Analysis on Torque Ripple Harmonics of BLDC Motor under Open Circuit Fault Conditions

The advancement of large-capacity batteries and electric propulsion systems has led to the adoption of electric propulsion systems in marine vessels. In applications such as military submarines, an increase in noise caused by failures in the electric propulsion system can compromise stealth capabilities. Motor noises are induced by torque ripple components. Thus, reducing torque ripple under fault conditions is a critical factor for ensuring stealth. This paper proposes a control method to mitigate multiple orders of torque harmonics in a multiphase brushless DC motor under a single-phase open-circuit fault. The method controls the magnitude and phase angle of the healthy phase currents while excluding the fault phase. The torque ripple caused by the single-phase open fault is identified through harmonic analysis, and compensation is achieved by adjusting the healthy phase currents' magnitude and phase angle. The proposed method was verified using PLECS and hardware-in-the-loop simulations.