SC-44 Siemens Charger Locomotives

ok a prime mover is the the main diesel, it does not take or convert electricity.

So just to get this right, and get the right terminology:

Prime mover, aka diesel power generator, generates AC... which is fed into a rectifier to convert it to DC, which is then regulated and fed into the traction motors and HEP inverters. Caternary AC would be fed into the rectifier as well. Third rail DC would just be regulated.

Geee... that sounds like some heavy power loss there in conversion. AC to DC back to AC... I gotta wonder the reasoning about that, unless it's hard to regulate AC going into the traction motors to get your speed range.

So "Prime Mover" is the component that supplies the energy, like the fire or the boiler or the steam on a steam engine.

What do we call it when the power is being supplied externally, like from the catenary or the third rail? Is "Locomotive" OK to call the whole thing? Something better/more appropriate?

Should we call the component that turns the wheels the "Traction Motor"? Something else? Would that be the same term for the rods and pistons of a steam engine?

The prime mover is the diesel within a locomotive, which you can't call an engine without confusing it with the whole locomotive as engine has been synonymous with locomotive since the steam era. The whole machine can be called a locomotive or engine regardless of being steam or diesel or electric.

Traction motors are called such as there are several types of motors on the typical locomotive, such as radiator fan motors. On some railroads the entire electric locomotive is referred to as a motor.

The AC-DC-AC conversion is done for control reasons, as the AC produced by the main alternator is not directly usable in the traction motors.

The big transformer comes from having to deal with 25 hZ AC current. If just 60 hZ would reduce the weight.

it would still be around 10 tons for a 4000 hp locomotive.

gokeefe wrote:Pretty sure the issue is AC. As I understand it the DC voltage on the third rail is basically the same as the voltage to the prime mover.

Not exactly. Prime mover is nothing more than a portable power plant providing electricity for the traction motors and HEP, so the "prime mover" in E-mode is literally the third rail or overhead wire bypassing the diesel power plant entirely (enough so that the diesel completely shuts off). Traction motors are all-AC these days because that's superior motor tech to older-style DC traction, and HEP is AC. Voltage gets stepped up/down, frequency-converted, and sliced/diced to various components accordingly; not every single thing runs at the same exact "raw" voltage as the source (most prominently: traction voltage vs. HEP voltage), so there is always a little bit of conversion going on as power is distributed to the loco's systems. A good, clean design with well-matched parts can help contain some of the complexity in juggling diesel prime mover vs. E-mode power sources and distributing them across all systems, keep the weight down, and keep the cost and maint complexity reasonable. This is why very highly vertically-integrated builders like Siemens, Bombardier, and in the past GE have a big leg-up on building workable duals vs. the small builders like MPI who don't have any 'pure' component selection hegemony or whatever pu-pu platter of various third-party vendor parts gets slapped lazily with an EMD builder's plate these days.


DC for E-mode is less costly and less bulky by weight and volume to equip a dual-mode locomotive with because DC power by its physical nature doesn't have to carry the transformers that any form of AC has to. That's why, for example, 1.5 kV DC Metra Electric has had bi-level EMU's for 40 years now with no major loss of seating from electrical components and third-rail dual locos into the tight confines NYP/GCT have been old hat for two-thirds a century...but you're only now seeing the first-ever FRA-compliant AC bi-level EMU's being ordered by NJ Transit and only now getting the morbidly obese ALP-45DP established as a mainstay fleet. Especially tough on the East Coast where it takes two AC transformers--one for 60 Hz and a much heavier one for 25 Hz--and ability to tap up/down from 12.5 kV to 25 kV to be able to have an AC vehicle that's fully portable across the NEC.


