Modifying the Stator.

You will need some special items for what follows: some colored heat-shrink tubing (Radio Shack, red, white, blue and black; a small magnetic compass (the smaller, the better); a low-voltage DC source (1.5 volt battery will work); some test leads with alligator clips; some 16 gauge solid strand wire with insulation; and some brass tubing (Hobby Shop, old-fashioned hardware store) with an inside diameter large enough, but just barely, to slip over your stator wires; some cotton string and some low viscosity epoxy glue with a hardening time in hours and NO fillers.

As mentioned in the introduction, the appropriate alternator for this project was wound with bifilar windings, which is to say that two wires were simultaneously wound to form the stator coils. This produces a stator circuit as shown on the left, below, i.e., each of the pole pieces is wound with two parallel windings. These bifilar windings are a nice touch for high-current applications like an automobile, but entirely useless for those of us interested in windmill power. They do present a unique opportunity, however. They can be re-wired to produce the circuit at the right below, i.e., with the pole-piece coils in series instead of in parallel. This single change will double the voltage output from the alternator at any given RPM, and is accomplished without re-winding anything.


This alternator is a three-phase design, with six stator poles for each phase, so there are a total of eighteen poles circling the stator. Actually, when you look at the stator you will count eighteen coils around the circumference, but what appear to be 36 steel pole pieces. This is because the coils are staggered and overlap each other, which you can see when you look closely at them. Theoretically, you should be able to look at the coils and determine how to re-wire them to be in series . . . and I tried to do this twice, but always messed it up somewhere. It's too confusing in there! And besides, there's a better way.

The first thing you need to do is to remove the terminals from the stator coils, being careful to keep track of which wire went to what terminal. The solder used is a very high temperature one, so you may have to give up on heating them to remove the terminals and simply clip the terminals off as close as you can to the base of the terminal and then carefully separate the wires with your wire nippers. Now slip a bit of colored heat-shrink over each individual wire to mark it, using the same color for each terminal's wires. For the purposes of this discussion, put black tubing over the individual wires from the terminal with six wires, red, white, and blue over the individual wires of the other three terminals, respectively. The black wires are the ones from the center of the "Wye" winding, and the red, white, and blue wires are the three phases.

Connect test leads to your battery, red to positive and black to negative. Connect the black battery lead to all six of the black wires on the stator. Make sure all the other leads are separated, and pick one of the red stator wires and connect the red battery lead to it. This will energize six stator coils, and you should now be able to take your compass and identify six poles where the "north" end of the compass needle points directly to the stator wall from the inside. Gluing the compass to a stick makes this much easier. Mark these poles with bits of tape, or whatever. Your marks should be spaced every six steel segments around the inside circumference of the stator.

Now connect the red battery lead to the other red wire, and you should see exactly the same poles you just marked with tape be indicated by your compass in exactly the same way.

Next you must determine which of the black wires are connected to the red wires we are playing with. Separate the black wires and connect one of the red wires to the positive (red) battery lead. Now connect the black battery lead to the black wires one at a time until you get a small spark indicating continuity. You have now identified the negative end (black) and the positive end (red) of one stator coil. Mark them somehow so you don't get them mixed up. Now switch your red stator leads and identify it's corresponding negative end in the same way.

At this point it is a good idea to verify that you can energize either stator coil you just identified and get an identical effect as indicated with the compass. Be absolutely sure to only energize the black terminal with the negative battery lead. Swapping polarity will really confuse things.

Now take the red lead from one of the stator coils just identified and connect it to the black lead of the other one. Depending on which leads you are connecting you may be able to simply slip a short length of your brass tubing over the two ends and fill the tube with solder, or you may have to splice in a short length of 16 gauge wire. After you are done soldering, attach the battery leads to the unconnected red and black wires of your two stator coils and again test with the compass. If all is well, you should get the same result that you previously had with each individual coil, but perhaps with a stronger field. If you do not, you may have to swap the leads you connected to the other pair. After you have verified that all is well, wrap your exposed connections with the cotton string to form an insulating sleave. I suggest this technique because the space adjacent to the stator when the case is assembled is very small and you need to use it wisely. You will be saturating this string with epoxy later after everything is pressed tightly into place.

You now have four remaining black wires, and two each of blue and white. Follow the same procedure as above with each color individually, substituting either blue or white for red and making sure to use the black battery lead (negative) on the black stator leads exclusively. Test at each stage, then test again. You should find that your "blue" stator coils move their north poles, as determined by the compass, two steel segments in one direction, relative to the red ones, and the "white" coils will move the north pole two segments in the other direction. After you are sure everything has checked out properly, and you have left yourself enough wire to re-attach some terminals later, tie everything down as tightly as you can with string to minimize the space used. Put the other case half against the half containing the stator to be sure there is enough clearance, and if so remove it and saturate all of your cotton string with epoxy and set the stator aside to let it harden. Do not use the so-called "5 minute" epoxy, as this stuff is a very poor performer. The best epoxies will take a couple of hours to set, but don't worry, you'll use that time and more with the rotor.

Identifying the Appropriate Alternator.


Modifying the Stator.

Modifying the Rotor.

Assembly and Voltage Regulation.

Resources and Services.

Purchase our Special Magnet.

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