How to rewind a stator from one phase to three phase

[pole7]

How do you rewind a one phase motorcycle stator to three phase? I was wanting to do this since I've been told that three phase is more efficient. I have looked all over motorcycle forums and no one seems to have a good explanation for this question. My stator has six poles and the rotor has six permanent magnets. The stator and rotor are pictured below.
Stator:

Rotor:

I will be using a Honda CM400 regulator/rectifier (R&R), which is a three phase 12v design. The three yellow wires are inputs from the stator. The red goes to the battery to charge it. The green goes to ground. The black goes to the ignition and is used as a reference voltage to control the output of the regulator.
R&R:

I know that this regulator can be used with single phase by connecting the two stator output wires to only two of the yellow R&R wires.

I know that winding it for single phase would require you to start at 1 with a clockwise (CW) winding (I guess it doesn't mater what direction to start in as long as you alternate). Then move to 2 and wind it counter-clockwise (CCW). Then move to 3 and wind it CW and keep alternating to the last pole. Then connect the beginning of the magnet wire to one of the yellow R&R wires and the end of the magnet wire to another yellow R&R wire. The last R&R wire can be ignored.

If I wanted to wind the stator for three phase would I just need to start at pole 1 and wind it CW then pole 4 CCW? Then with a second wire I would start at pole 5 and wind it CW and then pole 2 CCW. Finally with a third wire I would start at pole 3 and wind it CW and then pole 6 CCW.

In order to wire it in a wye arrangement, would I then do the following?

Wire the beginnings of each pair, which would be at poles 1, 3, and 5, together. Then wire the ends of each pair, which would be at 2, 4, and 6, to a corresponding yellow wire going to the R&R.
Like the image below:

Would this even make sense since my stator would only have two poles for each phase and 180degrees between poles? Do you need more poles to get efficiency benefits from a three phase stator? Would you also have to change the number of magnets in the rotor to make this work? Would it make more sense to just wind the stator as one phase? The only variable I can easily change around is the stator winding, so what do you guys think?

Thanks for any help/advice,
Simon

 

[Motorwinder]

You can't rewind it to 3 phase. To get 6 pole, 3 phase, you would need 18 groups of coils space 120 degrees apart. Can't be done with that stator.

 

[waross]

Beg to differ.
That looks like a three phase alternator already.
Color the red wire yellow.
Color the green wire yellow.
Color the blue wire yellow.
Now you are good to go. Connect it to the three yellow wires on the regulator.
A single phase stator will usually have two coils. you can reconnect a three phase alternator for single phase with a one third loss in capacity but you generally can't reconnect or rewind a single phase motorcycle alternator for three phase. It has to do with the number and spacing of the magnets and the coil positions on the stator.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[pole7]

Waross,

The MS-Paint drawing I made is my plan to rewire from one phase to three. I just used the various colors to help differentiate between each pair of coils. The stator is currently wired as single phase, well actually four coils are used for battery charging and two get turned on when the headlight is turned on.

You said that you can't rewire single phase to three phase due to the magnet spacing. I thought that magnet spacing was more important for electric motors since if the magnets are alighned with the coils then then you wont be able to get the motor started. So would it be possible to convert my six coil single phase stator to three phase using the linked MS-paint drawing?

 

[pole7]

Motorwinder,
Is the 120 degree spacing only important when trying to make 60hz power? Does it matter in this application since I am just trying to produce current that will go into a regulator/rectiifier that will just charge a battery?

 

[waross]

I was wanting to do this since I've been told that three phase is more efficient.
Define efficiency.
How much more efficient?
If you consider energy out over energy in there may not be enough difference to worry about.
Why would a set of coils be used only when the headlight is on? That may be because the alternator is already putting out as much as the regulator can handle. Early Hondas left the headlight on at all times and had a distressing habit of destroying indicator lamps and blowing fuses if the headlight failed. Without the load of the headlight the regulator was unable to hold the voltage down at high RPM.
As the speed of rotation increases the open circuit voltage of a motorcycle alternator increases proportionally. The voltage is controlled at higher RPMs by wasting power. A higher output alternator means more power wasted at higher speeds. That may be why one of the three phase coils is only used when the headlight is on.
By the way, your picture shows a three phase stator with 120 electrical degrees spacing.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[electricpete]

coil groups in a typical 3-phase industrial motor are 60 electrical degrees apart.
That is 60 * (2/poles) mechanical degrees apart.
For 6 pole winding it would be 60*2/6 = 20 mechanical degrees apart
Since it is 18 groups as MW mentioned, 20*180 = 360 mechanical degrees.

Ok, so this would not be standard, but would it work?
I say no.
Your rotor has 6 equally spaced magnets of alternating polarity.
Your stator have size equally spaced stator coils.
At the moment in time when peak voltage is induced in one coil, peak voltage is induced in all coils (possibly opposite polarity). So imagine this is a generator. The relationship between coil voltages is 0 or 180. How are you going to connect them to produce phase relationship of 120? You can't. If you take this machine and hook it to three phase power source, it's not going to work and (not trying to be overly dramatic but...) people or equipment may get injured in the process.

=====================================
(2B)+(2B)' ?

 

[electricpete]

Sorry, I thought you intend to use it as motor, now I see generator. Same answer though... I don't think it will work because your stator coil voltages are all 0 or 180 degrees out of phase... you can't produce 120 (or 60) degrees phase difference from that.

=====================================
(2B)+(2B)' ?

 

[rhatcher]

Motorwinder and Pete are right. It is physically impossible to make a three phase alternator with those parts. You would need a new stator with 18 coils to produce a 6 pole three phase alternator using the existing 6 magnet rotor. Or, you would need a new rotor with 2 magnets to produce a 2 pole three phase alternator using the existing 6 pole stator.

With respect to efficiency, I'm not sure that you would realize any greater efficiency (ie. input power/output power) with a three phase design. It is true that a rectified three phase system will have smoother DC output but, for charging a motorcycle battery, there would be no measurable benefit.

 

[pole7]

Great, those were the answers I was looking for. I figured there had to be more to converting from one to three phase than just rewinding the coils. Magnet spacing explanation was especially helpful. I'll just keep it single phase. Thanks again! Du

 

[waross]

If you remove some of the magnets so you are left with a single north pole and a single south pole opposite each other you will have a three phase alternator. It probably won't be nearly as efficient as the single phase arrangement.
But remember; A motorcycle alternator has no control. The voltage increases as the speed increases. The regulator controls the voltage by wasting power, both in the regulator itself and in the alternator windings. More output means more waste. Not the way to efficiency.

Bill
--------------------
"Why not the best?"
Jimmy Carter