I've been looking for a while for information on the above - both 'on-line' and at a recent local train show - but haven't had much luck in in my search, so I thought I'd try to tap the expertise here. I've already done a 'Search Community' for ''ratings'' and found lots of useful and interesting information and discussion and debates - such as the ''AEM-7 vs. GG1'' thread - but not this specific type of data. Generally, I know that these ratings are governed by limiting the motor winding heating to what they can stand with the blowers running - hence the continuous rating is at one level, the 1-hour rating a little higher, and the 15-minute and 5-minute ratings each a little higher than the last - maybe 5 or 10 percent, but not double, and so on.
What I'm specifically looking for is a set of numbers for those durations for a specific traction motor type, so that I can better understand the quantitative relationships between them. Any one will do - as a most common example, I'll suggest the D77 traction motor as used under the EMD SD40-2 model locomotives - but if someone has the data or a table on some other EMD or GE motor that would be fine as well. I'm not sure if this can be found in the manufacturer's operating manuals, on the gauges in the cab, both places or someplace else, etc. Alternatively, if you can point me to a link or reference with that information, I will appreciate that, too.
Thanks in advance for any help you can provide.
- Paul North.
Scroll down to the pic near the bottom of
http://krugtales.50megs.com/rrpictale/p030224/p030224.htm
Aha ! Thank you !
Never would have found that otherwise. I owe you one sometime, timz.
It's an installment of "Tales From The Krug" dated February 24, 2003, and the segment at the bottom is titled "Darn Hard Pull". The photo is of a GE B40-8's ammeter, and here are the values for the markings as best as I can interpolate them:
03 Dec. 2009 - Thurs. 2:45 PM EDIT: Add % below.
Continuous = end of Green / start of Red zone: 1300 Amps = 100 %
60 minutes: 1340 Amps = 103 %
30 minutes: 1360 Amps = 104.6 %
15 minutes: 1400 Amps = 107.7 %
5 minutes: 1500 Amps = 115.4 %
So no - you don't normally get too long in that red zone. If the situation is short enough and only a little more power is needed, this might provide enough of a boost to make it. But it's not enough extra to get over a long hard hill in half the time by going twice as fast = twice the amps, for example.
Next: I need to find out what model traction motors are on the B40-8's?
By the way - Al Krug's photo shows the meter nearly pegged' at 1675 Amps, and he says it was there for 35 minutes. How was he able to do that ? Well, the outside air temperature was only +2 degrees F, so the traction motor cooling blowers were unusually effective that morning.
Paul_D_North_JrBy the way - Al Krug's photo shows the meter nearly pegged' at 1675 Amps, and he says it was there for 35 minutes. How was he able to do that ? Well, the outside air temperature was only +2 degrees F, so the traction motor cooling blowers were unusually effective that morning
You bring up an interesting question. The traction motor cooling curves would be subject to the ambient temperature and absolute atmospheric pressure. Has anyone ever come across those graphs? And at what temp and pressure are the red zone numbers posted on the ampmeter?
Some other points from Al Krug's article:
- The B40-8 had about 1,000 HP per axle - 4,000 HP / 2 'B' trucks;
- The trailing SD40-2 had only about 500 HP per axle - 3,000 HP / 2 'C' trucks;
- That's why the SD40-2 was able to keep going with no loss of power - it was at about half the amps of the 4-motor GE;
- The train had a power/ weight ratio of almost 1.5 HP/ ton, and was going up Parkman Hill. Krug has written about it several times;
- I wonder how fast he was going ? Could they have gotten up almost as well with a lower amperage = same tractive effort, but less speed ?
Paul_D_North_JrCould they have gotten up almost as well with a lower amperage = same tractive effort, but less speed ?
timzPaul_D_North_JrCould they have gotten up almost as well with a lower amperage = same tractive effort, but less speed ?I never have understood the relationship between amps/volts/speed/TE, but I'm guessing lower amps at lower speed means lower TE.
-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/)
Thanks much to everyone who has contributed to this thread so far. It appears that I too didn't quite throughly understand the relationship between those electrical values and HP and TE. However, recalling the tri-power 'Kiddie Car' article* in Trains some years ago, the author wrote that he was told by someone from the GE home office - Eric somebody, I believe: ''To hell mit der volts - it's der amps vot count !'' Put very simply - volts are proportionately related to/ cause 'speed' and HP, but amps are what create the tractive effort force.
*EDIT-2: Ohms vs. Ms Trains, July 1971 page 44 tripower locomotives on the Lackawanna ( "CRATON, FORMAN H.", DIESEL, DL&W, TRIPOWER, ENGINE, LOCOMOTIVE, TRN )
Anyway, here's a link to another good close-up photo of a readable ammeter or 'amp meter' on one of the former Erie Mining Co. EMD F9A's - No. 4211 - at Hoyt Lakes, Minnesota. EDIT-1: The F9A was rated at 1750 HP, and had 4 ea. D37 traction motors, per - http://www.thedieselshop.us/Data%20EMD%20F9.HTML
http://www.rrpicturearchives.net/showPicture.aspx?id=748395
It also has a very faded table or list or 'schedule' of allowable amps on a plate or badge mounted underneath it, as follows:
SHORT TIME RATING
NON-ACCUMULATIVE
Continuous - 900 Amp.
