Determination of air gap permeances of hybrid stepping motors for calculation of motor behaviour

Prediction of hybrid stepping motor performance is made possible using an analytical model based on the motor´s equivalent magnetic circuit. The motor´s static torque behaviour can be determined by drawing the energy balance of the magnetic circuit. Circuit elements consist of magnetomotive forces induced by the permanent magnet and the stator´s windings as well as permeances for iron parts and air gap. These permeances have to be identified with great care in order to calculate the motor correctly. The magnetic circuit is described, as is the calculation of the motor´s torque behaviour. Two ways of determining permeances are outlined and discussed. These include two-dimensional finite element analysis as well as a flux tube approach.