Overview of the Optimal Design of the Electrically Excited Doubly Salient Variable Reluctance Machine

The Electrically Excited Doubly Salient Variable Reluctance Machine (EEDSVRM) is a new type of brushless machine designed according to the principle of air gap reluctance change. There is neither permanent magnet steel nor excitation winding on the rotor. The rotor is made of silicon steel sheets, thus the structure of the variable reluctance machine is very simple. There are many optimization methods for this type of machine optimal design, such as novel machine topology optimization, finite element simulation-based optimization, mathematical analysis-based optimization, intelligent algorithm-based optimization, and multiple fusion-based optimization. Firstly, this article introduces the basic structure and working principle of the EEDSVRM and analyzes both its common regularity and individual difference. Then, the different optimization design methods of EEDSVRM are reviewed, the advantages and disadvantages of the different optimization methods are summarized, and the research interests of the optimization design of variable reluctance machines in the future are prospected.

Electromagnetic Torque Improvement of Doubly Salient Permanent Magnet Machine Using Pole Ratio Adjustment Technique

This paper introduces the pole ratio adjustment technique to improve the torque characteristics of the doubly salient permanent magnetic machine (DSPM). The electrical characteristics of the machine, namely the magnetic field distribution, flux linkage, back-electromotive force (EMF), and cogging torque, were obtained under open-circuit conditions. The electromagnetic torque and ripple torque were examined under the loaded condition. The simulations, based on the 2D-finite element method, show that the optimal pole ratio for the DSPM structure is with 18 stator teeth and 15 rotor poles. This optimal structure achieves a larger phase back-EMF than the conventional structure, as well as had a better magnetic flux path with a reasonable cogging torque. The on-load test also confirmes that the proposed optimal structure can produce a significantly higher electromagnetic torque than the conventional machine while maintaining a satisfactory torque ripple. Furthermore, an experimental prototype of the DSPM structure having 18/15 stator/rotor poles was fabricated and tested to verify the simulations. The experimental results were in good agreement with the simulations. The design technique and the fabricated prototype demonstrate the DSPM utilization for low-speed/high torque applications.