I have a contact who is looking to repower a diesel electric tugboat. The original generator is gone and the drive motor is missing its armature. However, the motor looked similar to a locomotive generator and that got me thinking. Could this tugboat be outfitted with a couple of locomotive generators with one acting as the drive motor? My contact says he can get a pair of EMD D4D traction generators for a good deal. Would such an arrangement work from the electrical aspect?

The original DC drive motor was rated for 1020 horsepower at 700 volts and 700/875 RPM. The system appeared to have a Ward Leonard style control. The controls would also need to be rebuilt from scratch. Apparently the tug sank at one time and destroyed the electrical system onboard.

If your talking about the literal diesel locomotive generator, sure.

recall what regenerative braking is, the motors on the trucks are turned into generators producing electicity, that also produces a magnetic braking effect, done very common on electric railroads used on heavy grades, the train going down on regenerative braking would help powerize a train going uphill. Unfortunate for diesels this power is heated off by resistor banks with no regenerative use of the power, but it saves the use of the brakes when you don't need to apply them as each application is wear and tear on brakes, however much or little wear that is.

The newer AC traction motors might make a nice alternator when coupled with a big diesel engine about the size of an "18 wheeler" engine, if the output was stable 3-phase 60hz like we run everything in the USA on.

When initiating dynamic braking on the less than 20 years old diesels, doesn't the locomotives engine rev up to a high throttle number, like notch 7 or 8 to keep things powered up to a certain volt/amps? Would that be to keep the exciter current constant to the traction motors receiving a stabile current?

That might also mean that the motors give off a stabile and desirable current (like maybe 3-phase 60hz) current at that same RPM that is equal to the notch 7 or 8 RPM, maybe 900-1000 rpm). Hum...

So if you drove the traction motors up to 1000rpm witha gear box and some kind of big motor, you might get usable (for anything 3-phase) high volts and amp current at 60hz.

I'm not up on EMD nomenclature but all EMD locomotive generators since the GP30 actually produce AC current which is rectified to DC. You could not convert one to a motor and power it from a DC source.

just thinking, we have AC motors, AC generator and frequency timing gets you speed control.

Might be a little more than the repairing job needs to be...thats a lot of custom work and huge power components to do it.

Many years ago I sold deep well pumps for municipal watering. We had one that would pump when powered and when the upper resevoir was filled, would run as a generator by driving the falling water through the impellor. There was enough electricity generated to run the entire pumping station and feed into the grid. Neat, huh?

Later!
Mr. Ed

The D4Ds were used on the E8s. They are pure DC generators. And from Electric Motors 101 we learn that a DC motor and a DC generator are identical machines, so conceivably this setup should work. These generators are probably the best solution to this problem since:

1) they closely resemble to original equipment in size and appearance (important on a preserved vessel)
2) the RPM of the ship's diesel engine is very close to the RPM of an EMD 567 at full load.
3) the desired shaft RPMs match what the generator acting as a motor would put out at full load.

What I don't know is how the D4Ds are wound. Are they shunt wound or compound? Also not sure if there are any other unforseen features of these generators that I might not know of. I come here to do a little fishing for info. hoping that an EMD electrical expert might chime in.

As for heavy complex control equipment, I could lay my hands on as many big DC contactors that I wanted to carry out of some of the mills that I work in, and as many big rheostats as I want as well. What would make this a fun project for me is if the boat was docked up on Lake Erie instead of on the coast of California.

I'm pretty sure that all turbocharged EMD's up through the GP35 used d.c. generators; EMD introduced alternators on the 3000- and 3600-hp 40 and 45 series. All normally aspirated EMDs through the early GP38s used d.c. generators; the GP38AC was designated as such because it had an alternator rather than a generator. Not sure what the story was on the switchers, but it's possible that everything up through the SW1500/MP15 had generators. Preston?

Walt Lankenau

Walt- Now that you point out the GP38AC, I remember you're right. It's been almost 30 years since I studied the subject; my brain's getting a bit rusty. I don't know why I was thinking the GP-30's had AC generators; I do remember they had about umpteen steps of transition.

I do keep my steam locomotive specs straight though... :-)

Maybe 20 years ago I had an interesting discussion with a gent that had an EMD SW-1, purchased from a power plant, that had been redone with a Cat or Cummins "truck" engine. He described the traction generator as being another traction motor, similar to the ones still on the axles. He said the unit was very easy on fuel, and worked just fine.

The GP-35 was the last gasp, horsepower wise, for EMD's use of a DC generator. To effectively use any more horsepower, the DC generator would have had to be larger that the confines of the typical road-switcher hood. As it was, the GP-30, GP-35 and the Alco C-424 and C-628 had to use many stages of field shunting to match engine HP to generator to TMs. True, the U-25 and C-425 had somewhat larger generators. but they were only 2500 HP, and avoided the multi-stage field shunting issues. All three builders used alternators and rectifiers for their 3000 HP and up offerings.

The GP-38AC option was born of a need to reduce generator maintenance. Brushes wear out a lot faster than diodes and rectifiers. Even the smaller units of today, the genset switchers, with multiple 700 HP engines, use alternators. The alternator is just that much more simple to maintain, even in that smaller size.

edit: I believe the MP-15 was offered in both AC and DC versions. (And wasn't that the one that had either a normally aspirated 16 cyl. or a turboed 12 cyl. engine?)

Yes thats correct I know the MP-15T somewhat.

I should have looked it up!

Actually, it was either a roots blown 12 cylinder (in the MP15DC and MP15AC), or a turbocharged 8 cylinder (in the MP15T) ...there is no such thing as a "naturally aspirated" EMD 567, 645, or 710.

Jeff

I should have looked it up (MP15T)! I remembered the Turbo on the smaller engine, but the facts got scrambled

Just about 10 years ago I could buy any part of a locomotive, including traction motors, etc.. at the local rail scrap yard south of Dallas, its about 20 minutes down the road in Rio Vista, but they never get any locomotives any more. I'm told the locos all go to a large "Progress Rail" scrap yard close to Houston now.

Does anyone here live close to that location?

EMD built the D32 both as a generator and as a motor. The D32 motor was used in some marine installations and also was widely used in oil drilling applications.

I am unaware of any motor adaptations of the D4D, if they did them, I have never seen one.

A D4D has shunt, differential, battery and starting fields as well as interpoles.

PC