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davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499
Posted: 11:40pm 22 Jul 2014
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I am using one of the older Gentle Annie PM motors as a generator in my microhydro installation. I was getting about 125Watts out of it until a few weeks ago it dropped to about 100Watts.
Running the motor unloaded I get 63VAC across two of the phases. The third phase however measures 51VAC. Ignoring things like frequency, all phases use to be the same.
I would have thought a shorted turn or open winding would result in zero Volts out of the one winding and possibly an affect on the others.
Appreciate any comments from 3 phase or multi-phase generator experts.
Thanks,
Dave
BobD Guru Joined: 07/12/2011 Location: AustraliaPosts: 935
Posted: 12:00am 23 Jul 2014
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Me no expert but if you can get access to both ends of each phase winding then I would do an ohms check and see if any difference between the windings. Also check both ends of each winding for a fault to ground. You could have a ground fault part way through a winding.
Bob
davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499
Posted: 12:03am 23 Jul 2014
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Thanks for the hints. I will check it out at daybreak. I should have said it is delta connected ... if that makes any difference.
Cheers,
Dave
BobD Guru Joined: 07/12/2011 Location: AustraliaPosts: 935
Posted: 12:21am 23 Jul 2014
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You would have to separate the windings to get a genuine reading for each winding.
davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499
Posted: 10:49am 23 Jul 2014
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A new day dawns and the light goes on in several areas.
Or with open winding, in a delta configuration, some percentage of those other two phases appear across the non-functioning phase.
Sorted ... thanks again BobD
BobD Guru Joined: 07/12/2011 Location: AustraliaPosts: 935
Posted: 11:11am 23 Jul 2014
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Dave
To be honest, I had no idea what the result would be but , in retrospect, the voltage measurements make sense. The measurement of 51VAC is the sum of the out of phase voltages across the two surviving windings. It's the problem with troubleshooting delta, everything is connected to everything.
Good that the diagnosis was so easy.
Bob
brucedownunder2 Guru Joined: 14/09/2005 Location: AustraliaPosts: 1548
Posted: 11:13am 23 Jul 2014
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Hi Crew,
I fiddled with these little pm motors way back 15 years ago .
two things ,,, they are wound with aluminium wire,so you have to be very clean and careful when making connections -sealing those connections where they connect to copper is very important.
They are very "Coggy" -I removed the rotor and magnets for a look ,very powerful magnets.
Still have one untouched ,,so may fiddle again ..
Bruce.Bushboy
davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499
Posted: 11:40pm 23 Jul 2014
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Bruce,
I disconnected the faulty winding wires where they are tied to the windings so that I could get at the terminations. I then scraped through the wire coating and it was still open circuit. Looks like the wire is broken internally somewhere.
I hope it was a manufacturing fault as I can see nothing wrong externally.
Cogging is OK for the microhydro. Also, there is a copper wire version. I need some spares so don't throw yours away :) We have a local EcoShop where you can usually get SmartDrives so will have to keep a look-out for some Gentle Annie motors there.
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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