120 volt, 15,000 watt dc generator conversion

[kato]

Anyone out there have any ideas or uses for a surplus 15,000 watt, 120 volt dc, propane, natural gas generator.
It was a former computer room standbye battery ups power supply and charger. Very few hours on this baby.
Any one have any ideas what I can do with this, I got a deal on it, thinking I could convert it to 48 volts dc for solar system battery charging, or to 120 volt ac but its a processer controlled system, how expensive would it be to drop the voltage to 48 volts and still get the 100 or so amps for battery charging. Is there a device I could build economically to do this?
Any hints or maybe just point me in the right direction would be appreciated.

[russlk]

How is the DC produced? Is it a motor-generator (rotating machinery)?

[toejam]

wow that's a neat find.You should be able to get that thing to produce most any voltage you want to by varying the amount of power applied to the field winding.You will have to find the connections to the field and check the volts there.I suspect it to be the same as the output.To lower the output less field voltage (average field voltage).The way the computer does this compares to a coil that pulls an armature in that opens set of points that connects the field in series with the armature.I did the very same thing on an old budda alternator.The voltage was controled by adjusting a screw that determined at what tension the points opened.good luck!
tj

[Chris Smith]

10 X 12 volt batteries is 120 volts. Perhaps 9 would be better at 13.3 volts, or 8 at 15 volts. [a little high] <p> 13.6 to 14.2 volts is the standard range for lead acid car batteries and you can tap off four batteries to achieve the 48 volts for your other apps. You would two sets of four batteries to tap off of, plus one spare to tap 12 volts off for other apps.

[kato]

The engine is a mitsubishi 4 cylinder car engine turning a humungous alternator.
which then feeds a processor controlled voltage control package.
the thing weighs in at over a thousand pounds.
I suspect it is a dc alternator, but if it was an ac alternator, I could convert the voltage with a large industrial step down transfomer.
Im going to check out the winding scenario first, the 120 volt battery bank idea sounds good, but Im afraid if I conect the feeds of 48 volts wrong and get a back feed of high voltage, the 3,000 dollar invertor will go poof , with a cute little mushroom cloud.
I would have to use big diodes to protect it, those sound very expensive.

[toejam]

crank that thing up and put a meter on it.You don't have to use all the current it can produce and 200 a 100 volt diode packs are not that expensive,If nothing else you can use it to make hot water while doing your wash.

[Chris Smith]

If you hook up the 48 volts wrong, you will need new wires, not a new generator. The batteries will protect you for the most part giving a instant wire melting 1000 plus amps or more. Not good for the batteries but they are tough for the most part.

[toejam]

I would most certianly insert a fuse in series with the output.Thrs probably a 150 or so amp fuse there somewhere i'd get a 10 amp fuse and maybe a old dryer element for load testing.One thing you may find is a warm up circut that limits the engines rpm till it warms up.If that's so, you may not get any output till it reaches operating temp.
tj

[russlk]

If it is a DC generator, it will have a commutator and two brushes. If it is an AC alternator rectified to DC, it will have six large diodes somewhere.

[Lee McVey]

Perry: Since it has a microprocessor-based regulator, my best guess is that it is a DC generator. Voltage control with an AC machine is not easily accomplished over a significant range.<p>If you can examine the voltage regulator and find its voltage sensing input which is probably some form of voltage divider, you might be able to 'fool' it by changing values so that it will reduce the field excitation and corresponding output voltage. If you can find it, you could measure its input resistance and build your own divider at a low enough equivalent resistance externally so you accomplish the same thing.<p>A DC machine has really a wide output voltage range, so if that's what you have, you should be able to jerry rig it down to 48VDC by fooling the regulator.<p>Good luck.<p>Lee<p>60HzEE