PM Alternator
For my Wind Power, I use a modified car alternator. Its a GM type as they are very cheap and you can find them everywhere! First of all take it apart, then strip everything from the back of the unit, everything. Save the diode pack as you will use this later, just not inside the alternator as we want the AC voltage from this unit, it has less loss up the cable this way.
Before
After - all extra stuff removed :)
The next step is probably the most complicated, but what you have to do is remove the winding from the stator. This is done by pressing the shaft out of the unit and toss everything including the contacts for the brushes. Then you have to find a ring magnet large enough to replace the old coil size. I currently have a N38 ring magnet in my units, so I have wondered if N40 to N45 would increase my output.
Center coil removed. At this point, if you are going to make it easy, is when you put the ring magnet in, then press the fingers back together. A N38 ring magnet or stronger is what you need. Make sure the two faces are the opposing North and South. Measure the shaft to the alternator you have, and use as the "ID" (inside Diameter). Then for the "OD" (outside diameter) measure to the outside before the fingers start the curve. Thickness should be how ever far the fingers press together, and still allow space inside between the two sets, or measure the coil that is removed for height.
Below is a picture with the field coil replaced with the magnet, then pressed back together and all the extra's removed. You can see the magnet between the poles.
Now to build a stator that has more voltage. My windmill is a direct drive unit and with this you have to build the permanent magnet generator to handle lower RPM's. if you leave the stator stock, they are good for connecting an engine to drive it.
I have tested a stator with 15 windings per coil to date, but for this one I want to try a total of 18 winding per coil.
The best way I have found to clean the existing winding off of a stator is to cut one side of the wire that is already on it. Once you have done this you can just pull all the wires out with little effort.
A clean stator!
Oh, now the fun begins. This part takes a bit of time, and patience, if you have none, you don't want to start this project! I used to wind the wires on the stator directly, but I have found its way to awkward, so I have a little tool I have built. The are older pliers that stick open, and with a small amount of force they will shut. I use them to wind each coil, then when done I close the pliers and that lets me remove the coil from the pliers. I place tape on them to hold the coil together until I install them into the rotor.
This works pretty good!
There are 7 coils, 3 fields in total (3-phase) ahh, finally done winding.
When you install the first field, it has two spaces in the middle of each coil, also the outside of each has two spaces also.
when you install the second field, notice, top left is the start, but you start with one space before the next field, then keep the two spaces between the coils again.
I am done, sort of, just have to solder some leads, then coat it, but it looks pretty good so far!
Testing will be very soon, and I will post what I see for output. I test it on the drill press at 600 rpm, and the last unit with 15 winding per field was 13.8 VAC output. I wire it in star configuration, but usually I put all 6 leads out the back so I can change from star to delta if I wish. The last unit when I would short the remaining 3 leads (output) it would stop my drill press due to the load. we shall se how this one will do!
So as you see, as in the picture below, this is a simple system, other than the stator. Remember, if you are just using it for a generator driven by a motor, you can keep the stock stator. As you see in the picture below, these are all the pieces you need, very simple, and maintenance is very cheap as the only thing to go wrong really is the bearings maybe.
Remember, the magnet will last a very long time, but keep the heat of the unit below 185. If you do this, it will last an extremely long time, allot of power generated from that puppy.
This is 3-phase, about 400 Hz, give or take. It depends on the rpm the windmill is doing. I have seen 50 Amps when the wind is strong, and only 5 Amps when its about 25 Km/H. That is why the next one is 18 windings, to try to bring the lower amperage up a bit when wind is low. I am hoping for about 10 Amps. We will see if the coil burns out at higher winds.
How simple! These are all the parts you need for the PM alternator.
This is a finished unit, note the three wires from the alternator. These are just attached to the three wires from the coils and then run directly out from the back. I run 3 wires from my wind-mill down to my shed, then I use the diode pack to convert it into DC voltage. I find that this unit puts out about 40 VAC with up to 80 AMPS maximum with my current windmill. On average it will put out 10 Amps to 50 Amps. I used 1/0 gauge wire.
