So I got to thinking about HEP. With my research into the F40PH one of the drawbacks of the HEP system is that if you needed more electrical power you could not just simply use the output of multiple locomotives. Say you had a large Amtrak train with a bunch of Superliners only one of the locomotives up front could supply HEP if you need more HEP power you would have to "split" the trains power system and have another locomotive at the end of the train to supply the back half of the train and have the two systems separate. I guess Synchronizing multiple three phase generators was to tall of an order in the 1970's. Has this problem been solved and if so when? Also do they offer HEP packages that don't require the prime mover to always be going max speed when you have a unit tat has HEP generated off the prime mover?

Synchronizing two generators isn't too hard but if done manually, it would require someone to keep an eye on them and make adjustments. Which would kinda stink if they were, say, at opposite ends of the train. It's much simpler if they are in the same place, and there are plenty of generator control panels available now that fully automate the process.

regardless of the generators used, Amtrak HEP uses 4 connectors rated 400 amps each. 1600a*480vac*1.73=1328640kva, typical power factor is .8 so your limited to (roughly) 1 megawatt of power, which is not an especially large generator/engine when talking in railroad terms. Sources suggest 800kw (0.8 megawatt) is a typical capacity for one HEP locomotive. Once you hit that limit the only practical way would be to split the train and use a separate HEP system.

That HEP limitation is pretty much what limits the length of the Auto Train's passenger consist to about 18 Superliners. They converted the lighting to LED about 10 years ago to cut power consumption enough so they could add a car or two during peak seasonal demand times.

Yes, more modern HEP generators than the original F40 screamers do not require the engine to be running max speed. It's magic to me.

I think they vary the field exciter voltage in the generator windings.

Might have something to do with a flux capacitor.

Brian Helfrich

Old and new:

I have a memory that the P30CH Amtrak locomotives could synchronize more than one HEP power plant, but they have been the only ones.

Also, the new models of Stadco generators (under slung for passenger cars) will auto synch, and in addition, start and stop the motors as needed for the load presented. I was talking to them at the RPCA conference in Jan -- this is of major interest to me with the SP 3602 rebuild project that is underway. This solves the problem presented by Tier 4 emission requirements which start to take to too much space in a limited space situation when you get into higher HP motors.

I would wager that modern control systems make synching magic pretty easy.

-dc

The P30's had two 375Kw Detroit plants that would sync. The converted power cars and Amtrak's HEP'd E8 locomotives were set up with similar equipment.

We never had much success syncing the pair on the Juniata E8's. I suspect it was old electronic technology and mechanical governors. The 12-V-71's were screamers...AKA the "Buzz'n Dozen "

EBL

When running modern emissions units, running at higher load levels is basically a requirement for better performance and less trouble. The rental generator market is suffering greatly because they often spend large amounts of time at light loads. Phasing in and out generators to keep the load high will improve life, emissions, and fuel economy, and should well compensate if a unit goes down. But it takes good controls to do it well.

I'm not an electrical engineer, but my understanding is that the "split" was necessary because synchronizing two HEP generators would have put more power into the HEP cables than the cables were capable of transmitting.

FWIW, Utahrails.net says that Amtrak's HEP cabling and connectors are capable of passing 1,200 kW of power, while wikipedia's F40PH article says those locomotives produced 800 kW of HEP power. 800+800 = 1,600, which is more than 1,200

This, as designed. GE pretty much designed Amtrak's original HEP implementation.

GE having designed and built a good portion of the US power grid, obviously knew how to sync an AC circuit. The problem is, its tricky. If your doing it manually. But thankfully, GE knew how to make control equipment that did it automatically.

You can find the P30CH operators manual online, and see exactly how the HEP system was suposed to work.

When using the P30CH units in tandem, up to FOUR of the 375KW generators could be online at once, to provide the full 1,200 kW capabillity.
(Yes I realize that would give youa theoretical 1500KW, but the wires max out at 1200KW, and it was designed to safety trip out if you exceeded 1200KW. Four online eased the strain on them at such high demand)

The P30CH units had a special jumper you would connect between them. This would allow the HEP units to talk to each other.

I say talk, as the system was suposed to be automatic. It was suposed to be able to start and auto sync 1 to 4 HEP sets as demand needed. (Or 1 to 2 if you had a single P30CH)

The same setup was installed into some HEP cars, and five of the mentioned E units. But these lacked the extra cable to sync four units, so they were limited to 1 to 2)

The sets in the HEP cars, and the E units were suposed to be put in the SDP40F when Amtrak got enough HEP cars around, but that obviously never happened.

As you can imagine for an overly complex system from the 70s... well it had issues.
On the P30CH it didn't help that they were sitting cramed in the back of a grumpy U boat.
It often malfunctioned, and an Amtrak electrican would set up the system in manual mode at the origination point.

The last HEP car I knew of was 688 up on the CVSR, but I have no idea if its still setup in the dual 375KW method.

The wire limitation is measured in kva, not kw. kva is what the conductors are doing, kw is what the engine is doing. You'll likely hit the kva limit long before you get to 1200kw...

The rated maxiumum permissible limit of the Amtrak hep system is 1200KW in KW.
https://www.nwrail.com/HEP_config.html
(providing you have a generator (or other source) that can push that much)

While most diesel HEP generators can't get near that. electrics did. And most ground HEP setups are 1200KW by default.

The E60MA had a ginormous motor generator set that could blast out 480VAC like nothing else. A simple setup, it was a single phase 25HZ motor connected to a 60HZ 480VAC Three phase alternator. Inefficent but effective. I never saw a max KW rating on the setup, but as big as the setup was. I bet it was a lot.

Few trains Amtrak ran or runs even come near that value though.

That said, The current Siemens products, diesel and electric, can provide up to 1000KW in 480VAC three phase with a single inverter.