EMD E unit electrical system redundancy question

PRR 5841 posted:

Gentlemen,

If one of the two diesel/DC generator sets shuts-down for some reason while pulling a train, does the current produced from the remaining operative diesel/DC generator set go to only one or both pairs of traction motors?  

Each engine generator, and its corresponding electric control circuitry, power ONLY the two traction motors in that truck specific truck. Thus, if one engine generator set "goes down", then THAT truck is unpowered.

I’m assuming that each diesel/DC generator set was permanently wired to one truck (2 motors) and isolated from the other.  

Correct.

 

Hot Water posted:

PRR 5841 posted:

Gentlemen,

If one of the two diesel/DC generator sets shuts-down for some reason while pulling a train, does the current produced from the remaining operative diesel/DC generator set go to only one or both pairs of traction motors?  

Each engine generator, and its corresponding electric control circuitry, power ONLY the two traction motors in that truck specific truck. Thus, if one engine generator set "goes down", then THAT truck is unpowered.

I’m assuming that each diesel/DC generator set was permanently wired to one truck (2 motors) and isolated from the other.  

Correct.

The normal diesel locomotive had one generator.  It would not make sense to have two generators each wired to a set of traction motors.  In any slow speed situation, one of two diesel engines would provide enough power for four traction motors.  IF only two motors were powered, the tonnage that could be moved at slower speeds would be halved.

What locomotives do you know had two generators ?

Malcolm Laughlin

I think the EMD E units had two MG sets.    Also I think the Baldwin Centipides did.

When those units were designed, it seems most diesel prime movers of the size that could be used in a locomotive were in the 1000-1500 HP range.    Hence to get a 2000 HP unit, EMD  used two prime movers.   

Diesels with 2000 and greater HP with one MG did not appear until the late 50s or early 60s.

I don't know how they were wired however.

I think MP had a variation of an E unit.  Hadonly one engine, and one powered truck.  The space for the other engine was used for baggage.  E uint meets motor car.  Used in LA in branch line service.

It would not make sense to have each generator wired to a single truck.  And I fell pretty sure that the throttle did not have two completely separate sets of wiring.  With only one engine, you would not want to have power to only one of the trucks.  That would have made it impossible to start a heavy train because of wheel slippage.  With four motors getting power from only one engine, you could at least start the train but you would have a much lower top speed.

Believe it or not, that’s how E units were set up...

One thing I've learned on this forum is that Jack (Hot Water) is rarely incorrect based on his history of working for EMD and still being a certified steam locomotive engineer.  Not that it isn't important to check sources, but Jack is a huge database of knowledge.  He has helped me numerous times on various 3rd Rail projects.  Just my 2 cents.

mlaughlinnyc posted:

It would not make sense to have each generator wired to a single truck.  And I fell pretty sure that the throttle did not have two completely separate sets of wiring.  With only one engine, you would not want to have power to only one of the trucks.  That would have made it impossible to start a heavy train because of wheel slippage.  With four motors getting power from only one engine, you could at least start the train but you would have a much lower top speed.

It actually does make sense as two DC generators MUST be isolated from each other or else the one with the higher voltage would destroy the other.  Hypothetically speaking, using alternator/rectifier technology, still a few years away after the last E9 was built, two alternators running in parallel on a common AC bus could be rectified to a common DC bus to power all DC traction motors.  Should one alternator fail, the remaining operative alternator would still be able to supply ALL traction motors albeit at reduced currents and lower top speed as you pointed out.  I doubt that Auto-Paralleling circuitry existed back then meaning the alternators would have to be manually paralleled after both diesels were started.  All this is academic as E units were designed to operate at speeds where maintaining all available current to all traction motors simply wasn’t as important as it would be in a freight locomotive frequently operating at high power/low speed.

mlaughlinnyc posted:

It would not make sense to have each generator wired to a single truck.

Well, it may notbmake sense to YOU, but that is EXACTLY how E Uints were designed and manufactured.

 And I fell pretty sure that the throttle did not have two completely separate sets of wiring.

