[katkinkate]

I read somewhere recently about electrical motors, like ones that drive a fan or washing machine can become generators if you can make them turn the other way. Is this right? If it is, how come people don't just use them for wind generation instead of fiddling around with magnets? I freely admit little electrical knowledge and apologise if this question is 'stupid'.

I do remember my dad giving me an electrical shock from an old alternator he was fiddling around with, when I was a kid. Maybe we could connect wind turbines to old alternators to make electricity. I suspect the reason why these aren't being used is that the person who wrote what I described above was wrong, or the yield is just too small to bother with. Can someone clear this up for me? Ta muchly.

[argyle]

About the alternator, this can be done, but you prob. need to "redo the coils" of the alternator, or it will need a way to high rotation of the spinning of the magnets.

I believe an laternator also need some power to activate the magnets..

[Newfie]

Alternators on cars use the cars engine rotation to make electricity to recharge the battery.

So yes you CAN do it.

All the fun is in the how.

If you are interested in this sort of thing I would suggest you research on marine wind generators. Lots of guys out there trying to live the dream on the cheap.

A lot of the issue is not so much how to produce the power but how to maintain your batteries so you don't over cook them.

I even read a post on how to WELD with your alternator.

[patience]

Alternators, when new, require an applied current (from the car battery) to the field coils to start generating. Old used ones often retain enough magnetism to self-excite without the battery current to the field.

katkinkate,

There are ways to make motors act as generators, but the matter is one of appropriateness for a specific use. All motors are not created equal, there being many kinds. Wind generation is unique, in that the rotors turn rather slowly compared to motors and alternators/generators. So, either you use some kind of gear drive to speed up the generator, or you make an alternator or generator that can work at low speeds, which means one of comparatively large diameter. My son in law has done that, and I build the metal parts for it. It is 16" in diameter for a 10 foot diameter windmill. It is designed to work at 200 RPM. Car alternators are about half that size and want to run at around 2,000 to 5,000 RPM.

Permanent magnet motors, such as those used in treadmill exercise machines, can generate at rather low RPMs, but are small output and are not waterproof--a big problem for outdoors. Nor do they have adequate bearings for supporting a windmill rotor to run attached to their shafts. It can be done, but is not durable. A 90 volt permanent magnet waterproof motor can generate 12 to 15 volts at 200 to 300 RPMs, but new cost is as much as a suitable alternator that is better for the job. We have done that with a salvaged (free) DC motor, but for the real thing, you get to make a special alternator, or run a gear or chain drive to speed up a car alternator.

These are just our anecdotal experiences. This is a very deep subject, that could take days to elaborate in detail.

[patience]

More info on building your own windmills, including a discussion forum, are at this site.

http://www.otherpower.com/

Sharp folks there, who are actually doing this.

[small_steps]

More and more often, motors are being manufactured with permanent magnets (PM). So with these PM machines, all you need to do is rotate the rotor to obtain voltage at the terminals. The rotation results in changing flux linkage, so you have voltage per Faraday's law. In other machines, specifically induction machines, you need to establish flux in the machine as well as the rotation, so you need to apply a capacitor to supply reactive current, or have a power converter to do the same. For cheaper (and older) machines which are typically found in fans etc, you are pretty much SOL. Except for the larger machines (i.e. MW class), if you need to magnetize the machine, that is create the flux in the machine (via field winding), forget it, its not worth the effort.

Perhaps this helped...

[WisJim]

Maybe Kate is thinking of induction motors which work as induction generators if they are turned faster than the speed that they run as a motor. This is the kind of generator used in most larger wind generators since they don't require an inverter to change their output to match the grid, only some much simpler controls.

[katkinkate]

Thanks folks. Sorry it took so long to get back to you. All very interesting, but sounds like I need to understand a bit more about electricity in general before trying it myself. I read about it for the first time in a blog and wasn't sure if the guy knew what he was doing. Thanks for your help.