Model representation of claw-pole stepping motors

The performance of claw-pole stepping motors is significantly influenced by stator iron losses due to the flux-carrying nonlaminated construction. To obtain a suitable model of the magnetic circuit, the stator iron is modeled as a conducting slab of simple geometry; the analytical solution of the skin problem can be approximated by a half-order transfer function. The magnetic circuit consists of the conducting slab in series with the air gap; its dual electric circuit is a complex main field inductance, with its inductive and resistive components depending on frequency. This allows one to use a revised version of the conventional synchronous machine model circuit, the parameters of which are determined from tests. The model is used to simulate steady-state operation of the stepping motor when fed by symmetrical currents. Examples are presented of constant current and constant voltage operation. Attention is drawn to the torque curve in continuous operation. Simulations are shown of the current waveforms when the motor is supplied by rectangular voltage. The results are in acceptable agreement with measured values.