A few questions from a newb

BTW, I've heard that one issue biting WMATA ops is the power consumption of stopped cars has been going up over the generations...

Enough so that it is now a factor in backed up circumstances such as the Red Line now suffers from.....

"farecard"
BTW, I've heard that one issue biting WMATA ops is the power consumption of stopped cars has been going up over the generations...

Enough so that it is now a factor in backed up circumstances such as the Red Line now suffers from.....

I don’t know if you have been following the WMATA 7000 Series to have CCTV, Electronic Maps thread, I was stunned to learn that the power consumption of the cars have become greater with each new series.

Wikipedia Washington Metro rolling stock

To give you an idea of the progression. The 1k series Rohr cars when delivered were 500 Hp per car. The 5k series cars are 938 Hp per car. The 7k cars are estimated to be 814 Hp when they turn their wheels for the first time.

The weight of the cars has increased as well from the as built weight of just under 72,000 lb for the 1k series Rohr cars to something over 80,000 for the 6k series Altsom cars.

I will note WMATA has had a program underway sense 2004 to upgrade their 88 traction power substation to accommodate the newer power hungry rolling stock.

2004
4 Megawatt = 60
6 Megawatt = 21
7 Megawatt = 0
8 Megawatt = 2
9 Megawatt = 5

2013
4 Megawatt = 9
6 Megawatt = 15
7 Megawatt = 51
8 Megawatt = 2
9 Megawatt = 11

More the half of the upgrades have been completed.

The N route Silver line will have 19 substations all of the will at minimum be 6 Megawatt.

Sand Box John wrote: I don’t know if you have been following the WMATA 7000 Series to have CCTV, Electronic Maps thread, I was stunned to learn that the power consumption of the cars have become greater with each new series..

I'm less surprised by their increased traction demand than the standby. Do the new cars have 3X the AC cooling or such? You'd think the LED illumination saved power....

quote="farecard"
I'm less surprised by their increased traction demand than the standby. Do the new cars have 3X the AC cooling or such? You'd think the LED illumination saved power....

There is a hell of a lot more hardware aboard the trains that consume power then there was before. Diagnostic logging system, vehicle monitoring system, event recorders, hardware to drive the LED displays, hardware for the door announcement system. . . I would hazard a guess the power electronics in the propulsion system also consume power when the train is not moving.

Sand Box John wrote:

There is a hell of a lot more hardware aboard the trains that consume power then there was before. Diagnostic logging system, vehicle monitoring system, event recorders, hardware to drive the LED displays, hardware for the door announcement system. . . I would hazard a guess the power electronics in the propulsion system also consume power when the train is not moving.

All the listed new toys will consume watts but not kilowatts. And the LED illumination should be saving power.

From what I know of variable frequency drives, they should not waste anything noticeable at idle. Power is a large budget item to WMATA or any rail ops; and their purchase decisions will reflect that. Ergo, the designers will also have that in mind.

Which leaves me wondering....

I had thought that the point of upgrading the substations was mainly to support 8-car trains throughout the system.

JackRussell wrote:I had thought that the point of upgrading the substations was mainly to support 8-car trains throughout the system.

True.... but it's interesting to observe other aspects of the bigger problem...

"farecard"
All the listed new toys will consume watts but not kilowatts. And the LED illumination should be saving power.

From what I know of variable frequency drives, they should not waste anything noticeable at idle. Power is a large budget item to WMATA or any rail ops; and their purchase decisions will reflect that. Ergo, the designers will also have that in mind.

Which leaves me wondering....

When you total up all of the cars that have some or all of those toys those watts become kilowatts.

I still believe the greatest amount of the increase in power demand can be attributed directly to the more then 50% increase in the traction motor horse power.

"JackRussell"
I had thought that the point of upgrading the substations was mainly to support 8-car trains throughout the system.

The traction power distribution system was originally designed to support 8 car trains that had a total of 4,000 hp, not 8 car trains with a total of 6,848 to 7,504 hp.

Sand Box John wrote:
When you total up all of the cars that have some or all of those toys those watts become kilowatts.

But the traction motors draw (using your data) 6.8 to 7.5 MEGAwatts. Even if you took a kilowatt per train for controls, that's 0.015 percent of the traction load.

I still believe the greatest amount of the increase in power demand can be attributed directly to the more then 50% increase in the traction motor horse power.

As I would, too. But the HVAC must be a significant percentage of the load when not moving. Unlike a building AC system, the cars must cope with the massive amounts of air exchange every time the doors open. I don't have any cites as to how significant, though.

"farecard"
As I would, too. But the HVAC must be a significant percentage of the load when not moving. Unlike a building AC system, the car's must cope with the massive amounts of air exchange every time the doors open. I don't have any cites as to how significant, though.

I don't recall what the BTU capacity of the AC units are, but it's not insignificant. According to a document I found at bart.gov, the power consumed by the HVAC on their 70' cars ranges between 13.2% and 16.4% of the total power consumed by cars. Another document I found on the Kawasaki built NYCT 60' R143 is 2 HVAC units rated at 91,725 BTU / 7.5 tons.

Sand Box John wrote: According to a document I found at bart.gov, the power consumed by the HVAC on their 70' cars ranges between 13.2% and 16.4% of the total power consumed by cars.

And BART's climate is far milder than DC's; both summer's 90^2 and needed heat in the winter....

"farecard"
And BART's climate is far milder than DC's; both summer's 90^2 and needed heat in the winter....

13.2% to 16.4% of total power consumed is still a significant amount.

There is the quote that has been improperly attributed Mark Twain. "The coldest winter I ever spent was a summer in San Francisco."

John in the sand box of Maryland's eastern shore.

Sand Box John wrote: There is the quote that has been improperly attributed Mark Twain. "The coldest winter I ever spent was a summer in San Francisco."

I know that quote well. In general, it's cheaper to heat in the winter than cool/dehumidify in the summer. People dress for a snowstorm, and if you give them even 45F and no wind, they'll be warm enough.

I don't know if BART has a scheme to reuse waste heat from traction motors but other systems have in year past.

Sand Box John wrote: Another document I found on the Kawasaki built NYCT 60' R143 is 2 HVAC units rated at 91,725 BTU / 7.5 tons.

So as a SWAG, those 91KBTU/Hr units draw about 50KW each. So the eight car train might draw 800KW, a lot but also less than traction's ~7 MW.

New question

What if you tap in but dont tap out?
Or if you dont tap in but do tap out?

The reason I ask is because of the following:

With the free shuttle buses, the connection stations have wide open gates for everyone to use, meaning a lot of people dont or forget to tap out if its their last station or if theyre entering the system.

Another way this can happen is during rush hour when the gate is open from the person in front of you and you think you tap but it doesnt register