The Future of Transportation

Solid State Transformers for Medium Voltage Fast Charging

Traditional charging station designs use low voltage power electronic solutions which increase costs and decrease efficiency. But NC State and other researchers are designing extreme fast chargers that use Silicon Carbide devices and pull power from the utility distribution grid at 13,000 volts or more. Silicon carbide power electronics can operate at much higher voltages and temperatures than traditional electronics based on silicon technology. This approach eliminates the 60 hertz transformer that normally steps the grid voltage down to 480 volts. Eliminating this low frequency transformer and associated low voltage switchgear decreases the overall footprint of the extreme fast charger, which is very important for fleet owners that may have space constraints.

High Power SiC Inverter for Heavy Truck Traction Drive

FREEDM researchers partnered with Ricardo Engineering to develop a 250kW traction drive for Class 8 Trucks. Design and testing of such an inverter presents unique challenges related to the high voltage, high current, and EMI involved. Peak current capability was confirmed using a practical recirculating current method which minimizes power supply and load requirements. Further power testing used an inductive and resistive load to mimic normal operating conditions. Final samples are being tested on drayage trucks at the Port of Long Beach in California.