Investigation of Noise Sources in Fractional-Slot Concentrated Winding Motors Considering High-Order Radial/Tangential Electromagnetic Force Combination and Modulation

Traditional methods equate the slotted stator as an unslotted model and employ an approximation where the stator deformations are considered inversely proportional to the fourth power of the order of air-gap electromagnetic force density (AEFD). This approach effectively overlooks the contributions of high-order forces. Furthermore, it overlooks the influence of tangential forces, as radial forces typically have significantly greater amplitudes than tangential. However, the effectiveness of this method has been questioned. This study aims to establish a novel method for accurately identifying the harmonic components of AEFD responsible for vibration noise by investigating the electromagnetic vibration noise source in a 9-slot/6-pole fractional-slot concentrated-winding interior permanent magnet synchronous machine (FSCW-IPMSM). Initially, the modulation law of high-order force waves is investigated through a force conversion model, revealing the mechanism behind the strong modulation effect of high-order force waves. Subsequently, a quantitative analysis modulation force model is proposed. Building on this foundation, a multi-physics field coupling simulation method is employed to predict the electromagnetic vibration noise influence mechanism of high-order radial and tangential AEFD, as well as their coupling effects. The results demonstrate that the vibration noise at the frequency of $18f_{e}$ in this motor is primarily induced by the coupling effects of high-order radial and tangential AEFD components. Neglecting the contribution of tangential AEFD significantly underestimates the actual vibration levels in the motor. The research outcomes emphasize the importance of considering tangential AEFD and high-order force modulation effects, providing a fresh perspective for accurately predicting the electromagnetic vibration sources in FSCW-IPMSM.