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CraziestOzzy

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Joined: 11/07/2008
Location: Australia
Posts: 135

Posted: 01:20am 28 Feb 2009

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I managed to grab a newer version of the F&P smartdrive motor. 60 series I believe.
The motor itself is electrically fine.
The motor winding is typical three phase wye (star) with a central neutral point.
Without changing any wiring to the rotor, I wired the unit to output DC...

I use six IN5408 schottky diodes rated at 3amps to form the rectifier. I will beef up the diodes later but the ones I am using are suitable for hand turning and impressing the missus.
My problem is simple and it is often the simple problems that cause me heartache. Not sure if it is even a problem

No matter what configuration I use with T1, T2 and T3 (such as using phase to neutral or phase to phase or even the one I show above) I still short the motor out when attached to a load such as a light bulb or smaller DC motor. So turning the motor by hand is near impossible.
Without load, the motor puts out some impressive voltages (+100 DC) at low RPM'S turned by hand. T1,2 & 3 have equivalent voltage output. Also, all three output leads have similar resistance values, so no problem there I believe.
I need to know what I need to do to stop this "braking" effect when motor is under load so I can turn the motor by hand to light a simple light bulb. Should I be chucking in another electronic bit to make this work without requiring muscle to turn it?
I have read nearly all posts here and searched Google, but can't seem to find an answer to what I know is staring me in the face

PS...That stator work I posted a while back is still on the go. All laminates are polished and coated ready to press together...been to busy of late.

http://cr4.globalspec.com/member?u=25757

http://www.instructables.com/member/OzzyRoo/

Gizmo

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Joined: 05/06/2004
Location: Australia
Posts: 5119

Posted: 03:21am 28 Feb 2009

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What you are expierencing is reality, the laws of physics.

With no load, the alternator is easy to turn. With a load, it becomes harder to turn. There is nothing wrong with your circuit. Connect up a 25watt light bulb and you will feel the loading as your mechanical energy is converted into electrical energy, and then into light and heat at the light bulb. Connect up a 100watt bulb and it will be very hard to turn by hand. Convert it to pedal power, and using your more powerfull leg muscles, you can get over 300 watts for short periods.

It makes you appreciate how much energy is needed to power something as simple as a lightbulb. It would take a team of 5 people to pedal power a toaster!

Note, spinning the F&P, even by hand, can make enough voltage to kill someone, be very careful please.

Glenn

The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ

CraziestOzzy

Senior Member

Joined: 11/07/2008
Location: Australia
Posts: 135

Posted: 03:36am 28 Feb 2009

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Gizmo said Note, spinning the F&P, even by hand, can make enough voltage to kill someone, be very careful please.

Very true and thanks for bringing that point up for others.

As to the "problem" I have...ain't physics grand

Thanks for putting me back on the straight and narrow, I thought I was loosing it - bugger, I already have

http://cr4.globalspec.com/member?u=25757

http://www.instructables.com/member/OzzyRoo/

KiwiJohn
Guru

Joined: 01/12/2005
Location: New Zealand
Posts: 691

Posted: 03:47am 28 Feb 2009

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The light bulb plays tricks on you when you try this sort of thing! The cold resistance of the light bulb is very low so although it may be a 25watt bulb it behaves when cold like a much bigger bulb!

If you summon all your strength and try really hard to turn the F&P it should suddenly get easier once the bulb lights. (I think

)

CraziestOzzy

Senior Member

Joined: 11/07/2008
Location: Australia
Posts: 135

Posted: 04:05am 28 Feb 2009

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So true KiwiJohn.
Think I might try some more muscle to get that globe doing something useful, as I need to make the missus think I am doing something worthwhile

Might play with some bad-ass capacitors rigged up to a few non-linear IC's fed from a 9 volt battery and see if I can sorta make things easier (don't try this at home) and not go ***BANG*** while I feed off the remaining juice in the caps to light my bulb

http://cr4.globalspec.com/member?u=25757

http://www.instructables.com/member/OzzyRoo/

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