1 Hour - - 925 Amp.
1/2 Hour - 970 Amp.
1/4 Hour - 1065 Amp.
10 Minutes - 1140 Amp.
5 Minutes - 1275 Amp.
It is due to the effect of Lenz's Law. The power formula changes from W = A * V to W = A* (V-I) where "I" is the Inductance. With a DC series wound motor the Inductance is directly proportional to the rotational speed if the motor field strength is constant. Halve the rotational speed, then you halve the Inductance. Since you are trying to maintain constant power at the motor the effective voltage in the motor circuit increases as the motor's rotational speed decreases, and because of Ohm's Law you have to reduce supplied voltage from the main generator to maintain a constant power. And yes the the type of Inductance found in a motor circuit is frequently referred to as Back EMF.
Here's chart for the Tractive Effort and amps of an SD40 from Al Krug's website, specifically the ''Railroad Facts and Figures'', ''Amperage to Tractive Effort table for an SD40-2'', under the heading ''My Tractive Effort vs EMD's'' at - http://www.alkrug.vcn.com/rrfacts/amps_te.htm
*The two lowest speed values, 7 mph & 10 mph, may bit a bit high on the estimated TE account I assume the loco is putting out its full rated 3,000 Hp. But in reality the output is probably reduced a bit account of wheelslip control at those speeds.
The accompnanying article is highly recommended reading, if a bit technical.
On another page -''Tractive Effort vs Horsepower'', at http://www.alkrug.vcn.com/rrfacts/hp_te.htm - he has this to say:
HP is the Tractive Effort (pull) times the Speed.Burn that statement into your brain. It is crucial to understanding this essay.
Horsepower is Speed.[snip] Note that Hp is TE times speed. If the speed remains the same and the TE (pull) increases then the Hp requirement increases. If the TE remains the same and the speed increases then the Hp requirement increases. If you have a fixed maximum Hp, such as a loco has, then as speed increases the TE must come down. The product of the two must remain a constant and is directly related to the HP rating of the loco.
I haven't found anything else other than beaulieu's explanation above of how voltage interacts with speed, and hence amps and tractive effort.
Incidentally, Krug says that thesubject Parkman Hill on the former CB&Q - at 25 miles west of Sheridan, Wyoming - is a 1.25 % grade both EB and WB - see his chart of ''Major Railroad Grades'' at http://www.alkrug.vcn.com/rrfacts/grades.htm
He also seems to imply that Parkman Hill is about 24 miles long per the following, from - http://www.alkrug.vcn.com/rrfacts/hp_te.htm
One mph is kind of slow. It would take us 24 hours just to get up Parkman hill.
If that is the case, then his average speed must have been aroubnd 40 MPH - and as a result, the amperage would have dropped below the Red Zone. But I think beaulieu's data and calcs - esp. the 15.4 MPH average speed - fits this scenario much better.
EDIT: I suppose it depends on which way he was climbing the hill. At the following link is a Map, Timetable, and Profile of the Bighorn Subdividsion:
http://krugtales.50megs.com/rrpictale/map/map.htm
From reviewing the profile, it appears that the Westward grade is 1.25 %, from Ranchester at MP 715 to Parkman summit at MP 724 = 9 miles; going the other way, Eastward, the maximum grade appears to be 1.30 % from Aberdeen at MP 732 to Parkman summit at MP 724 = 8 miles. However, from the data in the Timetable it appears that there is about a preceding 1.0 % grade from Wyola at MP 737 to Aberdeen at MP 732 = 5 more miles, even though on the profile it is marked as only a 0.80 % grade. But with even that added, it's still only 13 miles overall - not 24 miles. [End Edit]
Thanks again for everyone's input and insights.
Paul_D_North_JrI haven't found anything else other than beaulieu's explanation above of how voltage interacts with speed, and hence amps and tractive effort.
I recommend the book Diesel-Electric Locomotive Handbook - Electrical Equipment by George F. McGowan. It was published in 1951; and it contains more detailed discussions of basic electrical concepts than I've found in more recent publications.
Paul_D_North_Jr He also seems to imply that Parkman Hill is about 24 miles long per the following, from - http://www.alkrug.vcn.com/rrfacts/hp_te.htm One mph is kind of slow. It would take us 24 hours just to get up Parkman hill.
Now Parkman Hill would require three recrews (not to mention the initial crew) to make the trip. Getting on and off the loco at that speed wouldn't exactly be a challenge...
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
I'm wondering what the HP output of Krug's B40-8 was that morning.
If the 1300 Amp Red Zone rating is for full parallel - not likely for a low speed - that would be:
600 volts (nominal) x 1300 amps rated = 780,000 watts = 780 KW
Divide by 0.746 KW per HP = 1,045 HP per motor x 4 = 4,180 HP for the whole unit.
