Frequency-Dependent Design of Coated Rotor Structures for Solid Rotor Induction Motors

Solid rotor induction machines (SRIMs) offer superior mechanical robustness and thermal durability, making them attractive for high-speed applications. However, their electromagnetic performance is inherently limited. This study investigates the impact of rotor coating on the performance of a 4 kW, 400 V, 400 Hz SRIM to overcome these limitations. A comprehensive parametric analysis is conducted using time-stepping 2D transient finite element simulations, considering different coating materials and thicknesses over a wide operating speed range. The coated rotor structure is systematically compared with the conventional smooth rotor design. The results demonstrate that rotor coating significantly improves key performance metrics, including efficiency, power factor, and electromagnetic torque, while effectively reducing rotor losses and mitigating space harmonic effects. The radial component of the air-gap flux density is analyzed to reveal the underlying electromagnetic mechanisms. Furthermore, the study identifies optimal coating thickness ranges depending on operating conditions, providing practical design guidelines for enhancing SRIM performance in high-speed applications.