| This is a continuation of a previous posting http://www.fieldlines.com/story/2004/2/1/0449/36712 where I build on the idea of using a core made from steel wire. The stator is built for a single 4.5" diameter magnet rotor. There are 16 small Neo magnets that are 0.5" diameter, 0.125" thick. The idea was to make a stator with 16 coils to maximize the cogging effects. This way it would be easy to tell the effects of the steel wire cores as I changed their shape.
The first picture shows the particleboard form used to hold the U-shaped pieces of steel wire. The wire used was plastic coated gardeners wire. Not the best to use for a full size stator, but fine for these tests. The core diameters are 0.375" and 14 wires would fit nicely into each hole. I used zip-ties to hold the wires on the opposite side.
A 4.5" diameter piece of plywood was used as a base and fiberglass resin poured. The previous form holding the wires was then inverted and placed into the resin. This holds the wire cores in place as the resin cures. Then I removed the particleboard form and it is ready for the next step.
Sixteen coils were then wound from #28 AWG magnet wire. There are 265 turns per coil. The coils were then placed over the cores. I cheated and used hot glue to hold the windings in place as I removed them from the winding form.
Again fiberglass resin was used to encapsulate the coils. All the wires were dressed out the back so I could easily change the wiring. Looks kind of like a birthday cake!
I use a motor from a ceiling fan to turn the magnet rotor. This motor runs at 480 RPM with no load. This picture is with the wire cores un-cut and coming straight out of the coils. This set up yielded an open circuit voltage of 20 with all 16 coils wired in series (480 RPM). Cogging, as expected, was quite severe. I use an X-Y axis drill press vise to hold the stator so I can change the alignment and spacing.
By the way, it might be fun to use a ceiling fan motor as the basis for a generator for those interested in motor conversions.
Next I folded the ends of the wire cores over to form a "T". This made it possible to form the slots I was after. Once again the output was 20 volts open circuit. Cogging now was very mild by comparison. If fact, there are now 32 cogging points instead of the original 16. When the motor is stopped, the magnets will come to rest right over a coil, or in between two coils.
Since I used very small wire (28AWG), the output was only 1.2 Watts at 465 RPM. Total series coil resistance was a whopping 24 Ohms. It probably would have been better to shoot for a lower voltage and use 20 AWG wire even for this small generator.
One drawback of folding the core wires over is distortion on the waveform as shown in the picture above. It makes it look like a couple of coils were out of phase, but this is not the case. For those interested the vertical resolution was set to 5V per division, horizontal 2mS per division.
I think if had used varnished smaller diameter steel wire (to pack more steel into the core) and larger coil wire, the output may have been able to get up to 5 watts or so. I'm not sure how much power can be had from 16 small neodymium magnets. Not too sure what I proved here, other than it can be done and it does work...
-Bill- |
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