An apparent power surge is causing trouble for BART in the Transbay Tube, which means fewer trains – and more crowded ones – for thousands of commuters.
The mysterious electrical problem was first reported by the San Francisco Chronicle. And BART announced on Friday the immediate problem had been fixed, though the root cause of the voltage fluctuation hadn't been determined.
BART spokeswoman Alicia Trost said the cars traveling eastbound make it through the tube - they don't slow or get stuck - but for some reason the power along a section of track is too high. She described the issue as a “propulsion failure.” On Monday, she said, 40 cars, experienced this type of failure, and a total of 80 cars out of the total fleet of 230 are affected, she said.
The cars have four direct current motors driven by a semi-conductor, which has protective circuitry, she said. It appears that the power reaching the cars is at too high a voltage and the C cars’ protective circuitry is not strong enough to protect one particular component, she said, noting the A and B cars seem to be more “resilient.”
Although BART has had this problem intermittently for some time, Trost said it became more frequent starting on Feb. 20.
Trost said certain cars seem to have more trouble with the track than others, and that means they have to use shorter trains until they solve the problem.