xs alternator windings

[HobbyMan]

Well, since I am miles from home here at college and have no manual or alternator winding, i was wondering if anyone knew how many times the DC field (exciter) coil is wound. Also, If anyone knew how many poles the stator winding had and how many times each pole is wound. I doubt anyone knows this because you have to completely unwind these coils. Also, when the engine is idling, what is the voltage on the wire that goes from the voltage regulator to the field coil. The other wire on the field coil should be the battery voltage. Also, what are the AC phase voltages on the 3 white alternator outputs? In case you are wondering why I want to know:
I am studying electrical engineering and I was just going to do some experiments rewinding coils. I just want to calculate the flux from the exciter coil and perspective voltages on the 3phase AC to find efficiency. Maby one of these days I will be able to figure out a magic replacement that will give these weak alternators a high output. One of these days I am going to build a new wiring harness with the ability to carry a high amperage alternator.

[John]

Did you say a Flux Capacitor, and HOW many jigawatts?

[skids]

She's givin' you all her all she's got Captain!

Originally posted by John
Did you say a Flux Capacitor, and HOW many jigawatts?

[Poprock]

Quiet, you guys! I think the kid may be on to something. (not on something)

[skippy344]

See if this helps

[TopCatGr58]

Hey Hobbyman,

You might want to do some searches on here, because I think I remember reading about someone....possibly GEEZER, who had looked into rewinding the coils, but ran into a room problem, or was wanting to use thicker wire, etc.!?

But I wish you luck otherwise!
T.C.

[randy]

Hobbyman,

I can answer (sort of) one of your questions. The AC output of each phase of the stator should be near 50VAC at 5000 RPM. Have no clue what it is at idle, but I'd guess it's close to nothing!

[HobbyMan]

Those diagrams are helping quite a bit. They confirmed my suspicions on how this alternator works. What I can see right now is that when the system voltage with all of the loads comes above the proper level, the regulator increases the voltage on the green wire going to the field coil. (12v-VOLTAGEgreenwire)= voltage drop on field coil. This gives less magnetic flux to the stator, which in turn causes the voltage on the stator coils to decrease. When the system voltage is too low, it decreases the voltage on the green wire to allow more current to flow through the field coil. This will give more flux and increasing voltages on the stator. I am not sure how different Geezer's reg/rect unit is but I suspect it uses a standard 3 phase bridge rectifier with 6 diodes. I don't quite understand what the extra 2 diodes are for on the stock reg/rect. The problem is that with an XS alternator, the rotor can only "be so magnetic" (magnetic saturation) The purpose of putting a core inside of the coil is that the better ferromagnetic core properties help pass the flux to the stator. AS I understand it, you can only apply so much flux to your core because once the magnetic domains are aligned, your core isn't helping any more. (saturation) I am not going to assume that adding more field coils won't help at this point.

-if your not interested by now- skip the rest
Sitting here thinking about it, I think I devised a test to prove this theory without rewinding anything. Next time I get home, I am going to run the alternator manually by disconnecting it from the engine and applying various voltages across the field coil and measuring AC voltage output. If the stator voltage increases steadily as I vary the field coil voltage from 0 to around 20v, it would be worth it to add some more coils to the field coil. If the stator voltage goes up and stops going up when the field coil hits around 12v, then the rotor is essentially "maxed out" and increasing coils on the field wont help.

Now lets assume that I am going to add field coils, will the stator coils be able to handle the extra amps without destroying the insulation? Second, would the wiring harness be able to handle the extra ampacity? I have a solution that would protect the wiring harness with a secondary rectifier in parallel running alternate loads.

All of these questions will be answered when I get home in a few weeks I hope.

Maby, at this point, it would be easier to put the XJ alternator on the XS. It should provide the ability to handle greater amperes because the field coil rotates, essentially passing more magnetic flux to the stator..

Without knowing the specific turns on the stator & field coil and output voltages, I can't calculate the efficiencies and flux losses.

[lakecountrydave]

I think Poprock is half right. I would be very interested in a mod that increased our bikes ability to run accessories. However, the kid is in college so I a inclined to think he is also in a drug and alcohol stooper The older I get the more I have to belive that Mr Hand (Fast Times at Ridgemont High) was right.

Dave

P.S. Just kidding Hobbyman

[DiverRay]

Hobbyman,
I know for a fact that the '79 will put out over 17.5v! DAMHIK . I think you could increase the output about 15%, but I would try and increase the wire size all the way around. I was boiling batteries for over a year before I found the problem INSIDE my wire harness. I would use Geezers reg/rec, as I think the stock unit will fry.

[HobbyMan]

The problem is that it will put out that kind of voltage wilth little load at high rpms. When you are running lots of lights, a stereo, heated grips, etc.. the voltage drops considerably. You don't realy want the ability to produce high voltage, you want more ampacity.

[DiverRay]

That WAS running at 3500, with all the lights on! I had a short inside the wire harness, and it pumped the voltage WAY up! I was filling the battery every week!

[HobbyMan]

It the green wire is shorted to ground, starting at 2000rpm, the voltage will climb above normal limits. That sounds like what happened. That is a potentially dangerous situation

[planedick]

Been working on it....

I have a friend that owns a business rebuilding alternators, generators and starters for big rigs. I took a alternator to him to look at and we discussed the possibility of increasing the field to get more amperage out of the alternator. He also refered to most control systems that vary the input to the field as a method of regulating the output and it is agreed that more windings on the field would probably increase the output amperage, but not by much as any more would overheat the alternator windings causing failure. It is easy to see that the only way to increase the amps beyond 25 (currently 22) is very difficult as it would necesitate the design of a new frame and laminates to accomodate larger wire and more turns. I am in the process of removing windings and counting turns to see if I can increase it by about 5 - 10%

[HobbyMan]

So basically once we know how many coils there are, the number of turns on each coil, and the gauge of each wire we may figure out whether or not it can be rewound with thicker wire. If we could add more DC field coils and put a heavier gauge wire on the stator.