No, the throttle didn't have "two completely separates of wiring", but all the commands from that single throttle went to both power plant electrical cabinets.

  With only one engine, you would not want to have power to only one of the trucks. 

Why not? That is indeed how the twin engined E Units were all designed, as well as the twin engined DD35, DD35A and the biggest DDA40X.

That would have made it impossible to start a heavy train because of wheel slippage. 

Do you have a lot of experience with real diesel electric locomotives? Also, lets remember that we are discussing EMC/EMD E Units, which were designed & developed for PASSENGER SERVICE. They were NOT drag freight locomotives.

With four motors getting power from only one engine, you could at least start the train but you would have a much lower top speed.

Really? How did you come to that conclusion? Again, how much experience do you have with real railroad diesel electric locomotives?

prrjim posted:

I think the EMD E units had two MG sets.    Also I think the Baldwin Centipedes did.

When those units were designed, it seems most diesel prime movers of the size that could be used in a locomotive were in the 1000-1500 HP range.    Hence to get a 2000 HP unit, EMD  used two prime movers.   

Diesels with 2000 and greater HP with one MG did not appear until the late 50s or early 60s.

 

Fairbanks Morse Erie Built - 2000 hp Roots blower 10 cylinder 38D-8 1/8 opposed piston prime mover - December 1945.

Alco PA-1 - 2000 hp turbocharged 16V-244 prime mover - June 1946.

Stuart

The FM opposed-piston design was too expensive to maintain (lift out the top-crankshaft with a crane to change out a power-assembly) compared with the EMD 567 as was the underdeveloped Alco 244. Hence the success of the EMD 567 followed by the 645.

SP did have OP FM's in NM.  Later moved to the Bay Area.  Heard the OP did not like heat and/or sandy conditions.  Then again the OP was the prime mover for some US Navy Subs.

Dominic Mazoch posted:

SP did have OP FM's in NM.  Later moved to the Bay Area.  Heard the OP did not like heat and/or sandy conditions.  Then again the OP was the prime mover for some US Navy Subs.

Where it wasn't real warm or sandy...

The FM OP prime movers weren't totally without merit.  The Virginian Railroad diesel fleet was 99.99% FM (They had one GE 44 tonner.)

Rusty

The OP's worked better in the Bay Area also because they were all grouped in te same shop.  

IC I think was going to buy some FM's and the right to build them?

Dominic Mazoch posted:

The OP's worked better in the Bay Area also because they were all grouped in the same shop.  

IC I think was going to buy some FM's and the right to build them?

Dominic,

From what I've read IC was going to order 50 H24-66 Train Master diesels, but a hostile takeover attempt of FM turned them off.

Stuart

Stuart posted:

Dominic Mazoch posted:

The OP's worked better in the Bay Area also because they were all grouped in the same shop.  

IC I think was going to buy some FM's and the right to build them?

Dominic,

From what I've read IC was going to order 50 H24-66 Train Master diesels, but a hostile takeover attempt of FM turned them off.

Stuart

The number I've heard was 75 H24-66's.  I also read somewhere that the IC considered upgrading part of its passenger fleet with FP45's.

Now THAT would've been sumptin'...

Rusty

Dominic Mazoch posted:

The OP's worked better in the Bay Area also because they were all grouped in te same shop.  

IC I think was going to buy some FM's and the right to build them?

It was PRR who wanted rights to build the FM H-24-66 Trainmaster. PRR was also supposedly spying on or poorly trying to spy on EMD and their manufacturing. Pennsy management was really all over the place.

Sam Jumper posted:

Dominic Mazoch posted:

The OP's worked better in the Bay Area also because they were all grouped in te same shop.  

IC I think was going to buy some FM's and the right to build them?

It was PRR who wanted rights to build the FM H-24-66 Trainmaster. PRR was also supposedly spying on or poorly trying to spy on EMD and their manufacturing. Pennsy management was really all over the place.

And just how do you document THAT? Any and all railroad customers could tour the EMC/EMD McCook manufacturing facility any time they requested. In fact, part of the EMD Service Depart Training Center classes INCLUDED an extensive plant tour for EVERY CLASS!