Design and Analysis of Variable-Reluctance Stepping Motor as Actuator Element of New Type Automatic Transfer Switch

Abstract

The method of designing a single-stack variable-reluctance (VR) stepping motor for use as an actuator of the transition mechanism of the new type of automatic transfer switch is presented in this paper. The design procedure is explained and supported with several equations derived from electromechanical conversion theory. The golden ratio is introduced in design equation which relates the axial length of the stator core to the stator bore diameter. The flux density inside all parts of the machine is investigated using finite-element analysis based software package MagNet Infolytica in order to ensure the machine is operated at linear region of the core magnetization curve. The software also generates the torque profile which graphically figures the electromagnetic torque produced by the machine versus the rotor position. The material for stator and rotor cores uses high permeability magnetic material such as Carpenter silicon steel. The stepping motor will have 6 poles at the stator and 4 teeth at the rotor and will produce maximum torque of 0.3 Nm at 1 A excitation current. Based on the simulation results, the dimensions of the stator and rotor cores of VR stepping motor are as follows, motor axial length 80 mm, stator outer diameter 122 mm, stator bore diameter 72 mm, rotor outer diameter 71 mm and rotor shaft diameter 20 mm, and also the coil of each stator poles will have 800 turns.