co-energy torque (or force) calculating method increases accuracy and reduces computing time by using the direct derivative of co-energy instead of the co-energy difference between two solutions. The improved inductance calculation eliminates the need for specially designed finite element solutions. These refined post-processing techniques are demonstrated by applications to a linear induction motor and to a rotary permanent magnet synchronous machine.