Passenger Trains > Charger HEP

Tell me if I understand Charger HEP correctly.

The engine turns just one generator whose output is rectified and fed to inverters for the traction motors and an inverter for HEP.  If you are drawing no HEP you have 4400 HP* available for propulsion.  When you start drawing HEP, the power available for propulsion drops.  On paper, 1 HP = 746W so a kiloWatt would require about 1.5 HP but there is no such thing as perfect so with losses in the generator, rectifier, and inverter you can probably figure 2 HP per kiloWatt.  The more you draw, the less the pulling power.

The Amtrak long distance ALC-42 Chargers have a greater HEP capability than the state-owned SC-44s but if one is not running HEP at all don't they both have the same power available for traction?  Seems like that would be the case.  And surely the more HEP you draw, the less power there is for traction, just like an F40 where they used to sometimes turn off HEP when climbing mountains.

* Traditionally, at least in North America, the HP rating was generator shaft input meaning net of parasitic loads.  Which is why the same engine in non rail application would have a higher rating.
 

The earlier F40's, 200 class had a fairly weak HEP output. The HEP robbed 400 HP off the engine.So you had 2600 HP for traction.
BUT the 300 and later classes were robbed of 600 HP leaving them with just 2400HP for traction!
Even worse were the GE 3200 HP Dash 8 eights. They had a huge output of approx 750HP for HEP. We lost time on the San Diegans when
the Dash *'s were assigned to a consist. But they could supply a train with more than enough HEP. That was one reason you would see them MU'ed
with P40/42 on long distance trains that required a lot of HEP.
But one thing most people are unaware of was that the Dash 8's without the HEP cut-in were quite capable. They could really go and could out perform
both F-40 classes!
Leaving Needles with 2 F-40's, 300 class, on the "chief" (amtrak) the best we could go was about 45mph wide open. You wold lose time.( westbound)
The P-40's changed that and any overtime you once made with 2 F-40's were lost.


 

You are correct.  HEP steals power away from the wheels.  Electrical power, no matter where it is consumed, take engine power to produce.  I think the horespower to inverter output efficiency is much higher than 50%, probably closer to 90%.

Before inverters came along, the HEP AC frequency was controlled by the RPM of the HEP alternator.  That's why F40s had engines that didn't idle down during station stops.  The new systems are quite a bit better in terms of enigne power, wear and tear, and noise.



Edited 1 time(s). Last edit at 04/23/23 21:36 by radar.

I traveled from Florida with an ex-ICG engineer that ran the Chicago-St. Louis line for Amtrak.
I believe his name was Ray Cook.  He told me that he would sometimes aproach CUS, and put his F40 throttle at notch 5,
which is the other setting to maintain HEP, and the glide into Chicago Union Station.  Thereby avoiding the screaming
engine as people walked by.  The only problem was, if he didn't judge the distance right, and needed any throttle to
get closer to the bumping post, he would fall short.  True story!

Incorrect. The SC44s put out 4400 HP and have less of a HEP capacity compared to the ALC42s. Regardless of whether producing HEP or not the SC44s put out 4400 HP and the ALC42s put out 4250. The General Electric locomotives in the fleet lose about 600 HP when producing HEP, so a P42 is 4250 HP without HEP and 3600ish with HEP up.

Posted from iPhone



Edited 1 time(s). Last edit at 04/24/23 01:35 by 2904.

2904:
How is that physically possible if the QSK95, per Cummins brochure, puts out 4400 HP?  If the SC44 can put out 4400 HP even while putting out HEP, where is the power coming from?

filmteknik Wrote:
-------------------------------------------------------
> 2904:
> How is that physically possible if the QSK95, per
> Cummins brochure, puts out 4400 HP?  If the SC44
> can put out 4400 HP even while putting out HEP,
> where is the power coming from?

Exactly. That is not possible and some people simply did not do enough Physics to understand that LOL!

I have no idea, I just run them everyday and watch the fancy screens that say how much horsepower it’s loading. It’s one of the reasons chargers have so much more get up and go, they don’t lose any horsepower when producing head end power.

Posted from iPhone

https://www.cummins.com/engines/qsk95

The Cummins website says the QSK95 is capable of producing 3000-5100 HP.

Posted from iPhone

filmteknik Wrote:
--------------

> 2904: If the SC44 can put out 4400 HP even
> while putting out HEP, where is the power coming from?

He wasn't quite clear. No doubt he agrees
that the SC44 puts out 4400 hp total,
including HEP.

That's interesting about coasting into
Chicago with an F40. I knew F40s had that
HEP-only setting to quiet them a bit,
but I didn't know the engineer could
switch to it while the train was rolling.

Horsepower to rails regardless of producing HEP:

SC44 - 4400
ALC42 - 4200

The RPM does increase at idle by maybe 150 or so when producing HEP, but it’s barely noticeable.

The chargers also feed the HEP and auxiliary systems when in dynamic brake, although in full dynamic they produce far more power than the system can handle so they also dissipate energy through the dynamic brake grids.

Posted from iPhone



Edited 1 time(s). Last edit at 04/24/23 08:35 by 2904.

