# Train troubles in S.F. Bay area (BART system)

#### jgessling

Joined Jul 31, 2009
82
I'm curious if any of you with knowledge about high voltage trains can comment on this issue. Started a few weeks ago, train cars on our system have been knocked out of commission due to power spikes. That's a pretty vague description, but today's paper had a couple details. Please let me know what you think. Snippets from article at sfgate.com .

BART mechanics said Thursday that they were closer to pinning down the problem. They said 50 train cars that failed Wednesday were hit with a power spike as they moved through a track crossover north of the North Concord station. On that stretch of track the power is reaching up to 2,000 volts — twice what BART expects for normal operations.

#### Glenn Holland

Joined Dec 26, 2014
695
Here's the latest "No Brainer" explanation about what went wrong.

In the area where the electrical/electronic failures were occurring, the rails had been "re-profiled" or shaved with a high speed grinder mounted on a special track maintenance vehicle. This process left billions of steel particles on the track way that were stirred up when the trains went over the area and they were eventually drawn into the traction motors and electrical/electronic cabinets.

In accordance with Electricity 101-A, metal particles will conduct and cause catastrophic failures!!! There are also strong magnetic fields around the components with high current that will attract steel particles off the ground. However the 1970s vintage trains with DC traction motors (commutators) were especially vulnerable.

Since the 1980s, high voltage electronics in transit vehicles are mounted within sealed enclosures with cooling air directed over external heat sinks so the components never come in contact with the outside air.

#### MrChips

Joined Oct 2, 2009
19,914
Geez.

Even I would know that when I am drilling, grinding and filing holes on a metal chassis for an electronic project, it makes sense to vacuum out all the metal bits out of the chassis before assembling.

#### Glenn Holland

Joined Dec 26, 2014
695
Most railroads are not electric and metallic particles are not a problem.

However with 600 to 1000 VDC powered trains, metal particles can create problems big time -especially in tunnels where dust accumulates and never gets washed away by rain. I used to work at a rail transit agency in the San Francisco Bay Area and the tunnels and underground control rooms were absolutely filthy with dust of all forms. Minute steel shavings from wheel wear could be found on anything with a magnetic field, such as motors, relays, and transformers.

With all the contamination, it's a wonder there weren't even more failures.