An upgraded simple three phase generator design.

After my failed attempt at getting an output I deemed acceptable out of the simple three phase generator I built I went ahead with a redesign. Instead of four large disc magnets, I used 8 smaller block magnets. Instead of six 500 turn coils I used twelve 200 turn coils. Once again I used 30 gauge magnet wire.

This generator becomes a rats nest of wires and is therefore less simple than the previous version. Still, it can be constructed fairly cheaply without expensive tools.

The first step was to wrap the coils. This time I wanted coils just barely larger than the magnets which would be rotating. Therefore I decided to wrap wire around the magnets. It is very important to wrap the wire in the same direction for every coil, and remember which way they are. If you flip the rotation on the coils, it will dramatically lower the output of the generator, perhaps even to no output at all.







After making 200 turns around the magnet I did one more turn where I wrapped the wire around the coil to hold the wire in place.

Once all twelve coils were constructed, I mounted them on a CD with super glue. This is the step you need to be careful that all are placed in the same orientation. If you install some upside down wiring the generator will become a real mess. It is also important that all the coils are evenly distributed. One coil should be at 0, 30, 60, 90, 120, 150, 180, 210, 240, 270, 300, and 330 degrees. Here is them just before I glued them.



Positioning the magnets was done on a saw blade this time, rather than the CD used in the design I based this on. This is for two reasons. The saw blade being steel acts as a backing iron and helps direct the magnetic fields through the coils it also is a little easier to rotate than the CD. I assume this generator would work with a CD, but would produce a little less power.

Similar to the toys from trash design a large washer was glued to the top and bottom of the hole in the center of the saw. A toothpaste cap with a hole drilled in it was glued to the top of the rotor. The magnets were placed at 0, 45, 90, 135, 180, 225, 270 and 315 degrees which was made easier by the holes in the saw blade. Once positioned they were glued in place, although I am not sure that was necessary with how strong the force between the magnets and saw was.

As before the magnets must alternate. The magnets at 0, 90, 180, 270 degrees will all have north pole facing up when the magnets at 45, 135, 225 and 315 degrees are all have north pole facing down.



This time instead of iron filings, which were quite a bit of work to collect, I decided to use steel wool for the cores of the generator. I simply cut up the steel wool into small pieces then mixed it with wood glue before filling the cores with it. This didn't seem to be quite as good as the filings, but it clearly performs the basic task.

The next step was wiring, which requires some thinking. A good description of the theory of wiring such generators can be found here. For this generator it was necessary to connect 4 coils together to make each phase. The coils at 0. 90, 180, and 270 degrees make up one phase; the second phase consists of the coils at 30, 120, 210, and 300 degrees; while the third is made from the coils at 60, 150, 240 and 330 degrees.

The coils must be connected together so the current adds rather than subtracts. First for each magnet you connect the low side of one coil to the high side of the coil on the opposite side. which side you declare to be low is arbitrary. I decided I wanted the right side wire on each coil to be low. Once you have connected each with the opposing coil, you need to connect the low side of one group with the high side of the group perpendicular to it.

I made some simple sketches showing the wiring, first of one phase, then of all three phases combined. Notice that the low side of all three phases gets connected together. That is where neutral connections are made. This makes it a typical Y connected generator, leaving me with three phases neutral. I could have done a delta connection but I wanted to have the neutral.








This time I decided not to use the sewing machine bobbin for a rotor. It just allowed too much wobble, making it too difficult to get the distance between the magnets and the coils as small as possible. So, I decided to glue a nut and washer together. I then placed additional nuts and washers in place to adjust the height. The rotor then simply rotated on a washer which I lubricated with WD40.







This generator worked a better than the previous version. It produces about 1 Volt phase to neutral, and 1.7 Volts phase to phase. I can light LEDs by connecting an it to any 2 of the four wires.

Still, the rotor could be a lot better. Two washers rubbing against each other do not exactly make the most efficient bearing. I will be keeping an eye out for a way to mount the rotor in a lower friction manner.
Another step which could be done to improve the generator is a backing iron on the coils. So far I just haven't found an easy way to modify this design to allow that. Unlike the backing iron for the rotor, the backing iron for the coils cannot be solid iron. Doing so would create eddy currents which sap the efficiency of the motor. So I would need to make a laminated steel or iron filing based replacement for the bottom CD. Nothing simple comes immediately to mind.