Utilising the Core Capacitance Achieved Through Ultra-Thin Soft Magnetic Sheets and Insulators

Wide-bandgap semiconductors are employed for improved power density by leveraging their superior switching frequency capabilities. Nevertheless, the introduction of switching harmonics results in increased losses on both the drive and machine sides. Slotless permanent magnet (PM) machines are most susceptible to this issue due to their inherent low inductance. Therefore, it is necessary to implement a filtering mechanism to remove these high-order harmonics from the phase currents. This paper presents a novel integrated filter scheme that utilises the interlaminar core capacitance. The stator is fabricated through the process of creating spiral laminated sheet with a thin layer of insulation film. Thin nature of the recent state-of art magnetic sheets helps to get capacitance values in the $\mu F$ range. Various capacitor orientations are proposed for different filtering topologies. Furthermore, the obtainment of available capacitance values is accomplished through the utilisation of sizing equations that have been derived specifically for slotless permanent magnet machines, ranged from 400 W to ${200}\ kW$. A capacitance of ${0.25}\ \mu F/kW$ is obtained with ${3}\ \mu m$ Mylar film and ${20}\ \mu m$ soft magnetic sheet for 2 pole slotless machines with ${100}\ m/s$ rotor tip speed. The magnitude of this parameter is correlated by the number of poles $(\propto 1/p)$ and the linear velocity of the rotor $(\propto 1/v)$, and it is subject to thorough and comprehensive analysis. The objective of the survey is to demonstrate the potential benefits, and challenges of employing the core capacitance acquired through the proposed strategy.