2904 Wrote:
-------------------------------------------------------
> Horsepower to rails regardless of producing HEP:
>
>
> SC44 - 4400
> ALC42 - 4200
>
> The RPM does increase at idle by maybe 150 or so
> when producing HEP, but it’s barely noticeable.
>
> Posted from iPhone

Now can you explain how 4 x 978HP induction motors deliver 4400HP to rail? ;) Something in the specification is a bit off. I am not sure what. But things just don't add up properly.

I agree. Beats me, why does the maximum continuous traction power in the manual say 4,200 HP and the TOD 1 screen say that range when the locomotive is number 8? Either way the engine doesn’t produce any more power to the rail when it’s not producing head end power, so from an engineer stand point I really couldn’t care less. That’s all I need to know when setting up a consist, especially when a charger is paired with a GE. You always want the HEP on the charger in that case.

Posted from iPhone

2904 Wrote:
-------------------------------------------------------
> I agree. Beats me, why does the maximum
> continuous traction power in the manual say 4,200
> HP and the TOD 1 screen say that range when the
> locomotive is number 8? Either way the engine
> doesn’t produce any more power to the rail when
> it’s not producing head end power, so from an
> engineer stand point I really couldn’t care
> less. That’s all I need to know when setting up
> a consist, especially when a charger is paired
> with a GE. You always want the HEP on the charger
> in that case.
>
> Posted from iPhone

I agree. It is a bit of a mystery. My random guess is that the power at rail can be temporarily higher by 10-15% above the continuous rating of the motors when starting up and such. Another random guess is that with the sort of HEP loads you'd have in a typical SC-44 powered Midwestern train, HEP loads would be realtively low. Things could very different if a train that actually pulled 1MW HEP like the Auto Train, was being powered. But as I said, consider these me just thinking aloud.

I don't know anyone in the Midwest, but I do know the operations guys at Brightline. Maybe I will ask them when I see them again at the introduction of Commercial Service to Orlando International Airport in the near future and see fi they can shed any light on this. Of course they have the derated SCB-40, which they clami would be more reliable and last longer with the power derating. And their claim the last time I talked to them was that it is the prime mover output that is derated.



Edited 2 time(s). Last edit at 04/24/23 09:21 by Jishnu.

Isn't all this stuff computer monitored and controlled? Wouldn't it be the software that determines the power output? Within equipment limitations of course.

2904 Wrote:
---------------------
> Horsepower to rails regardless of producing HEP:
>
>
> SC44 - 4400
> ALC42 - 4200

Horsepower toward the rails, you mean.
Can't expect 4400 hp to reach the wheel rims
if us Americans call it a 4400 hp locomotive.

So you are saying the SC44 is supposed to
produce 4400 hp for traction even on a
train that is demanding 500 kW of HEP?
The diesel is good for 5000+ hp total?

I talked to 3 people on this matter - everyone says they DO NOT derate and lose HP from HEP and maintain full power to the motors. Brightline, Amtrak, and Coaster. No stretch braking though, which sucks.

Whatever voodoo they have going on, works. 

They do allow stretch braking, for a matter of a millisecond above 20 mph, and for 30 ish seconds below 20 mph. The ALC42s have a 3 minute timer that will knock out power regardless of speed after the time elapsed. They have their quirks but when they work they do get down and dirty quick… and their blended brake is superior to any other passenger engines I’ve run, F40s to P42s, etc. One thing that is for sure is they do not derate horsepower for HEP ever. But from reading the SC44 and ALC42 manuals today since this has been a hot topic, the traction motors are indeed rated for 950ish HP a piece, which means an ALC42 and SC44 only put out 3960 or so horsepower..: even though both manuals say they can produce 4200 horsepower of tractive effort continuously and 4400 max. So who knows if they is even accurate at this point. I give up haha

Posted from iPhone



Edited 1 time(s). Last edit at 04/24/23 14:12 by 2904.

Back in the 90s I was on a trip on the southbound Starlight with two Dash 8s and one died leaving Eugene.  They cut HEP off briefly climbing over the Cascades, but the remaining locomotive was able to handle the train the rest of the way into Oakland. At Oakland they put an F40 on for the the trip to Los Angeles.

Todd Clark
Canyon Country, CA
Trainorders.com

2904 Wrote:
-------------------------------------------------------
> They do allow stretch braking, for a matter of a
> millisecond above 20 mph, and for 30 ish seconds
> below 20 mph. The ALC42s have a 3 minute timer
> that will knock out power regardless of speed
> after the time elapsed. They have their quirks
> but when they work they do get down and dirty
> quick… and their blended brake is superior to
> any other passenger engines I’ve run, F40s to
> P42s, etc. One thing that is for sure is they do
> not derate horsepower for HEP ever. But from
> reading the SC44 and ALC42 manuals today since
> this has been a hot topic, the traction motors are
> indeed rated for 950ish HP a piece, which means an
> ALC42 and SC44 only put out 3960 or so
> horsepower..: even though both manuals say they
> can produce 4200 horsepower of tractive effort
> continuously and 4400 max. So who knows if they
> is even accurate at this point. I give up haha
>
> Posted from iPhone

Thanks for the clarification! That makes sense in some ways and adds even more questions