# AC alternator & coil winding connections & theory

Discussion in 'General Electronics Chat' started by enduro250z, Jul 29, 2010.

1. ### enduro250z Thread Starter Member

Jul 6, 2010
69
0
First off I hope ive posted this in the right section.

I am having a little trouble determining the connections of this simple AC alternator. This is the stator and a rotating rotor with magnets spins inside producing AC current. There is no field coils or brushes.

This stator has 3 wires, 2 yellow and 1 red and Im let to believe that there is 2 separate circuits/coils/windings and that one end of each winding is connected together to the red wire which is a center tap I have shown this in my drawing A. The information I can seem to find on this alternator is suggesting that the 2 circuits are out of phase and the output on each yellow wire is not in synch and the 2 can not be connected together. I dont know if that makes sense to you at all. I have also heard that the voltage between one yellow and one red center tap wire is 35 volts AC but you cant just use the second yellow wire to get the full 70volts as the second one will cancel the other one out? The only thing is that when ive heard this people have been discussing connecting it to a regulator rectifier and converting to DC and not AC.

When in AC there is supposed to be 90 watts on each separate yellow wire if you wire each on to a separate AC regulator and keep the circuits separate. I was told that if you connect 1 yellow and one red wire and leave one yellow unplugged, you can get 150-160 watts (not sure if they really mean 180W). But this does not make sense if the red wire is a center tap as essentially your not getting the output from the second winding so I believe I was given wrong information here.

I have shown in diagrams B and C 2 ways I thought I could connect it to a AC regulator in series or parallel, but since Im led to believe the stator is out of phase Im dont think this would work combining both circuits together like this in series or parallel and I dont think sure I would get the full output together? If this wont work then I believe I need to make the alternator in phase

As I understand it, having different phases is due to having the coils wound in different directions (CCW, CW) to the others??? There is 14 poles so I assume 7 are wound CCW and 7 CW and this makes the 2 circuits of 7 wound poles produce the power in 2 phases?

Anyway, what I want to do is get the full 70 volts which is ment to equal somewhere from 150-180 watts when regulated to (12-15 voltes AC), out of the alternator at the one time. To do this I think it has to be converted so the 2 circuits are in phase but Im really not sure. Now I reckon what I need to do is to basically flip the connections of one of the windings around. I have shown this in diagram D I have left a little bit of red and yellow on each end of one of the windings so you can see I have swapped that windings connections around. If I am correct, I have now converted this to producing the full 70 volts in phase?? Im not really sure though as the wires would still be wound the same on the poles, its just that Ive changed which end is attached to the yellow lead and which is connected to the red lead.

Assuming ive now got the 2 circuits working in one phase, now one way to connect it would be in series as shown in diagram E. One yellow to ground and the other into the AC regulator and the red wire is not connected.

The second way is to connect it in parallel as shown in diagram F.

Now I always believed that connecting 2 coils or windings in parallel will give you the most output but Im not really sure. The big question is, which way is going to give me the most power series or parallel?

I have tried searching the web, wikipedia etc for this sort of stuff but can never seem to find anything that simply answers my question exactly in an easy to understand way. I just want to finally know once and for all how this works! I will keep trying to look though.

Thanks for your help.

2. ### SgtWookie Expert

Jul 17, 2007
22,182
1,728
Here's what you need to do:

The yellow wires are equal in amplitude, but 180% out of phase with each other.

The rectifier diodes take the split-phase AC, and change it into rippled DC.

Look in our E-book under "bridge rectifiers".

From there, you can add a capacitor to reduce the ripple content. How much capacitance you will need depends upon what your load current will be, and how much ripple can you tolerate on the unregulated DC portion.

Since we don't know what you're planning on doing with this yet, talking about voltage regulation methods would be premature.

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3. ### enduro250z Thread Starter Member

Jul 6, 2010
69
0
I dont need/want to rectify it. I know it is possible to do it in all AC though. Cant i just flip the connections of one winding/coil around to get both in phase and then either run the coils in series with no red wire connected or in parallel like my drawing?

4. ### SgtWookie Expert

Jul 17, 2007
22,182
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Well then, you'll have to replace all of your lights with 28v lights. Is that what you'd like to do?

I don't know why you don't wish to rectify the output. That's how it's normally done.

If you attempt what you're thinking, you'll need one heck of an AC regulator circuit. It won't be a lot of fun, and I won't be working on it.

