[Objective] Fractional-slot concentrated winding (FSCW) dual-rotor motor

due to its unique winding distribution

generates abundant magnetomotive force harmonics in the air gap. During direct starting

the motor generates a large amount of inrush current and torque pulsation. To address this issue

this paper analyzes the electromagnetic torque characteristics under two starting methods-hard starting and soft starting-to evaluate whether these methods are conducive to the stable operation of the motor. Additionally

the validity of the virtual displacement method under these two starting conditions is verified. [Methods] This paper first introduced the basic structure and working principle of the FSCW axial dual-rotor motor. A mathematical model of the motor was then established based on winding theory. Based on simulation results

the transient and steady-state processes of hard and soft starting were analyzed

as well as the torque characteristics at different stator-rotor axial angles under both starting conditions. Next

the electromagnetic torque expression was derived based on the virtual displacement method. Finally

the electromagnetic torque under both starting conditions was discussed by combining the virtual displacement method and simulation results. [Results] Simulation data showed that during hard starting

the electromagnetic torque increased sharply

and the subsequent torque waveforms exhibited significant fluctuations and noticeable oscillations. Over time

the torque fluctuations gradually stabilized and reached a steady state

with the transient peak about twice the steady-state peak. Under both hard and soft starting conditions

the simulated electromagnetic torque was slightly lower than the result calculated by the virtual displacement method. The peak values and fluctuations of the simulation waveform showed significant variations when the stator-rotor axial angle was altered. [Conclusion] The results indicate that hard starting is not conducive to the stable operation of the motor. The stator-rotor axis angle affects both the magnitude of the electromagnetic torque and the torque pulsation. The simulated electromagnetic torque aligns well with the theoretical value

and the derived expression shows high accuracy

serving as a reference for subsequent calculations of the motor's electromagnetic torque.