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Military MEP and Aircraft Gen-Sets MEP Mobile Electric Power, APU Auxiliary Power Unit and other military surplus generators.

Military MEP and Aircraft Gen-Sets

GE 45KW Generator


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  #1  
Old 04-30-2016, 02:23:34 AM
dwight44 dwight44 is offline
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Default GE 45KW Generator

I have a Mil GenSet from 1969 with a GE 45KW generator run by a GM 3-71 diesel engine. I have been all over the web trying to find service info on the generator and can not find anything. Does anyone know where I might locate a schematic or any service info on this or a similar generator?

This one is a GE 5SJ4326P23Y41 but anything similar should give me the info I need. There was a guy named Tunnelport who has the same unit and was looking for info on it back in 2009 but apparently he eventually gave up trying to get it running.

It has a couple 500V SCRs (in parallel) and a large diode in series with the SCRs that supply the field current so it SHOULD be getting a nice smooth DC current but the generator seems to put out about half the voltage it is supposed to so SOMETHING is wrong.

Any help would be very much appreciated!
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  #2  
Old 04-30-2016, 09:51:13 AM
Birken Vogt Birken Vogt is offline
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Default Re: GE 45KW generator

Can the whole enchilada be ripped out and replaced with a modern regulator setup? What is this SCR thing sending power to? I assume stationary field windings, or possibly some brushes?
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Old 05-01-2016, 01:10:01 AM
dwight44 dwight44 is offline
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Default Re: GE 45KW generator

The unit has two regulated functions, the frequency which is controlled by the RPM of the engine (1800 RPM) and the voltage which is controlled by the voltage provided to the rotor in the generator. The more voltage, the stronger the rotor magnetism thus the more voltage the generator supplies. Both are controlled within + or - 1% f it is working OK which is quite good. Both of these are also manually adjustable from the control console and you can adjust the voltage to the rotor from about 6 volts to about 75 volts. The trouble seems to be that it doesn't provide any power until the control votag3e reaches about 30 volts and then it shoots up to full voltage and stays there until you reduce the control voltage to about 20 volts where it just turns off and doesn't supply any power to the rotor.

The thing is that I already have a perfectly good 25KW generator that runs my house and this is just a project to see if I can get the nearly 50 year old generator working again. Rumor has it that it last ran about 15 to twenty years ago but there is no one alive that knows if it EVER actually produced usable power. The Unit was built by Sun Electric Company of Crystal Lake IL and apparently they built very few of them and service information seems to be non-existent. I have pulled all the circuit boards and found numerous bad solder joints and bad transistors which makes me suspicious that it never actually worked as designed. The trick is that it has a lot of circuitry that allows it to be connected in sync with other generators and even the utility grid and some of the bad devices MIGHT belong to these functions which I would never have any need for.

There have been others looking for information for these units over the years, most recently gtochuck back in 2013 but no one seems to have had any success.
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Old 05-01-2016, 10:11:13 AM
Birken Vogt Birken Vogt is offline
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Default Re: GE 45KW generator

The control voltage you mention is DC going to the field windings of the generator, correct? And output voltage is not rising and falling in lock step with field voltage?
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Old 05-01-2016, 02:46:34 PM
dwight44 dwight44 is offline
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Default Re: GE 45KW generator

The control voltage TO the SCRs goes up and down OK. Trouble is that the SCRs don't seem to turn on until the voltage reaches about 30 volts and then they turn on FULL. They stay on full until the control voltage goes down to about 20 volts and then it turns completely off. They SHOULD be turning on and off gradually in concert with the control voltage.

Another problem is that when the field voltage DOES come on, the output voltage of the generator only goes up to about half of what it should. I would suspect that these problems are somehow connected but I don't see why or how. One would think that when the field voltage shoots up to 75 volts (full on) that the generator voltage would also shoot up the way OVER the normal output. There have got to be schematics of these GE generators SOMEWHERE but GE apparently does not have them posted and no one else seems to either.

The circuit boards are poorly designed which probably accounts for their unreliable behavior. They have leads on BOTH sides of the boards and some of the leads on the component sides of the boards did not get soldered. They probably worked long enough to pass a Quality Control test through a physical contact but then failed as soon as any corrosion started. They probably had many failures which might account for their scarcity and lack of service information.

They have something called a "sequencer" board that apparently shoots 24 volts the the field windings when the generator is first started and then the control circuits switch to 120 volts AC which SHOULD have been generated by the generator itself by that time. Since there is no 120 volts being generated, all the control circuits drop out a few seconds of operation and the whole thing shuts down. The way I got the control circuits operating long enough to collect some voltages was to isolate the generator from the control circuits and run them from line current. I also had to supply the actual engine governor (a Woodward 2301) with 24 volts directly from the batteries. This also s run through the "sequencer" circuit as well as other boards. They supply 24 volts to the Woodward 2301 boards long enough for the engine to start and then go into "run" mode where the boards shortly turn off the power to the Woodward governor and the engine shuts down. After I replaced some transistors and soldered some bad joints, I got this circuit to run but then the safety circuit senses a low voltage situation and puts the whole system in "emergency stop"! It has a switch that bypasses the safety sensors but when THAT is thrown, you can not START the unit! I have the start it and immediately switch the bypass switch and then it will run fine but it STILL is not producing usable current.

