A GaN Clamping Circuit for Mitigating Overvoltage Transients in Inverter-Fed Motors

This article presents a Gallium Nitride (GaN)-based bidirectional clamping circuit that suppresses internal overvoltage across the first motor turns when no cable or a short cable is used between the motor and the drive. The circuit uses a high-speed analog detection scheme and self-powered architecture derived from the motor terminals. Five gate driver technologies, including capacitive, magnetic, optical, transformer-based drivers, and GaN field-effect transistors (FETs) with integrated drivers, are experimentally compared using a success rate metric that quantifies the robustness of the clamping circuit in suppressing MHz overvoltage transients. Success is defined as timely detection of the transient and full turnonof the GaN device to clamp the first overshoot voltage. Capacitive and optical drivers achieve the highest success rates of$\textbf{83\%}$and$\textbf{72\%}$, respectively, with a$\textbf{3 m}$cable between the drive and motor. Although the success rate decreases slightly in the no cable configuration, it increases to as high as$\textbf{99\%}$with longer cables. When successful, the clamping circuit reduces peak coil overvoltage by approximately$\textbf{42\%}$. The complete system is experimentally validated using a rewound$\textbf{2 hp}$induction motor to demonstrate scalability and effectiveness under practical operating conditions.