BART Begins Fleetwide Silicon-Carbide Traction Inverter Upgrade at Hayward Maintenance Complex

Rolling-stock propulsion engineers with Bay Area Rapid Transit (BART) completed revenue acceptance testing on Friday morning at the Hayward Maintenance Complex on Whipple Road for the agency's next-generation Silicon-Carbide (SiC) traction inverter retrofit program, clearing the way to upgrade 120 Fleet of the Future railcars over the next fourteen months. Approved by the BART Board of Directors under the agency's 2030 Wholesale Clean Electricity and Efficiency Strategy, the solid-state wide-bandgap MOSFET propulsion modules replace first-generation silicon Insulated-Gate Bipolar Transistor (IGBT) units mounted in the underframe equipment bays. Because silicon-carbide semiconductors switch 1,000-volt DC third-rail current with minimal thermal resistance, the new inverters cut switching heat losses by more than half.

During four weeks of instrumented revenue trials along the Berryessa/North San Jose to Richmond and Antioch to San Francisco International Airport corridors, onboard energy meters recorded a 39.4 percent regenerative braking recovery rate—up from 31.2 percent on baseline cars. Every time a ten-car train decelerates into stations such as Oakland 12th Street, Walnut Creek, or Embarcadero, its traction motors act as generators, feeding clean electricity back into the third rail to power accelerating trains nearby.

Across BART's 131-mile five-county system, scaling the silicon-carbide inverter upgrade is projected to save 14.2 gigawatt-hours of traction electricity annually, reducing operating power bills by $2.4 million per year while lowering summertime heat buildup inside the Transbay Tube and downtown subway stations. The higher switching frequency also eliminates the high-pitched electromagnetic inverter whine previously audible during platform departures.

The $18.5 million propulsion modernization is funded through a Federal Transit Administration Rail Vehicle Replacement and Efficiency grant matched with California Low Carbon Transit Operations Program carbon credits. Riders and transit researchers can view quarterly traction energy dashboards and fleet reliability metrics on the BART Sustainability and Performance Portal.