Heavy duty Full-wave rectifier
As you can see from the picture below, this is my homemade, or rather a modified full wave rectifier. This is the one that is removed from the alternator housing. The metal that mounts this unit will provide additional cooling. This gets pretty warm as 50 to 80 Amps generates quite the amount of heat. I had to add an additional fan that blows through the end of the box. The metal I used for this is aluminum and I also mounted the unit with heat-sink compound between the rectifier and the aluminum. This unit works great with no issues to date!
I have a better idea. I am going to build a stator with some little PM's that I can get off the internet. My hopes are that if I can place the magnets so the directly face the edges of the stator, I will get rid of some of the losses associated with trying to magnetize all the way through the metal fingers. This will be an easy build as once the coil in the center is removed, all you have to do is drill each finger with a 10mm drill bit, and press the cylindrical magnet into it toward the center shaft.
I might even sell these online once they have been tested so stay tuned!
I ordered my magnets today in May 2005. The people whom I ordered them from seem so nice to deal with, and very fast at my emails. They shipped also the same day. Its so rare these days to find someone who is so nice to do business with and I would suggest that you use them for all your magnet needs.
I ordered these
CYL0375
I will post my testing with my new idea for the PM alternator and my results. Keep checking. I am very excited to try my idea, and if it works it should be easy for everyone to build a PM.
I got the magnets. I have to say it was reasonably fast via mail. Super Magnet Man sure packed these very well and they had no damage to them at all. I am impressed.
Now we shall see if this will work. I am wondering if I place these magnets so the surface is directly to the coils in the alternator, and being N50 if it will produce as much power as the ring magnets. I am concerned about the size of the magnets being a bit small but lets see.
What I did here is I wanted to mark the middle of the fingers the best I could. So I used the 1/2 of the alternator housing with the bearing for the bottom, and put the top in my drill press. I then spun the core and marked it with a hacksaw blade. Notice the line on lower right picture.
You cant really see it in lower left, but I then used a punch to mark each spot to drill.
Ready for the Magnets.
Ok, I got this project done. sorry for no more pictures, but when I tested the magnets were to small. I was in hopes it would work because of the N50 strength, but they are physically too small. so, back to the original plan, ring magnets, they do work at N38.
Gas generator "PM" alternator
Success with ring magnet for gas generator, it works better than I expected. on this unit, I cut each hole a bit larger. I didn't want to remove too much material because I wanted the center bearing housing to keep its strength. you will also notice around the diode pack I enlarged the hole also.
usually I remove the diode pack, but this unit is for my homemade generator that runs with the honda 5 hp motor. I wanted to keep everything on one unit.
picture of back of unit
picture from the top
another picture from side
notice here, I spaced the cooling fan with as little clearance as possible. I am trying to seal the blades against the housing as much as possible to increase the air-flow from the fan.
unit mounted and ready to go!
complete assembly
this is working better than I had thought. at half the RPM that I used to have the motor set to, it produces the same output. put it this way, it is exactly twice the power from the first alternator I used to use, that was just a normal alternator, not a PM.
I have to keep the motor running pretty low, and it puts out 60 AMPS. it keeps fairly cool, and on a normal day outside (not exactly sure of temp), the alternator hit 175 degrees. I could still touch it with my hand. the old alternator, used to get way hotter and you could not touch it. I think the extra cooling made a difference!
so on the small tank on the motor, once filled, it will charge at 60 Amps for 4-5 hours. I don't use that much when I am running things in the house, so it is more than enough to keep ahead with charging.
Homemade gauss meter
I think I am going to try to build a gauss meter also. This is used to test magnetic strength and with it I can easily test to see if I have improved the output of the stator.
I found this site on the internet on how to build it. From the Schematic its too simple not to try it out!
