Why can't MARC train run in the "dark"? - broke down yesterd

Yesterday, a MARC train broke down after leaving Union Station.

An MTA spokesperson told ABC 7 earlier Monday these trains can have problems in the heat and temperatures were around 90 degrees. I guess it what using an locomotive.

What I don't understand is why the train can't operate without electricty. VRE has sometimes let trains run "dark" - that is without lights and AC, if they are unable to get the HEP working, to prevent a major delay. Last week Train #307 had diffculties with the HEP, but they were able to fix it at Crystal City. And of course, VRE conductors made announcements, whereas last night MARC conductors did not when the power failed.

http://www.wjla.com/news/stories/0610/748135.html

davinp wrote:What I don't understand is why the train can't operate without electricty.

Because it was probably using an electrically powered locomotive.

It's not that. It's just a matter of safety. Conductors have to see where they're going and people have to see where they're going to get off the train otherwise someone would wind up hurting another person. I don't really see of any train that operates completely in the dark.

OK, I'm not a mechanic, but these HHP failures tend to occur when the temperature is above 90 degrees. Somebody should wire in a transfer switch so that if the motor fails, power from the pantograph can still be routed to the lights and A/C to keep the passengers comfortable.

jstolberg wrote:OK, I'm not a mechanic, but these HHP failures tend to occur when the temperature is above 90 degrees. Somebody should wire in a transfer switch so that if the motor fails, power from the pantograph can still be routed to the lights and A/C to keep the passengers comfortable.

It doesn't work like that. HEP on those electrics depend upon the motors working.

"gp40marc69"
It doesn't work like that. HEP on those electrics depend upon the motors working.

Actually it's more complicated then that. The contact wire is 11.5 kv single phase AC. The HEP is 480v 3 phase AC. The traction motors use 3 phase AC as well, though the voltage and frequency varies depending on RPM. If one or more of the devices between the contact wire and the output on the inverters craps the bed you have no power for HEP and no power for propulsion.

Sand Box John wrote:Actually it's more complicated then that. The contact wire is 11.5 kv single phase AC. The HEP is 480v 3 phase AC. The traction motors use 3 phase AC as well, though the voltage and frequency varies depending on RPM. If one or more of the devices between the contact wire and the output on the inverters craps the bed you have no power for HEP and no power for propulsion.

I expected that the voltage needed to be stepped down. I didn't realize the air conditioners were 3-phase though.

Sand Box John wrote:"gp40marc69"
It doesn't work like that. HEP on those electrics depend upon the motors working.

Actually it's more complicated then that. The contact wire is 11.5 kv single phase AC. The HEP is 480v 3 phase AC. The traction motors use 3 phase AC as well, though the voltage and frequency varies depending on RPM. If one or more of the devices between the contact wire and the output on the inverters craps the bed you have no power for HEP and no power for propulsion.

Thanks for clearing that up. I know on the diesels, they have a seperate HEP engine (Cummins QSK I think).

MARC diesel powered trains do "run in the dark." Yours truly has been on many Brunswick Line trains where HEP was lost, and not a single one stopped operating because of it (except in rare cases when the locomotive failed completely). Sometimes we would pause longer at a station if the train was in push mode so the conductor could go back to the engine and try to fix the problem. Sometimes it would be fixed easily, sometimes it would be temporarily fixed then go back out, and sometimes it couldn't be fixed at all. Regardless the train would continue as usual. Even without HEP there are still battery powered emergency lights still on about every 3 or 4 lights on both sides. Of course there's no HVAC though.

realtype wrote:MARC diesel powered trains do "run in the dark." Yours truly has been on many Brunswick Line trains where HEP was lost, and not a single one stopped operating because of it (except in rare cases when the locomotive failed completely). Sometimes we would pause longer at a station if the train was in push mode so the conductor could go back to the engine and try to fix the problem. Sometimes it would be fixed easily, sometimes it would be temporarily fixed then go back out, and sometimes it couldn't be fixed at all. Regardless the train would continue as usual. Even without HEP there are still battery powered emergency lights still on about every 3 or 4 lights on both sides. Of course there's no HVAC though.

I've had that happen on the Camden Line with a couple of the GP39s. The HEP had stalled and power went out. When we got to the next station, one of the conductors powered down the engine and started it back up and the power came back on. It also happened with one of the new MP36s (probably a glitch).