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3 phase but 1 phase low current
By cjdock, Section Wind Posted on Wed Apr 12, 2006 at 05:05:28 PM MST
new windmill, low current on 1 leg

Hi all,
I've been working this winter/spring on my first windmill. I got it completed today. It's a nice windy day as well. The windmill is 3 phase, 12 magnets, 9 coils wound and wired in a star configuration. I have 6'6'' diameter 3 blade rotor. Now that it's up and running, I'm getting 12.6 volts at the batteries. Before the bridge rectifier I measure the current in each leg with an inductance ac current meter. 2 of the legs have 7 amps but the third has only 1.5 or so. After winding the coils I ohmed them out to make sure nothing was grounded and that there was continuity and it all looked good. All three legs should put out the same volts/amps right? Any idea what went wrong?
Chuck

3 phase but 1 phase low current | 11 comments (11 topical)

Re: 3 phase but 1 phase low current (3.00 / 0) (#1)
by picmacmillan on Wed Apr 12, 2006 at 11:19:42 AM MST

hello cj, did you check each coil for resistance...it sounds to me like you have a coil or two in backwards on that weak phase...each coil has some resistance, as we check each one as we go, the resistance should increase, if it goes down, then you have put a coil in backwards(or upside down)..i wind all my coils in a clockwise motion and put them into the stator in this manner, making sure the start and finish wires come off the coil on the same side as all the rest...good luck with your project..pickster
http://www.frecklefarmloghomes.com

Re: 3 phase but 1 phase low current (3.00 / 0) (#3)
by dinges on Wed Apr 12, 2006 at 11:27:37 AM MST

Whether you connect the coil 'normal' or 'backward' has absolutely NO impact on resistance. Negative resistance doesn't exist (unless you delve very deep into electronics; tunnel diodes, amplifiers that are fed back).

However, backward connection of a coil will lower the AC output voltage.

The rest of the diagnosis, a coil in reverse, seems to be the logical problem.

But initially, I'd try to remove the rectifiers and measure voltage/current per phase. That way, you can exclude possible rectifier problems.

Good luck,

Peter.

[ Parent ]

Re: 3 phase but 1 phase low current (3.00 / 0) (#2)
by Flux on Wed Apr 12, 2006 at 11:24:00 AM MST

Wait for a fairly low wind day and take the leads off the rectifier and check the ac voltage between each of the 3 leads. If they are not reasonably equal you have wired something wrong. If they are fairly equal have a close look at the rectifier.

Not so easy to check under wind conditions but it should be possible and it will save you having to take it down.

Another way may be to short the ac leads together and measure the current in each line but for that you will need a good wind to make the thing crawl round fast enough to make reasonable current.

If you find the trouble is in the winding you have most likely reversed one coil.
This would not show on resistance but will drastically mess up the volts in one phase.
Flux

Re: 3 phase but 1 phase low current (3.00 / 0) (#4)
by cjdock on Wed Apr 12, 2006 at 12:32:21 PM MST

ok, now I'm really confused. I have been reading old posts and don't understand how the coils should be wound. 9 coils, 3 phase, and wound clockwise. Starting at coil 1, the outer end wire we can call the tail, the inner starting point wire we can call the head. So I would take head of coil one and connect it to tail of coil 2, then head of 2 to tail 3 then tail of 3 goes to common ground? Or do I need to alternate like head to head, then tail to tail, then head to head again? When I say coil 1, 2 and 3, it's really coil 1, coil 4, then coil 7 as phase one.
Thank for the help...wish I know this before building the stator.

Re: 3 phase but 1 phase low current (3.00 / 0) (#5)
by SmoggyTurnip on Wed Apr 12, 2006 at 12:34:25 PM MST

Head to tail, head to tail, head to tail .....

Also your star point should be all heads or all tails.
The sooner you start the longer it takes.

Re: 3 phase but 1 phase low current (3.00 / 0) (#8)
by Flux on Wed Apr 12, 2006 at 12:59:06 PM MST

Remember you need to lay all the coils the same way. It is far safer to look at the finishes and make sure they all come off the same side. The starts can often be confusing.