New York might've considered splitting the Empire and MTA orders AC vs. DC if a modular "Charge-Sprint" could offer both flavors at the same unit price. But Siemens would have to sell the AC's at a modest loss in order to offer identical pricing, because the very nature of AC (and especially the mixed bag of multi-voltage, multi-frequency AC on the NEC) means paying for the transformer components you don't have to pay for with DC. And maintain them, too. So New York has no motivation to split the orders. If the combo order is going to be approaching 90 units, they can probably buy a half-dozen or more DC duals just from the component money they'd be saving not having to buy AC transformers at all for the Empire contingent's E-mode cabinets. Unless the state gets NYP-ALB electrified at 25 kV AC for NYHSR before the heat death of the universe, it's always going to be more worth their while to pursue the ordering scale of the DC/third-rail variant to its logical end.

Though, like I said in the last post...sell 100 DC "Charge-Sprints" with 20-year Service & Support packages to New York and it just got a HELL of a lot cheaper and easier for the next buyer to take a realistic gander at the AC version. If the only major difference is the extra transformer junk that gets stuffed in the E-mode cabinets for AC...then having that huge an installed base of every other modular part in the loco brings the cost way down. So far down that it swallows the added cost of the unavoidable transformer extras and then some. That's scale the ALP-45DP can't economically reach in its current design incarnation because as a genset engine instead of a conventional prime mover it's the diesel half that blows out the Bombardier loco's cost of ownership. "Charge-Sprint" presumably being able to start out with the same stock QSK-95 power plant as the vanilla Charger means it'll have better cost control-via-scale on the half that'll be common to both DC and AC dual variants. When it's just the E-mode modules that need customization, and those E-mode modules are designed to require as few changes to anything else as possible whether they're plugged with DC or AC sources...then you start seeing some serious purchasing flexibility open up in the wake of New York's 75-100 unit order.

Loco alternator makes 3 phase 480VAC. overhead wire is single phase because there is only one pantograph. No matter what, it has to be rectified to DC for the DC link/smoothed out chopped etc then inverted back to 3 phase 480vac ac.

The DC 3rd rail situation is still complicated with new AC traction motor locomotives, but its easier to step up 750VDC to 1500-2000VDC for a DC link bus vs trying to step down 25kV 60hz to something acceptable for the locos propulsion system without the use of a heavy space hogging transformer.

Other than the transformer, all of the power electronics inverters/converters required for any of these types of engines with AC traction motors diesel, overhead, 3rd rail etc would be identical.

Yet another reminder of how unfortunate it is that Amtrak couldn't afford convert to 60 Hz when it was proposed in the 70's as part of the NECIP.

gokeefe wrote:Yet another reminder of how unfortunate it is that Amtrak couldn't afford convert to 60 Hz when it was proposed in the 70's as part of the NECIP.

60hz would not make much of a difference. 25kV would but bridge tunnel and penn station clearances as well as money spent on converters will prevent that for eternity.

gokeefe wrote:Yet another reminder of how unfortunate it is that Amtrak couldn't afford convert to 60 Hz when it was proposed in the 70's as part of the NECIP.

Converting from 25Hz to 60Hz made a lot of sense back in the days of the old rotating frequency converters. But now that frequency converters are solid state, this is no longer an issue. As for 25Kv south/west of New Haven, you'll probably never see it due to clearance issues. Look for 12.5Kv to be as high as the voltage goes wet of New Haven.

The lower the hertz , the heavier the transformer core needs to be . A heavy transformer built for 25hz can handle 60 hz no problem, you don't need 2 different transformers. But a transformer designed for 60 hz would be too light for 25 hz. So if you had to handle both frequencies , it would be designed heavy enough to do 25 hz, 60 hz is well covered . Different voltages can be handled by the same transformer , they just have different tapping points. which varies the number of windings to suit the voltage , or to get the same end voltage to the control side.
Modern inverters are very efficient, you are probably looking at 95 -96 % efficient , or a 4 - 5% loss. Maybe more at these higher voltages, Which I do not work with. But the principles are the same.

David Benton wrote:
Modern inverters are very efficient, you are probably looking at 95 -96 % efficient , or a 4 - 5% loss. Maybe more at these higher voltages, Which I do not work with. But the principles are the same.