5. ### Aule Mar New Member

Jul 27, 2010
4
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I'm guessing what you want, is to get 120 v AC single phase out of the it!? Can't be done, what you can do is to set it up like it is in a car, that is generate 14.5 volts 100amp or there about feed that to a battery
to maintain 12V and connect an inverter to the batters to get your 120V at 60 cycle.
The three windings are set up (mechanical allignment) to create three AC currents each 120 dergees out of phase from each other. No mater how you tie them together there going to be fighting one and other at some point in the rotation of the roter.
Aule

Jul 17, 2007
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7. ### enduro250z Thread Starter Member

Jul 6, 2010
69
0
I will try and go back to square one here then work out how I want/can connect it. Assuming what ive heard is correct and this 3 wire stator is out of phase How would it look? I dont really know if it is one continous winding like diagram A with the center wire tapping halfway through the winding.Or if it is 2 separate windings lie diagram B??

Now im going to assume its 2 separate windings like diagram B As we believe this is out of phase (180 deg apart????) is it going to look like diagram C or diagram D?

Now im guessing, to get the 2 different phases, that one winding is wound one way and one is wound the otherway and to make the 2 windings produce power in phase both sets of windings need to be wound the same way or have I got it around or have I got in around the other way and inphase the 2 windings are found different and out of phase the 2 windings are wound the same??

So which one of my drawings is in phase, C or D? And to get it in phase do I just swap the connections of one set of windings around the otherway?

At maxium revs flat out at about 9000 rpm for example. The alternator supposedly makes 180 watts or 90 watts from each yellow wire but not in phase. Realisitcly I believe it only makes a usable 150-160 watts all up, but we will assume 180w. Assuming I can get the full 180 watts out on 2 leads and in phase and either running the 2 windings in series or parallel, with no power consumed (lights off during the day), the AC regulator needs to be able to handle shunting 180watts. Now that is no problem because you can buy regulators rated for 200 and 225 watts. So there shouldnt be a problem there. I just need to work out how this stator is wired to be out of phase and if it is just as simple as changing the connections of one set of windings to get it in phase and then get the full 180 watts out in synch between 2 leads (series) or parallel which is 2 sets of 2 leads.

Last edited: Jul 29, 2010
8. ### enduro250z Thread Starter Member

Jul 6, 2010
69
0
No i dont want to get 120 volts AC out of it. For all purposes of this exercise, just assume that its making 90 watts at 35 volts on each yellow wire and then we regulate this to 90 watts at 14 volts with a AC regulator. In short i want to run a 130 watt 12 volt halogen light off this alternator with AC. Absolute max on each winding is 90 watts so using one circuit is no good, but if i can link the 2 circuits together for single phase then im good to go.

Rectifiing to DC will instanly produce a loss of about 25 - 30 % or 1/3 of the original AC watt rating. So if its 180 watts AC, after full rectification i would only be left with about 120 watts to work with or 60 watts on each circuit and thats at teh very most. The general consensus is that these stators make 150-160 watts max usable power and 180 is only when the RPM is full on flat out.

Well yes they are off a Ducati but from older 70's, 80's models. The ones that had problems were around 1998 when they upgraded to a 300- 500 watt alternator which was 3 phase i think.

Anyway, this is not going on a Ducati anyway, People use these small alternators as add on's to the end of the crankshafts on trail bikes and MX bikes to supply more power. These particular 3 wire 150-180watt stators were not known to fail, they just had a low output at low RPM and struggled to keep up charging a battery.

There is now a company who is making these in aftermarket verson which are a 2 yellow wire output single phase unit.

Last edited: Jul 29, 2010
9. ### enduro250z Thread Starter Member

Jul 6, 2010
69
0
I found this link which looks like it has some useful info but im still struggling to work out what i have/how do what i want.
http://www.ibiblio.org/kuphaldt/electricCircuits/AC/AC_10.html#02170.png

I am begining to wonder if all i need to do is leave the red disconnected, run one yellow to ground and then the other yellow to the AC regulator and then get the full output of the stator in one go and i dont need to change any connections around since im going AC? If going to a DC system then i reckon i would need to do what i have shown in diagram 'D' in the very first attached diagram in this topic/thread.

I think i have got something kinda like this or this is what i sort of need to do.

Last edited: Jul 30, 2010
10. ### SgtWookie Expert

Jul 17, 2007
22,182
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I think that you are overestimating the losses in the rectifiers.

Download a datasheet for a Motorola/ONsemi MUR3040PT. This is a 30A 400V dual diode in a TO-218 case.
Datasheet: http://www.onsemi.com/pub_link/Collateral/MUR3020PT-D.PDF

Let's say that you had 5A current being output from each of the yellow wires. At 5A current, that diode would have a 0.7v forward voltage drop. If your output was 25v peak, that represents less than 3% power loss; not very significant.

If you tried wiring the magneto/generator so that it was in series, you would double the voltage, but cut the frequency in half. This makes regulation at low speeds a problem.

Last edited: Jul 30, 2010