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  • Amtrak F40PH head end power questions

  • Discussion related to Amtrak also known as the National Railroad Passenger Corp.
Discussion related to Amtrak also known as the National Railroad Passenger Corp.

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 #886829  by rckingsnorth
 
Regarding the following techie questions, any information or referrals to others is much appreciated.

Amtrak’s F40PH ran continuously at notch 8 to drive the head end power for passenger cars. “The Contemporary Diesel Spotter’s Guide” (second edition) states that when run in multiple, only one can furnish head-end power. Does the second unit also run continuously at notch 8?

Also, what are the characteristics of Amtrak’s GE Dash 8-32BWH? Does it run at notch 8 for head-end power? And if run in a consist with an F40PH, what are the notch setting for each?

And what are the notch (HEP) characteristics of the P40 and P42?

Many thanks!
 #886934  by timz
 
If the train has two units, one supplies HEP and the other responds to the throttle in the traditional way-- i.e. 315 RPM or whatever it is at Idle. Which means the second unit will probably be the one supplying HEP, giving the engineer a quieter ride.

P32s-P40s-P42s don't have a separate HEP diesel so their prime movers have to stay at constant speed to produce HEP at a constant AC frequency. NJT's PL42s and LIRR's diesels have AC traction motors, so they have inverters, so they can get their HEP from an inverter, so their 710s don't have to run at constant speed.
 #887060  by DutchRailnut
 
The P32acdm does not run at constant RPM they run from 630 Rpm to 1047 RPM while providing HEP.
their HEP is inverter fed from a DC link which is fed by traction alternator.
 #887094  by timz
 
No doubt DRN is right about the third-rail GEs-- but probably all of Amtrak's diesel-only diesels have to run their FDLs at constant speed when supplying HEP?

(And they don't run at 1050 RPM, do they? What is it, 900, or 960, or what?)
 #887102  by Jtgshu
 
timz wrote:No doubt DRN is right about the third-rail GEs-- but probably all of Amtrak's diesel-only diesels have to run their FDLs at constant speed when supplying HEP?

(And they don't run at 1050 RPM, do they? What is it, 900, or 960, or what?)
Its been a while since I ran a P40, but IIRC, it is somewhere around 1050 rpms or so when providing HEP.

The F40s would run in Notch 8 when they were providing HEP, which is about 905rpms. some commuter railroads stil run "screamer" F40s, where HEP is still provided by the prime mover running in Notch 8, others have had additional smaller HEP motors installed, and the diesel prime mover runs at regular RPMs, while the seperate diesel engine, a Caterpillar, or Cummins or whatever engine woudl provide HEP to the train.

A PL42 has its HEP provided by an inverter poewred from the prime mover, and when a PL42 is providing HEP, it is running in Notch 3, which is about 450rpms.
 #887130  by EricL
 
The whole "notch"' notion of fixed-RPM-for-HEP locomotives is a bit of a misnomer. It is not as if the engineer on an F40 literally has to leave the throttle handle in 8, only opening the Generator Field switch when he wants to move. Rather, these fixed HEP RPM locomotives are fitted with appropriate governors or computers to keep the diesel engine itself constantly running at the appropriate speed. (This model includes the GE Genesis series.) Tractive power is still controlled by the engineer's throttle handle, but it only controls electrical input to the traction motors, in such a case. Such power is referred to as "excitation" in the operating and troubleshooting manuals.

"Constant RPM HEP"' and '''non constant HEP" locos are compatible in a M.U. configuration for just this reason. The engine supplying the HEP - whether by separate alternator or separate engine PLUS alternator - will adjust its tractive effort automatically, according to the throttle position commanded thru the trainline by the lead unit. Similarly, non-HEP-supplying units in consist will simply act as if HEP doesn't even exist, and will respond directly to trainline throttle calls. Non HEP supplying units will naturally develop higher horsepower and traction amps than the HEP supplying unit, but the difference is small enough to avoid undesirable wheel slide, slack action, etc.

There are two arguments for keeping the HEP on the head end of a multiple unit consist. One - the HEP startup/shutdown controls are readily accessible to the engineer. Two, the engine producing HEP will naturally produce slightly less H.P. than the others, and thus is at less risk for wheel slip. Wheel slide only really matters on the lead unit, since when the first wheelset traverses wet rail (whether with sand on or off), it tends to "clean" the rails off, to a certain extent, for the trailing vehicles.

The disadvantage, as mentioned earlier, is the notable increase in cab noise. And as far as the P42s go - while a solid P42 consist should theoretically perform about the same no matter where the HEP is, there does seem to be a noticeable difference in acceleration capability when HEP is on a trailing unit. Don't ask me how that works.

