Update on New BART Cars from Bombardier

[farecard]

What is the propulsion system of the new cars: VFD's+multiphase motors, chopper+DC, etc?

I looked through BART's pages on its new railcars, and there was no mention of any such technical details. Those pages mostly discussed what passengers will experience, like the railcars' floor plans and seats.

Thanks. WMATA started with DC motors with classic cam control in the 1000's, then in the 2000-3000 choppers.
The 1000's were rebuilt mid-life with https://en.wikipedia.org/wiki/Variable-frequency_drives & multiphase AC motors.
Newer builds are all AC motors.

I wonder if BART ever rebuilt DC cars with AC?

[AC motors are lighter, smaller diameter & have almost nothing to break. When both systems were born, VFD's just did not exist, especially at these power levels. Now they are off the shelf...]

[lpetrich]

I found something at BART's site that gives some technical details on the existing railcars' propulsion. Microsoft Word - BART.doc - BARTenergyreport.pdf
Title: Energy Efficiency Assessment of Bay Area Rapid Transit (BART) Train Cars -- San Francisco Bay Area

PDF page 13:

The propulsion systems in C1 and C2 cars consist of four direct current (DC) motors per car. ...

A and B cars are the first major rehabilitation project done to the BART cars. The main propulsion system was changed from DC motors to induction motors (IM).

All existing BART railcars have four 150-hp (112-kW) propulsion motors each, one per axle.

The A and B cars are the original BART ones, the C1 and C2 are more recent ones.

The energy budgets of the A/B and the C cars:

• Propulsion: 80.3%, 83.5%
• HVAC: 16.4%, 13.2%
• Everything else: 3.3%, 3.3%

This report recommended using permanent-magnet motors.

[lpetrich]

Whats up with the new renovated bart trains? | BART RAGE - Bay Area Rapid Transit Blogs
Member "former employee" stated:

C-cars have a DC propulsion system which uses power electronics called a chopper to control the motor current. The single frequency hum at 218 Hz comes mostly from the motor smoothing reactor which is just a large coil wound on a laminated steel core.

...

The rehabbed A/B fleet uses an AC propulsion system. The traction motors are three phase AC induction motors that are controlled by a variable voltage, variable frequency electronic inverter. The hum is a variable frequency that comes from the traction motors and depends on the speed of the car.

So the new railcars will likely use either induction motors or permanent-magnet motors, with variable-frequency drives for either kind of motor.

[farecard]

So the new railcars will likely use either induction motors or permanent-magnet motors, with variable-frequency drives for either kind of motor.

So your A/B's *were* rehabbed to AC at some point; that just makes sense.

I recall there was the de-nosing of them as well. (When BART was being built, legacy train folks strongly recommended against the noses because of the operational limitations they imposed. But I remember reading some local politician's quote - he insisted on them because [in effect] ~"We need something sexier/Jetson-like" to impress riders...." I guess he is gone now.)

Permanent-magnet motors [in anything above the toy size] became feasible only after I finished engineering school, so I don't know much. They use electronic switching to replace the brushes. They need "rare-earth" magnetic material.

In both PM & AC motors, it's the many orders of magnitude improvement in power semiconductors from ~1970 on that makes them usable with variable speed loads.

ps: That is a good link for details: http://bartrage.com/comment/15981#comment-15981

[lpetrich]

I recall there was the de-nosing of them as well. (When BART was being built, legacy train folks strongly recommended against the noses because of the operational limitations they imposed. But I remember reading some local politician's quote - he insisted on them because [in effect] ~"We need something sexier/Jetson-like" to impress riders...." I guess he is gone now.)

It's hard for me to find good sources on the removal of many of the original cabs. But I've found a reference to that removal in cars with "nose cones" | BART RAGE - Bay Area Rapid Transit Blogs

I recall from a history of BART somewhere that some of BART's designers had the idea of making the cabs removable and re-attachable. I'd have to track down the source, however. I also recall seeing a picture of some testing of three-phase alternating current for the trains. The picture showed three side rails stacked vertically.

In any case, the C cars all have flat cabs with doors at the ends, and BART's upcoming cab cars will be like that also.

[lpetrich]

Power system failures plague BART's new cars - EastBayTimes.com

BART's new fleet is scheduled to begin carrying passengers next year, but the shipment is already five months behind schedule, and the test cars suffer from design flaws that could impact their long-term reliability.

...
BART OK'd an initial order of 10 cars from Bombardier Inc., despite last year discovering problems with their auxiliary power supply equipment, or APSE, that could cause overheating. The system provides electricity inside the car for everything from lights, doors and communications systems, to a pump that replenishes brake fluid on the car's secondary braking system. Many of the systems inside the car can run safely on battery power, said project manager John Garnham, but the auxiliary units recharge the batteries, as well.

It's also a piece of equipment that has plagued BART's existing fleet, costing millions of dollars to replace.

[farecard]

I also recall seeing a picture of some testing of three-phase alternating current for the trains. The picture showed three side rails stacked vertically.

During the initial design, BART had an expansive test program for the best power system. I recall reading of it in IEEE Spectrum, I think it was.
They looked at AC & DC at various voltages, and ended up with DC at 1KV vs 650~750VDC.

[Fan Railer]

New BART train in motion from Bombardier: https://www.youtube.com/watch?v=Z5_H1DY_GuA" onclick="window.open(this.href);return false;

[tommyboy6181]

It sounds nearly identical to the outgoing Rohr cars in Washington, DC. Nice job on the train by Bombardier. It looks sharp.

[timz]

It's hard for me to find good sources on the removal of many of the original cabs.

Why do you think any cabs were removed?

[lpetrich]

Because the original cabs are not good for mid-train service. Passengers can't walk through them. BART's more recent cab cars are flat-ended, with doors in the middle. Thus making them suitable for mid-train duty. BART's upcoming cars have a similar design of their cabs, thus also making cab cars suited for mid-train duty.

[Head-end View]

Just amazing that the original planners of BART's fleet in the 1960's never thought of that. What fools!

[timz]

I meant, what makes you think original-style cab cars got converted to something else.

Reportedly BART's original 1969 order was for 150 cab cars and 100 midtrain cars-- and that's what Rohr ended up building? So that does raise the question, what's become of those cab cars. What were they converted to, and when?

(It seems they did get the 150 cab cars in the original order, plus 20+ more in 1974-75.)

[ExCon90]

Just amazing that the original planners of BART's fleet in the 1960's never thought of that. What fools!

There was a prevailing feeling in the 1960's that professional railroaders didn't know anything and new thinking was required; I don't know how many of the designers had practical operating experience. Two examples: 1) as I recall, a 4-second pause was built in after the doors closed until the train automatically started, intended to provide time for the last-boarding passengers to be seated; the same interval was built in between the train stop and the opening of the doors, evidently because someone envisioned the passengers remaining seated until the train came to a stop--obviously someone unfamiliar with contemporary rapid-transit operations--so that upon arrival at a station the detraining passengers, who were of course already standing at the doors, were obliged to stand there for four seconds until the doors opened. 2) An acquaintance was on a peer-review committee to evaluate the design of the cars while still in the design stage; on pointing out that the cars had no collision posts he was told "oh, this will all be computer-controlled--there won't be any collisions."

[Head-end View]

"And nothing can possibly go wrong, go wrong, go wrong............" LOL

They probably thought there would never be a fire in the Transbay Tube either. Remember that debacle in 1979 I think it was.

Sounds like a very misguided attempt at reinventing the wheel. Again I say: "Fools!"