An analytical formula for selecting the feeding voltage and frequency in a TORUS-type nonslotted axial flux permanent magnet machine design

Abstract

Axial flux permanent magnet (AFPM) motors are usually controlled by drive; therefore, in the design of thesemachines the feeding voltage and frequency are completely independent parameters. Undoubtedly, the values of theseparameters have significant effects on the performance characteristics of the machine. The main objective of this paperis to investigate the effects of these parameters on the efficiency of a double-sided TORUS-type nonslotted (TORUSNS) AFPM motor and propose a formula for selecting the optimal values of the feeding voltage and frequency at thebeginning of the design process. To fulfill this goal, different machines with various speeds, powers, and feeding voltagesare designed based on a proposed design algorithm. Then a formula for calculating machine efficiency is presented basedon the frequency, number of pole pairs, output power, and feeding voltage of the machine. In order to confirm the validityof the proposed formula, several fabricated machines with different powers and speeds are selected as case studies. Theefficiency of these machines is calculated using the proposed formula and is measured in the laboratory. Comparing theresults confirms the excellent accuracy of the proposed formula.