The only real notation to be made here is that, in single unit operation, a locomotive with prime-mover-powered HEP cannot be moved while HEP is in "standby" mode. This is because the HEP electrical load is thus shifted to the Traction Alternator, which is normally reserved for tractive movement. In this mode, the diesel engine is also reduced to a lower RPM (somewhere in the 500-600 range), to provide for lower fuel consumption and emissions. In some terminals, complete shutdown of engine HEP, in favor of ground power, is standard. It is only with ground power that single-unit prime-mover-powered-HEP trains can truly shift into "low idle" mode, apart from HEP being shut down completely.

edit: for reference: P42 with Normal HEP is 900 rpm engine, while engine without HEP load goes almost 1100 rpm. A well-maintained P42 can pull a seven car set with HEP with about 1200 traction amps max, while with no HEP it would be somewhere in the neighborhood of 1500 amps.

To directly answer the OP's question, only one source can supply 480v power, no matter what. Even if a train has 8 locomotives, only one can supply HEP. If ground power is hooked up to the train, then no locomotive will be able to supply HEP, until the ground power is unplugged. This begs the question - how long can passenger trains be? Normally, at Amtrak, they do not exceed 15 cars, to avoid exceeding the limits of the single-source-HEP model.
 #887150  by DutchRailnut
 
Jtgshu wrote:Its been a while since I ran a P40, but IIRC, it is somewhere around 1050 rpms or so when providing HEP.
The P40 in HEP mode runs at 900 rpm and therefor reduces total engine horsepower from 4200 to about 3750 hp while providing HEP.
 #887164  by AMTK1007
 
Very well written and described Mr. L. It should be noted that "WAY BACK IN THE DAY" the original GE's, the P30s were indeed able to sync the HEP generators on multiple units and thus supply HEP from more then one unit. I believe that is one reason those behemoths were assigned to the Auto train.

As for your question regarding the effective maximum legnth of a train in regards to HEP, as I understand it, the limit is somewhere around 18-20 cars ( based on the Amtrak single bus HEP system). I believe that is what the "Everywhere West Train, the combined Cal Z/Desert Wind/Pioneer topped out at. This was based on 2 things, HEP generator size and the resistance on the HEP trainlines as train legnth and electrical use increases. While the draw may not be too bad in April, the draw can be significant in Jume with all the AC units running ( or December with all the heaters running). I recall a time in Chicago when they brought 7 down from the yard. It had been off power for some time so that the cars were cold inside, but had not frozen ( I believe this was in the run through days and they did switching to cut off some of the Portland cars and replaced a bad order or 2). When they plugged the train in to ground power, the ground power kept triping the circuit breakers (at about 1800 AMPS) due to the draw of all the heaters. They solved the problem by switching off 1/2 the heaters in each car until the draw came down.
EricL wrote:The whole "notch"' notion of fixed-RPM-for-HEP locomotives is a bit of a misnomer. It is not as if the engineer on an F40 literally has to leave the throttle handle in 8, only opening the Generator Field switch when he wants to move. Rather, these fixed HEP RPM locomotives are fitted with appropriate governors or computers to keep the diesel engine itself constantly running at the appropriate speed. (This model includes the GE Genesis series.) Tractive power is still controlled by the engineer's throttle handle, but it only controls electrical input to the traction motors, in such a case. Such power is referred to as "excitation" in the operating and troubleshooting manuals.

"Constant RPM HEP"' and '''non constant HEP" locos are compatible in a M.U. configuration for just this reason. The engine supplying the HEP - whether by separate alternator or separate engine PLUS alternator - will adjust its tractive effort automatically, according to the throttle position commanded thru the trainline by the lead unit. Similarly, non-HEP-supplying units in consist will simply act as if HEP doesn't even exist, and will respond directly to trainline throttle calls. Non HEP supplying units will naturally develop higher horsepower and traction amps than the HEP supplying unit, but the difference is small enough to avoid undesirable wheel slide, slack action, etc.

There are two arguments for keeping the HEP on the head end of a multiple unit consist. One - the HEP startup/shutdown controls are readily accessible to the engineer. Two, the engine producing HEP will naturally produce slightly less H.P. than the others, and thus is at less risk for wheel slip. Wheel slide only really matters on the lead unit, since when the first wheelset traverses wet rail (whether with sand on or off), it tends to "clean" the rails off, to a certain extent, for the trailing vehicles.

The disadvantage, as mentioned earlier, is the notable increase in cab noise. And as far as the P42s go - while a solid P42 consist should theoretically perform about the same no matter where the HEP is, there does seem to be a noticeable difference in acceleration capability when HEP is on a trailing unit. Don't ask me how that works.