OK, that makes sense so far.
But since he was probably running in full series instead due to the low speed, it would only be 1/4 of that nominal voltage, or 150 volts, since it was spread across all 4 motors - hence, about 261 HP per motor, or 1,045 HP for the entire unit.
But since the actual amperage was 1,675, the motors and unit were putting out more than that. By proportions, about 337 HP per motor, or 1,350 HP for the whole unit.
Of course, the actual voltage was probably somewhat higher, since the engine and generator were not likely loaded to the max.
What's interesting to ponder - and why I posted the original question - is what if that had been a straight electric locomotive instead, with the unlimited catenary supply. Then potentially each motor could have had the 600 volts at 1,675 amps = 1,005 KW / 0.746 = 1,350 HP per motor, or 5,400 HP for the entire unit = a 35 % increase, very temporarily. In actual day-to-day operation, the cold weather of that morning can't be counted on to occur, of course, so the potential short-term power boost is more in line with the percentage increases that I posted alongside the ammeter markings above. Still, it's interesting to think about.
EDIT: Here's the link to an interesting webpage from a traction motor manufacturer and repair shop:
http://www.swigercoil.com/dc-motor-repairs-process.asp
- PDN.
Paul_D_North_JrBut since he was probably running in full series
Paul_D_North_Jr 600 volts (nominal)
Paul_D_North_JrI'm wondering what the HP output of Krug's B40-8 was that morning. If the 1300 Amp Red Zone rating is for full parallel - not likely for a low speed -
If the 1300 Amp Red Zone rating is for full parallel - not likely for a low speed -
Paul_D_North_Jr Thanks much to everyone who has contributed to this thread so far. It appears that I too didn't quite throughly understand the relationship between those electrical values and HP and TE. However, recalling the tri-power 'Kiddie Car' article* in Trains some years ago, the author wrote that he was told by someone from the GE home office - Eric somebody, I believe: ''To hell mit der volts - it's der amps vot count !'' Put very simply - volts are proportionately related to/ cause 'speed' and HP, but amps are what create the tractive effort force.
Might well have been me, the quote is from Hermann Lemp who invented the three winding traction generator excitation design. Trains did carry an article on the Lemp system in the late 70's - thinking it might have been early 1979.
- Erik
Paul_D_North_JrI haven't found anything else other than beaulieu's explanation above of how voltage interacts with speed, and hence amps and tractive effort. - Paul North.
Here are a few links to the relevant formulae
Faraday's Law of Inductance
Faraday's Paradox
Lenz's Law
I was trying to remember that article, too - I'm thinking it might have been in the last article of the 3 in this series:
About the railcars which (unintentionally) forecast dieseldom Trains, November 1973 page 36 How it all began ( "CORLEY, RAYMOND F.", GAS-ELECTRIC, GE, "HAMLEY, DAVID H.", RAILCAR, ROSTER, TRN )
How to control and engine of limited power Trains, January 1974 page 26 How it all began ( CONTROL, "CORLEY, RAYMOND F.", DIESEL, GAS-ELECTRIC, GE, "HAMLEY, DAVID H.", ENGINE, LOCOMOTIVE, TRN )
I didn't find anything in the 1979 time frame that looked to be pertinent.
Paul_D_North_Jr How to control and engine of limited power Trains, January 1974 page 26 How it all began ( CONTROL, "CORLEY, RAYMOND F.", DIESEL, GAS-ELECTRIC, GE, "HAMLEY, DAVID H.", ENGINE, LOCOMOTIVE, TRN )
That's most likely the one.
Take a GP30, tear it apart, rebuild the 567 motor, keep the GE traction motors and ALCO trucks. Put DASH2 electricals in, give it a gp 35 look. What do you have? The only 2 GP26's ever built. The combo of EMD power and electricals and GE traction motors geared at 74:18 makes for a very nice pulling combo. These 4 axle locomotives will do 1500-1600 amps for at least 10 minutes and not overheat or quit working. This is in nice weather, not cold. I do operate these locos on the Cimarron Valley Railroad in SW KS. I ran them both today. These 2 can take 50 loads up a 2.2 percent grade. Granted it would be at a slow speed, around 5 mph. But thats when they really get down to business. I don't know any tractive effort on them. But I can tell you they weigh 278,000 pounds. They are rated at 2250 hp but personally I think they are 2500. They were rebuilt by Paducah in 1981. If you guys have any questions. Hit me up. Later, Dru. Engineer. CVR
Found another great Al Krug photo of an ammeter/ "Load Meter" with the short-time rating markings clearly visible - "GP60M Cab Study" dated March 21, 2000 (or as I would have captioned it - "Why I Hate GP60M's and their 'Desktop' Controls"):
http://krugtales.50megs.com/rrpictale/GP60/GP60a.htm
Gee, when I tested locomotives on the B&M in 1952-1923, EMD had the very best reputation possible!
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