Greetings,

I am searching for amp ratings for GP30s equipped with D57 traction motors. This is what I've found for an E8 (different traction motors)/what I'm after for the D57 (EMD owner's manual doesn't have), which is attached. I've also found this for F9:
Traction motor: D37
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.


Thanks in advance for any help.

Have you tried Progress Rail? They sell reconditioned parts/assemblies and may have documentation for the D57 motors.

Hi Eric,

Thanks for the tip! Since I had found other ratings via Google searches, I was hoping someone could steer me in the right (online) direction, know it off the top of their head, etc...but failing that, indeed I can contact Progress Rail.


Thanks again,

John

For whatever reason, the Publications Manager missed including the short time ratings in the GP30 Operators Manuals that I have seen. They are listed below for a GP30 with D57 motors:

Continuous - 980 Amps
1 Hour - 1000 Amps
1/2 Hour - 1025 Amps
1/4 Hour - 1075 Amps

Reference: Table HFR dated 3-28-68; based on ERC-922

Correct ammeter for the GP30 is EMD P/N 8214188

Reference: Catalog 190, List C4331, Column "A", Page 2, Item 72

PC

Preston-thank you, sir!
You illustrate the best aspects of rypn. Your knowledge and contributions are greatly appreciated.

Thanks, John. Several people I worked with at EMD shared their technical information with me, and I have organized and am transferring those collections to the Barriger Library. Hopefully that will preserve some useful information on heritage EMD products into the future, along with the Winton, Alco, GE, FM, BLH, Budd and Detroit Diesel information that I was able to save.

PC

Hi (again) Preston!

I'm hoping to draw upon your knowledge once again. Same topic, relates now to train handling, but still about amp ratings.
Scenario-I'm a licensed diesel locomotive engineer. I was running an E8 for the first time, approaching a stop. Mention was made that I was drawing 400 amps. Others have since said that's no big deal.

When 'short-term' D57 ratings are 1/2 Hour - 1025 Amps and 1/4 Hour - 1075 Amps, and D37 are 970 and 1065 for the same periods of time-what is the issue about drawing 400 amps? If I'm understanding correctly, I could be running 650 amps as I slow to a stop (say 2 minutes, max), and it's within ratings.

Thanks in advance for your thoughts on this.

Sorry for the delay getting to this question, I have several magazine publication projects running simultaneously and am trying to keep up.

The short time rating information for any particular locomotive is applicable only at throttle eight. This is because the rating is based on having maximum cooling air flow through the traction motors. The typical explanation from an EMD operator’s manual is as follows:

SHORT TIME RATINGS
The maximum continuous current rating of the traction motors and the value given on the traction motor short time rating plate is applicable only when operating at throttle No.8 engine speed. These values decrease as engine speed and cooling air is decreased.


Regarding the question on braking while operating with power, the ammeter reading in a throttle notch will increase as the speed of the locomotive decreases. This is because the locomotive generates a constant horsepower in each throttle notch. Conversely, at a low speed in a particular notch you are generating a lot of amps, as your speed increases the amperage drops off, but you are still producing the same horsepower. Here is the applicable operators manual instruction:

AIR BRAKING WITH POWER
The method of handling the air brake equipment is left to the discretion of the individual railroad. However, when braking with power, it must be remembered that for any given throttle position, the draw bar pull rapidly increases as the train speed decreases. This pull might become great enough to part the train unless the throttle is reduced as the train speed decreases. Since the pull of the locomotive is indicated by the amperage on the load meter, the operator can maintain a constant pull on the train during a slow down by keeping a steady amperage on the load meter. This is accomplished by reducing the throttle a notch whenever the amperage starts to increase. It is recommended that the independent brakes be kept fully released during power braking. The throttle must be in IDLE before the locomotive comes to a stop.


