auxilary power

[spkrman15]

Can you use any 3 pahse motor to make power? If i was to take a gas engine and power a 3 phase 15hp induction motor, turn it at 1750 rpms (the motor's operating range) would i get 12 to 15 amps of 3 phase power?

Rob

[Forrest Addy]

Nope. Three phase induction motors do not self-generate. They have to have some form of excitation so the rotor turns into a magnet that sweeps the stator windings to induce EMF. Besides you need to run the motor a bit faster than synch RPM (1800 in your example to get full voltage thanks to the motor's internal losses.

AC generators are called "alternators" and have a wound armature that's supplied with DC (excitation) to make it a rotating magnet. Most also have voltage regulation that adjusts the excitation to keep the output voltage constant regardless of load.

[J Tiers]

Uh, oh.....

Gonna have to disagree with Forrest sort of.....

I have done the generator trick..... you need some residual magnetism in the stator to start it, and some suitable value capacitors to maintain exitation.

The residual field creates some rotor current. That then generates some stator voltage. With a load such as the excitation caps, it starts getting output current, which then creates a field, and produces more rotor current. it "builds up" somewhat like a shunt DC generator.

And, if overloaded, it also "collapses" like a shunt DC generator (load reduces "field voltage", rotor current is reduced, voltage decreases, etc, etc).

But it works. It's a cheap generator for remote locations.

Yes there is some issue with voltage, you can get proper voltage OR proper frequency, but usually not both, right out of the motor. If you adjust the load and the exitation caps you may be able to get an optimum.

[Evan]

Look here:

http://www.qsl.net/ns8o/Induction_Generator.html

[darryl]

Hmm I wouldn't have thunk it possible.

[Dawai]

I have heard of car altenators being rewound to provide 3 phase, saw generators on boom trucks that were.

During the blizzard of 93, I wired a saw into the altenator on my 64 El Camino to run. About 4,000rpm it produced 80 volts..saw did not heat up.. brush motor..

[wierdscience]

<font face="Verdana, Arial" size="2">Originally posted by David E Cofer:
I have heard of car altenators being rewound to provide 3 phase, saw generators on boom trucks that were.

During the blizzard of 93, I wired a saw into the altenator on my 64 El Camino to run. About 4,000rpm it produced 80 volts..saw did not heat up.. brush motor..</font>

Yep,car altenators are three phase,that's the reason for the triode bank.

My buddy down the road had the little altenator book from linsay that claimed you could get 4,000 watts from a 105 amp altenator.Seems like you had to remove the diode bank and voltage reg ,build a new reg and spin it up to 7200 rpm to get 110vac out of one.I was skeptical,until I saw this -

http://mywebpages.comcast.net/t.molnar/Obwelder1.htm

I intended to add one to my winch truck,but haven't gotten around to it yet,maybe I will before too long.

[wierdscience]

On a seperate note,I have wondered if a 3~ motor could be taken apart and the rotor be drilled and milled so it could be wound for coils with a hole gundrilled through the rear half of the motor shaft allowing the coil ends to be brought out to the back endbell and connected to slip rings.If you excited it while spinning the shaft at 1800 rpm(1800 nominal nameplate rpm on the donor)would it produce 3~ power?I'm think it would,dunno how efficient it would be thou.

[Dawai]

That was a pre-internal regulator chevy I ran the saw with.. if you want to copy.. I required no parts, tied the fields up hot, and it throwed out full juice.

I ran the van next to it charging the battery with booster cables.

Doc (my buddy) his eyes get misty as he recalls I managed to cut up firewood to keep the family warm. He brags on me so much I sometimes wonder who he is talking about. I don't remember half the crap he tells personally. (yeah I used to drink a lot)

Ohh, and it was 23" snow that shut down georgia in 93.. not much for you northern people. Roofs fell in everywhere.

Weird, just insert magnets?? it should generate something.. To check a harley altenator there at the plug? you wire in a 120 volt light bulb in a rubber socket.. if it be charging, the light be shinin..

[This message has been edited by David E Cofer (edited 01-04-2006).]

[wierdscience]

Magnets huh?That might be a neat experiment,I got a some Neo mags here somewhere.

Ever see one of those kits that were made for use in a small van or RV that were made before inverters came along?It wired into the altenator and had two 110 outlets in the van and a switch in the dash,you left the motor running and flipped a switch to get 110,plus it also had a built in 12vdc supply to run the ignition.Dunno if the worked good or not.