The only real notation to be made here is that, in single unit operation, a locomotive with prime-mover-powered HEP cannot be moved while HEP is in "standby" mode. This is because the HEP electrical load is thus shifted to the Traction Alternator, which is normally reserved for tractive movement. In this mode, the diesel engine is also reduced to a lower RPM (somewhere in the 500-600 range), to provide for lower fuel consumption and emissions. In some terminals, complete shutdown of engine HEP, in favor of ground power, is standard. It is only with ground power that single-unit prime-mover-powered-HEP trains can truly shift into "low idle" mode, apart from HEP being shut down completely.

edit: for reference: P42 with Normal HEP is 900 rpm engine, while engine without HEP load goes almost 1100 rpm. A well-maintained P42 can pull a seven car set with HEP with about 1200 traction amps max, while with no HEP it would be somewhere in the neighborhood of 1500 amps.

To directly answer the OP's question, only one source can supply 480v power, no matter what. Even if a train has 8 locomotives, only one can supply HEP. If ground power is hooked up to the train, then no locomotive will be able to supply HEP, until the ground power is unplugged. This begs the question - how long can passenger trains be? Normally, at Amtrak, they do not exceed 15 cars, to avoid exceeding the limits of the single-source-HEP model.
 #887227  by slchub
 
I know there were times when we had the Grand Luxe out of Salt Lake City and that bad boy had 20+ cars on it with a P42 providing HEP. How she managed to do it, I have no idea.
 #888812  by DutchRailnut
 
There is no specific car limit, a Genesis has a 800 Kw HEP unit which is good for aproximatly 20 to 26 superliners depending on what season it is.
Summer and winter draw a heck of lot more than spring and fall ;-)
 #896318  by Stmtrolleyguy
 
DutchRailnut wrote:There is no specific car limit, a Genesis has a 800 Kw HEP unit which is good for aproximatly 20 to 26 superliners depending on what season it is.
Summer and winter draw a heck of lot more than spring and fall ;-)
That wouldn't leave a whole lot of horsepower free for getting the train moving, right?
I'm assuming the higher the HEP load, the lower the load the engine can put towards providing traction power.
 #896320  by DutchRailnut
 
at full 800 Kw (approx. 1000 HP) the engine still has 2850 HP for traction since in HEP mode a Genesis is max 3850 hp at 900 rpm, second engine would have full 4200 at full 1047 rpm.
 #896413  by slchub
 
DutchRailnut wrote:at full 800 Kw (approx. 1000 HP) the engine still has 2850 HP for traction since in HEP mode a Genesis is max 3850 hp at 900 rpm, second engine would have full 4200 at full 1047 rpm.
Agree. Most trains with two units will have the HEP on the trailing motor as the crew gets tired of listening to the motor running at full RPM for hours on end, plus the vibration gets old as well. Two motors on the California Zephyr is plenty of power even heading up and over several mountain passes between Emeryville and Chicago. On one station stop (Helper, Utah) as we head west we are stopped on the grade and accelerate to 30 MPH for the climb up to Soldier Summit and get her up to speed within 3/4 of a mile (2 P-42 motors, bag car and 8-9 cars). No issue with the HEP taking away from full HP potential.
 #897514  by rckingsnorth
 
My thanks to everyone for pitching in.

I will try to summarize the comments. I am still in the leaning mode, so please correct me as needed.

For all models, one and only one unit can provide HEP – because current units cannot synchronize multiple 60 Hz sources (But the old P30’s apparently had that capability.)

Any additional units (non-HEP) will operate at varying rpm in response to the engineer’s throttle setting, independent of HEP unit.

The Amtrak F40PH, as originally built, must run at max rpm (about 905 rpm) to generate HEP.

Your comments suggest that all the Amtrak GE locomotives also run at a constant (?) rpm for HEP:
P32 (Dash8-32BWH – 12 cylinders) – xxx rpm (?)
P40/P42 (16 cylinders) – 900 rpm (?)

The engineer’s throttle controls the variable power/amps to the traction motors while a regulator/computer maintains a constant rpm for HEP requirements.

When multiple units are used, is it the crew’s option which unit provides HEP? Crew comfort/fatigue would seem to be an important consideration.

Other users - NJY and LIRR (these are AC units) - drive the HEP through inverters, so constant rpm is not a requirement. A PL42 can run at 450 rpm (notch 3) for HEP alone. Any additional rpm provides power to the traction motors. Also, if using ground power, the on-board HEP unit is shut down and the diesel is at idle.

Comments, corrections?

Thanks!