You don’t ever want to be standing still with power applied. This can result in stall burns to the traction motor commutators and raised bars which will result in a flashover later on. The practice of some engineers on commuter railroads of remaining in throttle one to cancel blended braking while stopping and standing, causes unnecessary strain on the traction motors. Here is some applicable operators manual text:

POWER AT STALL
Do not hold the train at standstill on a grade or with the brakes applied and the throttle open for power. Extensive damage to the traction motors is possible.

I hope this helps.

PC

Wow-thank you, Preston!
Just one thing I'd like to clarify-if I am power braking by alternating between throttle notch one and notch 2, and drawing 400-600 amps for no more than 2 minutes-is that bad?
Note that the throttle is shut off the instant I come to a halt.

I understand that someone with more experience can stop smoothly, right on the mark, without power braking and associated amps-but I am not there yet.

John, if I am paying for the fuel you use and the brake shoes and wheels, yes that is bad, but as you become more accustumed to the locomotive and the terrain you operate on, your train handling ability shoud improve and you will find you will be able to stop the train more precisly with less and less power braking. Experience and asking questions are both good teachers and Preston is one of the best at answering questions.
Good luck honing your skills,
Mike Tillger

Great discussion, but one thought... Any surviving GP-30 is unlikely to still have D-57 traction motors... The UP locomotive at Nevada State Railroad Museum in Boulder City has D-77 motors... as each was replaced it was upgraded with the then current traction motor... our NW-2 which was built with D-27 traction motors also had D-77 traction motors.

EMD Engineering did a study of the GP30 with traction motor upgrades and made a recommendation that the ratings should not be increased going from D57 to D67 or D77 motors. I take this as an indication that the D22 main generator was being pushed as hard as they wanted with the original ratings. Keep in mind that going from 980 amps to 1050 amps on four motors connected in parallel is 280 amperes additional current required from the main generator. The question of whether a traction motor upgrade will provide a benefit in continuous or short time ratings depends upon both the type of motors and the type of main generator.

On an NW-2 upgraded to D77 motors, the Engineering Department recommended 800 amps continuous rating.

An NW-2 cost $84,300 in 1939.

PC

My (admittedly uninformed by experience) is that the expressed concern over "400 amps" has little if anything to do with overloading the traction motors, but indicates there is 'too much motoring' going on at that point in the deceleration.

If we look at the instruction Mr. Cook provided, there are two disparate things going on. One is that during the early part of the deceleration, a fixed amp draw is being maintained as way comes increasingly off the train. But the other is that the throttle "should" be at idle before the train actually stops. Now, in my opinion the purpose of stretch braking is a smoother stop for the passengers and a smoother start afterwards, rather than dragging the train to a predetermined spot (which would be done at comparatively low speed while 'learning' and would be governed by acceptable short-term rating). What I see implied is that, after a certain point in the deceleration, the amps should be gradually decreased below the 'constant amperage' as you get closer to the actual stop, with the throttle at idle as the train actually is allowed to stop with the applied brakes.

As I understand it, the concern about '400 amps' would be that he was using too much power at that slower speed, not that there was danger of damage to the locomotive or the shoes and wheels on the cars from too much current in the motors at that time.

The WLE did some plug loading at several mines not long after they took over. Those were two SD-45s with a slug in between, plus one GP-35 typically. I've seen cast EMC motor casings up until I retired going on 6 years ago. The main difference is armature cooling. Everything has to fit in the same package. And do more with the available air supply that varies by engine RPM. There may be things they did to keep the coils cooler. In my experience the GE 752 was a much more rugged motor. and they were on the majority of the WLE's GP-35's.

Couple more differences, pre GP-30 with its centralized air system which became the EMD standard, individual traction motor blowers were driven from the companion alternator at a nominal 215v three phase. So the faster the alternator turned the faster the blowers turned. And in many applications weren't even fused. EMD's are very forgiving. We pulled in a GP-35 and discovered that there were three different styles of power assembly's in the prime mover. 567 and 645 and the loco didn't seem to mind at all.