To add to your post. Modern transformers are also very efficient. Don't know about them in RR application but power line transformers are now reaching 98.5% efficient. Power companies here are replacing older ones as fast as they can acquire them. Transformer production is just a little faster than CAF ! !

RRspatch wrote:

gokeefe wrote:Yet another reminder of how unfortunate it is that Amtrak couldn't afford convert to 60 Hz when it was proposed in the 70's as part of the NECIP.

Converting from 25Hz to 60Hz made a lot of sense back in the days of the old rotating frequency converters. But now that frequency converters are solid state, this is no longer an issue. As for 25Kv south/west of New Haven, you'll probably never see it due to clearance issues. Look for 12.5Kv to be as high as the voltage goes wet of New Haven.

Yeah...NYNH&H didn't overbuild its cat structures to the kind of electrification clearances Pennsy did so voltage upgrade is extremely hard in Connecticut. But the 60 Hz transformer handles both 12.5 and 25 kV voltages, so the hardware that does the voltage tap-up/tap-down wholly intra- 60 Hz territory isn't nearly as bulky as all the extra heft carried for running anywhere in 25 Hz territory. It's the reason why the M8's are captive to 60 Hz territory and don't have a 25 Hz core; they're already overweight needing to handle 750V DC and both 60 Hz AC voltages, so going with that heaviest of 25 Hz transformers would've put too much extra weight on the cars at too little benefit. To give an example of how much extra weight we're talking: SEPTA's Silverliner V's are virtually identical in all aspects to Denver RTD's Silverliner V's, but weigh 1 US ton more per car because SEPTA's cars were installed with the bigger 25 Hz core and Denver's were installed with the smaller 60 Hz core for their 60 Hz/25 kV electrification. That's how dramatic the difference is on an EMU with relatively small per-car propulsion; on a locomotive or Acela/Aveila power car packing a full trainset's worth of hauling power it's several tons' difference.


Frequency conversion gets sorta more palatable to consider now that the 4th Regional Plan is talking about run-thru commuter rail @ NYP. NJT has the bid out to replace the Arrows with the frequency-agile MLV EMU's, so that by 2021 all vehicles coming into Penn from the south will be able to switch between every AC flavor on-the-fly. You can now consider moving the 25/60 Hz phase break south into Jersey to the northern limits of Metuchen converter for the sake of running M8's to Newark, retire Sunnyside converter, and get the terminal district + everything south of the tunnels to approx. the junction with the NJCL on 60 Hz/12.5 kV. Then when SEPTA replaces the Silverliner IV's with frequency-agile new EMU's, every AC vehicle will be able to change on-the-fly and you'll have complete freedom to march down to Trenton and beyond changing over to 60 Hz. Unlike the scrapped Amtrak plans for a mass frequency change at a too-large billions in simultaneous cost, this time you'll be able to trudge south piecemeal one converter and X many power sections at a time in more reasonable budgeting increments spread over as many years at it takes. It may take until the current generation of brand-new vehicles are up for replacement before you trudge all the way through D.C. Union with a 60 Hz conversion and purge the last of 25 Hz, but hopefully by the time the Sprinters are at 25-year replacement and some sensible permutation of NEC FUTURE comes to fruition they'll finally be able to shop for rolling stock that has significant weight savings over today where every powered vehicle is lugging that extra 25 Hz tonnage around. If part or all of the network south of New Haven still has to remain 12.5 kV forever because painful clearance mods just don't wash on cost...no biggie, because voltage isn't the changeover that's making every piece of AC power equipment lug so many extra tons of hardware like the 25/60 frequency divide is.

It seems to me that ultimately it would almost make more sense to bit the bullet and move as much to one standard on the NEC as possible. It seems it would simplify the locomotive side quite a bit if for example we did move to one frequency.

I know as you say moving to one voltage is a real bear, but dang, do different standards suck.

Of course I need to toss this out: https://xkcd.com/927/" onclick="window.open(this.href);return false;