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DC Traction Motor Ratings - Continuous vs. Short-Time - in Amps/ HP, etc.

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DC Traction Motor Ratings - Continuous vs. Short-Time - in Amps/ HP, etc.
Posted by Paul_D_North_Jr on Tuesday, December 01, 2009 11:20 AM

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.

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Posted by timz on Tuesday, December 01, 2009 4:56 PM

Scroll down to the pic near the bottom of

http://krugtales.50megs.com/rrpictale/p030224/p030224.htm

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Posted by Paul_D_North_Jr on Tuesday, December 01, 2009 5:31 PM

Aha !  Thank you ! Bow 

Never would have found that otherwise.  I owe you one sometime, timz.

- Paul North.

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Posted by Paul_D_North_Jr on Wednesday, December 02, 2009 5:36 AM

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.

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Posted by blue streak 1 on Wednesday, December 02, 2009 6:19 AM

Paul_D_North_Jr
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

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?

 

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Posted by Paul_D_North_Jr on Wednesday, December 02, 2009 8:06 AM

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;

- Did whoever assigned the power that day think about this at all ?  What if it had been a hot summer day, and the B40 couldn't sustain the load for the entire time with the warmer ambient cooling air ?

- 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 North.

P.S. - The B40-8 has GE 752AH traction motors, per information from the ConRail Historical Society. - PDN. 
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Posted by beaulieu on Wednesday, December 02, 2009 8:58 AM
9 miles from Ranchester to Parkman, the top of the hill, 35 minutes to climb it. That means his average speed was 15.4 mph. He probably had some speed going into the grade so that his speed after the first few minutes would be lower. Good thing his B40-8 has MTP (Motor Thermal Protection) which means that he could let the computer worry about how hot the traction motors were. At that speed the SD40-2 would not be in its Red Zone.
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Posted by timz on Wednesday, December 02, 2009 12:44 PM

Paul_D_North_Jr
Could 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.

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Posted by oltmannd on Wednesday, December 02, 2009 1:16 PM
timz

Paul_D_North_Jr
Could 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.
I think you are right. Amps are roughly proportional to TE and volts to speed, so, lower amps = lower TE. BTW, the early SD50s had a motor temp simulator (MS module) that featured a block of copper (I think) heated by current proportional to that in the TMs and cooled by air piped in from the TM blower duct. No kidding!

-Don (Random stuff, mostly about trains - what else? http://blerfblog.blogspot.com/

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Posted by Paul_D_North_Jr on Wednesday, December 02, 2009 2:01 PM

 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.

- Paul North. 

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Posted by beaulieu on Wednesday, December 02, 2009 2:21 PM

timz

Paul_D_North_Jr
Could 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.

 

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.

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Posted by Paul_D_North_Jr on Wednesday, December 02, 2009 4:29 PM

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 

Al Krug's 
Tractive Effort
EMD
Tractive Effort
Amps
136297* 97200 1200
95407* 82800 1050
63605 60480 850
47704 48300 720
38162 37800 600
31802 34800 550
27259 26400 480
21202 22920 395
19081 19200 365

*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 North.

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Posted by JayPotter on Wednesday, December 02, 2009 8:19 PM

Paul_D_North_Jr
I 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.

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Posted by tree68 on Wednesday, December 02, 2009 9:46 PM

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.

On the other hand, an article about AC traction (I think it was in Trains) indicated that an AC locomotive could run as slow as 1/2 MPH in Run 8.

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...

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Posted by Paul_D_North_Jr on Saturday, December 05, 2009 5:24 AM

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.

- Paul North.

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.

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Posted by timz on Saturday, December 05, 2009 12:36 PM

Paul_D_North_Jr
But since he was probably running in full series

Road locomotives never run in full series, and never have. It's a safe bet all the Dash-8s kept their traction motors in parallel; if they used any transition, it would have been in the generator/alternator.
Paul_D_North_Jr
 600 volts (nominal)
That's a familiar phrase, but no idea where it originated. No reason to assume the GE's generator/alternator was producing that voltage at the time.

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Posted by oltmannd on Saturday, December 05, 2009 4:45 PM
Paul_D_North_Jr

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 -

All four axle locomotives from GE and EMD post Dash 2 and Dash 7 are full time parallel machines. The six axles of the Dash 8 and 50 series (and newer) have transition, but it's generator transition. The generator voltage varies with speed. At low speeds, low votlage! The trouble is the high end...

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Posted by erikem on Sunday, December 06, 2009 2:35 PM

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

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Posted by beaulieu on Monday, December 07, 2009 8:54 AM

Paul_D_North_Jr

I 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

 

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Posted by Paul_D_North_Jr on Monday, December 07, 2009 9:33 AM

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 )

Take the seats out of a railcar and what do you have? A locomotive
Trains, December 1973 page 40
How it all began
( "CORLEY, RAYMOND F.", FREIGHT, GAS-ELECTRIC, GE, "HAMLEY, DAVID H.", LOCOMOTIVE, 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 North.

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Posted by erikem on Monday, December 07, 2009 8:51 PM

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.

- Erik

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Posted by favuprailroadfan on Friday, February 19, 2010 10:19 PM

 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

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Posted by Paul_D_North_Jr on Wednesday, April 27, 2011 11:46 AM

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 

- Paul North. 

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Posted by daveklepper on Sunday, May 01, 2011 7:40 AM

Gee, when I tested locomotives on the B&M in 1952-1923, EMD had the very best reputation possible!

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