An Integrated Smart Coil Solution for Reflected Overvoltage Mitigation in SiC Motor-Drive Systems—Comparative Evaluation

Abstract

The rapid adoption of fast-switching wide bandgap (WBG) semiconductor devices in motor-drive systems has introduced significant benefits in achieving high efficiency and high power density but also posed challenges associated with reflected overvoltage phenomena. Such reflected overvoltages impose severe high-frequency voltage stress on motor stator windings, which accelerate insulation degradation and undermine the reliability of motor stator windings. Traditionally, RLC $dv/dt$ filters have been used as an effective mitigation technique for limiting voltage slew rates and protecting the motor winding against these reflected overvoltages. However, these filters introduce excessively additional losses, size, and weight to the overall motor-drive systems. In contrast, the recently proposed smart coil circuit (SCC) has emerged as an alternative mitigation technique. This new approach enables effective suppression of reflected overvoltages with ultrahigh efficiency through its adaptive, ultracompact, and self-powered design. This article presents a comparative study of the smart coil mitigation technique versus the conventional RLC $dv/dt$ filter for overvoltage mitigation. The comparison focuses on operating efficiency, the effectiveness of mitigating overvoltage stress on motor stator windings, and identifying which mitigation technique is more effective for various operating conditions. Finally, comparative experimental validations based on a 2-hp motor-drive system demonstrate the effectiveness of both mitigation methods and provide an assessment of their strengths and limitations in WBG-based motor-drive systems.