A comparison of two finite element methods for determining flux density polarization in induction motor cores

This paper compares two forms of the finite element method (FEM) for the purpose of studying rotating magnetic flux in machine cores. The authors compare the use of a series of time-stepped magnetostatic solutions and a single time-harmonic formulation. The development of analysis tools for determining the amount of rotational flux and degree of flux density polarization in a machine core is of great importance to machine designers. A significant portion of the total core loss in an AC machine is caused by flux which rotates in the plane of the machine laminations. This rotating flux results in a polarized flux density at the roots of the stator teeth and all along the inner periphery of the stator core. The total iron loss in the material caused by rotating magnetic flux may be much larger than the iron loss due to alternating flux. A method of determining the amount of rotational flux will aid the designer in predicting no-load core loss and locating potential hot spots in the machine core