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 http://bbs.homeshopmachinist.net//smile.gif

[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.

[J. Randall]

Weird, I wired one of those up on a meter proving truck back in the 70's. As I remember it worked allright. I don't remember the details, but I had to cut into the wiring inside the alternator. I put an anti-dieseling solonoid on the carb, just flipped a toggle switch and it kicked up to the correct rpm to run an electric drill and impact wrench. James

[spkrman15]

So it is possible. Ok but now how feasible is it? From some of the web pages i read it mentioned a 3.5 hp to get 900 watts. Seems like alot of work for little results.

What do you all think?

Where is a good spot to track down those capacitators and how do you check to see if they are good?

Rob http://bbs.homeshopmachinist.net//smile.gif

[PTSideshow]

Ok here is a magazine for all your home powere needs.
http://www.homepower.com/
and http://i35.photobucket.com/albums/d200/ptsideshow/generator.jpg
This may be of interst to check out the instruction booklets on line use the item number to see if they have them stored on line.

------------------
Glen
Been there, probally broke it doing that

[J Tiers]

<font face="Verdana, Arial" size="2">Originally posted by spkrman15:
So it is possible. Ok but now how feasible is it? From some of the web pages i read it mentioned a 3.5 hp to get 900 watts. Seems like alot of work for little results.

</font>

I don't think its 3.5 HP INPUT. You may have to oversize the motor, because the magnetizing currents through the capacitors also cause heating added to the load currents. There may be a thermal issue.

Also belt drive can sop up immense amounts of power, depending.

You might have to have an engine 2X power or more, if its a modern "little screamer" that has to go 2500 rpm to put out. They may need to be oversized at least 2 to 1 versus the load.

An old low rpm farm engine would not be a problem power wise rated at the output plus losses alone.

[spkrman15]

I went to the web page Evan metioned above. Would these capacitors work?

http://cgi.ebay.ca/045L-Nippon-200v-1000uF-Electrolytic-Capacitors-Qty-25_W0QQitemZ7577296852QQcategoryZ116999QQrdZ1QQcmd ZViewItem#ebayphotohosting

Is there a difference from VAC and VDC ? From what i know it is Voltage Alternating current (VAC) and VDC is Voltage Direct Current.

Rob http://bbs.homeshopmachinist.net//smile.gif

[Evan]

Those will not work. They are DC electrolytic capacitors. You need standard AC motor run capacitors. Start caps won't do either as they aren't rated for continuous duty.

[darryl]

Buddy of mine had the alternator conversion package installed in his van. It certainly ran the skilsaw without any trouble. There was an expensive option to control the throttle, but he just cranked up the throttle from under the hood and used a vice grip to keep it there. He and his dad built their shop using it, but he was choked he couldn't use the table saw off it. Ac/dc motors only, but no limitation on lighting.

As I understood it, there was no change in the internal wiring of the alternator, so the original diodes were used. My thought was, and still is, for the safety of those diodes with that high a voltage capability being required from them. I've also wondered about the temperature rise in the field winding (the rotor). If there had been any problem with this alternator conversion, I would have heard about it, but I never did. This guy also ran one of those tire-powered welders- you know, jack up a rear wheel and set it down on the rollers, block the other wheel, and go for it. That worked to his satisfaction as well, though it sure looked like an accident waiting to happen.

[Evan]

I have a 2000 watt Generac under the hood of my Ford Ranger. It goes where the air conditioning would be since we don't need much of that. I slip on the belt when needed and set the idle to 1200. Together with the pulley ratios that gives ~60 cycle at 120 volts.