The demand for higher efficiency, power density, and power quality in aerospace motor drives has led to the adoption of Silicon Carbide (SiC) MOSFETs in these designs, which enable more efficient operation and faster switching times. SiC MOSFETs are susceptible to higher fault currents than IGBTs, which reduces their short-circuit withstand time to the point that conventional fault protection methods are not effective. In this presentation, conventional methods for converter hard fault protection are discussed, and it will be shown why they are insufficient for protecting SiC MOSFETs. Rogowski coil-based current sensing offers a promising solution for fault detection and mitigation for converters using SiC. These coils utilize an air core which provides several advantages: they are lightweight, convenient to integrate into an existing converter assembly, and are at no risk of magnetic saturation. The low inductance of these coils is acceptable due to the large current derivatives of the hard fault events. During this presentation, our prototype Rogowski coil-based fault detection system will be shown, including its design, simulation, and successful testing. The system was able to stop a low-inductance (<400nH) fault on a 1kV bus within 500ns with no observable damage to the converter. Analysis shows that this design can keep both the SiC die and the device’s bondwires below their maximum operating temperature during a fault event. This Rogowski coil-based system is currently integrated in the Advanced Air Transport Technology Power and Propulsion (AATT P&P) 250kW, 1kV prototype aerospace motor drive. The system is also incorporated into the design for the 37.5kW Motor And Generator Intelligent Controller (MAGIC) converter for the SUbsonic Single Aft eNgine (SUSAN) 25% scale flight research vehicle.
