Comparison of Calculation Methods for Hybrid Stepping Motors

In scientific and industrial research and development, usually, one of two possible methods to predict a motor's performance is used. Analytical calculation based on the motor's electric and/or magnetic circuit provides results almost instantaneously but may be faulty when saturation effects have to be considered or complex geometries are involved. In this case, the finite-element method (FEM) is a useful and widely deployed tool-its disadvantage being that it is more time-consuming than analytical modeling. Most motor geometries can be simulated using a 2-D FEM analysis. However, for some motor geometries, the 2-D FEM analysis is not feasible, e.g., because of a 3-D distribution of the motor's electromagnetic field. One of those is the hybrid stepping motor (HSM). Analytical modeling of these motors proves to be difficult due to their complex geometry. This work presents an improved approach to calculating HSMs based on a combination of analytical and numerical methods. Compared with a 3-D FEM analysis, the combined model proves to be much faster. Measurements and results gained from 3-D FEM models of different sizes prove the method's validity. The models' results are similar; the analytical approach, however, has the advantage of a much shorter calculation time.