You can easily do a check if you have an analog meter. When you have connected all the coils, connect one lead of the meter to the star point and the other to one output lead. Take a magnet and bring it towards each coil of the phase you are connected to. The meter will kick one way as you approach and the other way as you remove the magnet.
It doesn't matter if it kicks forwards or backwards as you bring the magnet near but remember which way it is. Always use the same pole of the magnet and try it over all the coils in that phase. The kick should be the same way for all of them.

Transfer the meter lead to the other phases and repeat. Each coil should kick the same way as you approach it with the magnet. If any coil kicks the other way the coil is reversed.

It is well worth doing this even when it looks obvious that the connections are right.

This is much more difficult with a digital meter but with a lot of care you can still do it. The meter must be set for low dc volts and you ignore the digits, they mean nothing. The thing you must watch is the polarity indicator, usually there is nothing when positive and a negative sign shows when negative. The polarity must always be the same as the magnet is approaching the coil. When the magnet is stationary the meter could show any polarity depending on its offset so make sure you check with the magnet moving.

Flux

[ Parent ]

Re: 3 phase but 1 phase low current (3.00 / 0) (#6)
by kitno455 on Wed Apr 12, 2006 at 12:41:14 PM MST

its head-tail-head-tail.

but that does not really mean inner-outer-inner-outer, as you can still turn one of the coils over accidentally. the outer wrap can be on the right or on the left, which would switch it from a head to a tail...

connect the thing to a battery thru a resistor, and use a compass to find the one you flipped. then dig out the connections and fix it.

allan

Re: 3 phase but 1 phase low current (3.00 / 0) (#7)
by cjdock on Wed Apr 12, 2006 at 12:55:17 PM MST

Thanks for respnding all,
kitno455, I like the sound of being able to repair the stator but am very green to all of this. Could you explain in detail what resistor I would use, and how to connect it to the battery...just so I really understand that. Fixing it will be a lot cheaper than rebuilding it.
Thanks.

Re: 3 phase but 1 phase low current (3.00 / 0) (#9)
by Flux on Wed Apr 12, 2006 at 01:11:42 PM MST

That is good advice from Allan and I will not steal his thunder, I will let him explain.

You can also find the reversed coil by my method with a magnet, but if you have potted the star point you will need to be a bit more careful as also you will have to with Allan's method.

You will now have 2 phases in series so you will have to be careful to check the 3 coils of each phase at a time. The 3 symmetrically placed coils should check out with the same direction kick and if you are lucky you may be able to identify the leads to each coil. If they are all mixed up you will have to test each batch of 3 coils and find the odd one out, then dig into its connections and reverse them. A Dremet tool or a battery drill with a rotary file or carbide burr is good for digging.

Flux

[ Parent ]

Re: 3 phase but 1 phase low current (3.00 / 0) (#10)
by kitno455 on Wed Apr 12, 2006 at 01:35:55 PM MST

more like whisper, not thunder :)

you got a 12v car battery? hook one of your phase outputs to one of its posts.
then hook another phase output to one side of a low wattage 12v turn signal bulb. then hook the other battery post to the other side of the bulb. you have now made a simple current-limited dc circuit that turns 2/3 of the coils in your stator into electromagnets.

you can then use another magnet or a compass to figure out if all the coils in a single phase are pointing the same way. be careful, as flux said, cause you have two phases hot, and they are interlaced with the third, unpowered phase. all coils from the same phase should attract the same pole of a magnet or compass. then move the batter connection to the third phase, and test that one (plus one phase you already tested, it should stay the same)

if you find that one coil in your low amp phase is flipped over, you will have to dig out the connections between it and its neighbors, and flip the connections.

allan

[ Parent ]

Re: 3 phase but 1 phase low current (3.00 / 0) (#11)
by cjdock on Fri Apr 21, 2006 at 05:37:35 PM MST

Thanks for the help all. I found the coil and reversed the leads. It worked but I had to tear up the stator pretty bad to fix it. The genny is back up but we haven't had wind for the last few day :{ ..
I ordered new wire, I'm making a new stator anyways. Thanks again for the helpful info.
Chuck

[ Parent ]

3 phase but 1 phase low current | 11 comments (11 topical)

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