Analytical and experimental analysis of Back EMF waveform of a TORUS-type non-slotted axial flux permanent magnet synchronous machine with shifted rotor

•A formula for calculating Back EMF waveform of the machine with shifted rotor.•An algorithm for mitigating a special harmonic component of Back EMF.•An analytical formula for determining the optimum value of rotor shifting angle.•Effectiveness of rotor shifting method on reducing the THD of Back EMF waveform. In this paper, the effectiveness of rotor shifting technique on the Total Harmonic Distortion (THD) reduction of back electromotive force (Back EMF) of a TORUS type non-slotted axial flux permanent magnet (TORUS NS-AFPM) machine is investigated. The paper’s objective is to conduct this investigation using analytical and experimental methods. Therefore, an analytical formula is proposed for obtaining Back EMF of the machine with shifted rotor. A 3.7 kW and 1400 rpm machine is selected as case study machine and the effectiveness of rotor shifting technique on the THD reduction of Back EMF is confirmed using the proposed formula and experimental results. In addition, an analytical technique for calculating the optimum value of rotor shifting angle for minimizing THD of Back EMF is proposed. The obtained results confirm that the THD of Back EMF of the case study machine decreases from 11.5% to 5% by optimal selection of rotor shifting angle.