As you can surmise, the unit is quite complicated and especially without any former experience with these units and no service info. Just winging it and learning as I go along!
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Old 05-01-2016, 09:27:52 PM
Birken Vogt Birken Vogt is offline
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Default Re: GE 45KW generator

Does the nameplate have field voltage/current stated?

I am speculating here but I wonder if a rotating diode out might cause the field voltage requirement to be higher than normal. Such that 75 volts does not drive it full.

On the other hand, it could be that it takes more than 75 volts normally. If the rotating diodes check OK then my next step if it were mine would be to drive it with higher DC voltage from an external source until it works.

Gauge of winding in the stationary field winding and ohms would help to know whether it expects higher voltage or is going to fry from overdriving it.

In any case, if it were mine my plan would be to replace the regulation setup with something modern, and possibly the engine controls also.
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Old 05-01-2016, 10:41:07 PM
Wayne 440 Wayne 440 is offline
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Default Re: GE 45KW generator

Quote:
Originally Posted by Birken Vogt View Post
...if it were mine my plan would be to replace the regulation setup with something modern, and possibly the engine controls also.
+1 for the above advice. Some relative of Rube Goldberg must have worked for Sun back then.
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Old 05-01-2016, 11:03:07 PM
moteurdelco moteurdelco is offline
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Default Re: GE 45KW generator

Is it brushless? or is exciting to main rotor slip rings?
old generator were often designed to operate with 125vdc ;supplied with belt driven exciter,upgraded(modernize) with ''static exciter'' (controlled scr bridge),like Onan's and Caterpillar. did you mesure 60 hz?? what kind of governor on the 3-71? GM generator engines were habitually equiped with hydraulic governor.
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Old 05-02-2016, 11:46:02 PM
dwight44 dwight44 is offline
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Default Re: GE 45KW generator

The trick is that this is an exercise to see if I can get the generator running AS IS! I have a (25KW) generator to run my house so I don't want or need to put thousands of dollars into this machine just to produce power. The challenge is to get THIS machine running as it did when new. I have numerous "hit & miss" engines and steam engines that I have restored, not to actually drive something, but to just see them run!!!

This machine is a lot more complicated than anything I have tackled so far but in that it uses discrete components without a bunch of IC chips I think I have a chance. It is just a great challenge trying to get it running without ANY servicing information as to what and how all the circuit boards do. I am trying to figure out the whole system without having prior knowledge of any similar machine so...

This thing weighs 3600 lbs so removing the engine/generator package and then separating the engine and generator is not something I want to tackle without some reason to think that something is wrong with the generator. If I had a schematic for the generator, I could do some tests and see if there was an internal problem and I don't see why there would be any diodes or ANY solid state devices internal to the generator as it is SUPPOSED to provide AC current.

The rotor should only need DC current to make AC in the stator so...

Another thought, I have never fooled with a 2 cycle diesel engine and it is possible that I am trying to run it much slower than what is called for. I realize that it has two power cycles in place of what I am used to with the numerous "four cycle" diesels I am used to but I don't have any way to tell how fast the engine is running except by the sound. Does anyone have access to a "U-Tube of a 3-71 running at something near 1800 RPM that I could listen to? I am afraid of running this engine too fast and harming it but there is no way to tell how fast it is going except the voltage and frequency gauges. Do these things really sound like they are blowing up when they run? I just have no experience with two cycle diesel engines.

You guys are asking question that I can not answer without a schematic OR just physically tearing the whole machine apart which would be a major effort and might not be necessary.

The unit only has a little over 100 hours running in its lifetime so I doubt there is anything physically wrong with the generator itself and I feel the problem probably is with the control circuits and they are a whole lot smaller and easier to deal with than tearing apart the engine/generator package.

It just seems like SOMEWHERE on the WWW there has to be a schematic for this generator, the trick is how to find it.

Any suggestions?

Thanks,
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  #10  
Old 05-03-2016, 12:07:28 AM
Birken Vogt Birken Vogt is offline
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Default Re: GE 45KW generator

To set engine speed, get a good Fluke voltmeter with a Hz function and measure the output leads and set to 60 Hz. Even with no real output the meter will still pick it up OK.

I used to take care of a similar vintage but a lot smaller and it had next to nothing for manuals. I had a schematic but I don't know where it has got to now.

Those military machines were hyper complicated and used a lot of crazy specialized components like multi tapped transformers and saturable core magnetics to do simple things so they are very hard to figure let alone actually repair.

I would guess yours is one of less than 10 in existence if I had to guess on these. Most have been to the scrap yard by now.
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