P32AC-DM Dual-Mode Genesis Discussion (Empire Service)

[MrDowntown]

The Wikipedia article on the Genesis P-32AC-DM says there's a 10-minute limitation on third-rail operation. Can anyone help me understand why?

My understanding has always been that diesel-electric locomotives are merely electric locomotives that carry a power plant around with them. Why would getting the motor current from a third-rail shoe rather than the generator bus be something only possible for a few minutes at a time?

I never heard of any time limitations on the FL9's run for many years by the New Haven (and successors) that switched to third-rail shoes so they could shut off the diesels for the Grand Central approach.

[Gilbert B Norman]

I'm going to defer to others "who do this stuff for a living" as to the necessity, Wiki author notwithstanding, to limiting time in the third rail mode.

The only thing I can add is that by the time a New Haven FL-9 had reached 125th St, the prime mover was fired up.

[DutchRailnut]

no 10 minute restriction on P32acdm, but because there is no dynamic brake in 3th rail mode and chance of arcing at higher speed might cause damage, MN has a operational restriction.
to run further north than cp5 in electric mode you must have permission from operations center, only used when there is trouble with diesel.

Amtrak does not need such a rule cause there is no third rail on Empire connector and going to Sunnyside would signal wise not get you much near or over 60 mph.

[Railjunkie]

If I remember correctly from my days at Choo Choo U, don't go past the fifth notch and top speed would be about 60mph but only for a short period of time. Think it had something to do with the fact you were changing 700v DC to AC through the inverters. There is no dynamic brake in third rail mode but unlike Metro North we can bail off the engine brake so there would be no chance of frying the grid.

But as Dutch says we at Amtrak only use the third rail into and out of Penn, no third rail on the empire connector and a top speed of 25mph in the tunnel and 15mph in the station.

[DutchRailnut]

at MN we run them in notch 8 as soon as were in tunnel, switching modes you do in notch 2 or 3, it changes modes faster than at Idle.
The dynamic brake inverter is used as step up (bus) inverter in E-mode stepping 700 v Dc up to 1400 VDC for inverters.

[jhdeasy]

There is third rail on the Empire Connector, but only between Penn Station thru the tunnel to CP Empire.

http://www.dominionrailvoyages.com/empireconnection.jpg

However, I've gotten the impression that the engineers usually operate their trains thru the tunnel in diesel mode, making the transition between diesel mode and electric mode in the open cut between the west end of Penn Station and the south portal of the Empire Connection tunnel.

[Railjunkie]

That would be the Empire tunnel where the third rail is located not the connector. Mode change is generally done at CP Empire when coming into Penn. I always try to have it completed before I reach the end of the U portion of the tunnel, that way if a problem should arise I can fire up the diesel and hopefully get permission into the station with it running. Leaving I start the mode change once I get off the ladders and onto solid third rail. I prefer not to finish the switch over until Im almost out of the tunnel account the grade and the curves act as one giant brake and these things don't load up all that quick.

[MrDowntown]

Returning to my original question:

The [Toronto-region] GO Electrification Study Final Report Appendix 4, p. 17, says

Further, only the LIRR DM30AC locomotives have thermal ratings that allow them to operate continuously in electric mode; the Amtrak and MNR P32DM AC locomotives have short-term ratings that limit their use to about 10 minutes of operation to and from the electrified tunnels of New York. These limitations stem from a very localized service environment restriction and associated locomotive design objectives.

What are these "short-term ratings that limit their use to about 10 minutes of operation?"

[EM2000]

Both the GE, and EMD Dual Mode Locomotives are Diesel Locomotives that happen to have the capability to draw off the 3rd rail to get them in and out of the tunnel. Diesel Locomotives are not "Electric Locomotives that happen to carry an engine around with them." There is no mechanical limitation for use in E-Mode on the DM30AC, although it is only used in, and out of the East River tunnels. I am sure the GE, being an AC traction Locomotive as well, does not have a limitation as whatever quote you posted above states. Again, these are Diesel Locomotives, not designed from the ground up to take DC power off a 3rd rail.

[mvb119]

Returning to my original question:

The [Toronto-region] GO Electrification Study Final Report Appendix 4, p. 17, says

Further, only the LIRR DM30AC locomotives have thermal ratings that allow them to operate continuously in electric mode; the Amtrak and MNR P32DM AC locomotives have short-term ratings that limit their use to about 10 minutes of operation to and from the electrified tunnels of New York. These limitations stem from a very localized service environment restriction and associated locomotive design objectives.

What are these "short-term ratings that limit their use to about 10 minutes of operation?"

I've been on a Metro North Hudson Line train at least once that operated from Grand Central to Croton Harmon in Electric Mode after the engine had issues, that is a distance of 33 miles.

[Tadman]

I'm curious if there are any special instructions or considerations for operating straight electric all the way to Harmon. We always hear a lot about how they can't or shouldn't operate that far as straight electric.

[DutchRailnut]

no GE restrictions , but doe to lack of dynamic brake in E mode, and huge chance of arc damage , MN restricts them to running in Emode south of CP5 only.
if engine has to operate in E mode North of CP5 we need permission .
no one likes to pull arcs at 1200 amps and 700 volt, a average arc welder is 125 amps at about 35 volt just saying.

[mohawkrailfan]

Do the P32ACDMs operate electric all the way between NYP and Sunnyside?

[DutchRailnut]

all way ?? a whopping 3 miles

[Tadman]

I get that arcs are not desirable, but I see accelerating subway cars drawing huge arcs in the rain all the time, and I see catenary-powered EMU's pulling similarly large arcs on damp evenings (when you can see the arcs and the conditions are right). Aren't those as bad, or perhaps worse since the wire is a much smaller conductor than a rail?