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Dual Rotor Toroid Core PMA build
DanG:
The dry heat of AZ primed everything that could be primed into being ready to corrode. Once the introductions are over the oxidation should slow down enough to not keep you awake at night with the sputtering noises and dull red glows...
It'd be interesting to see if a substitution to a solid plate vs. the wound laminate would change outputs?
SparWeb:
Craig,
No pressure. Didn't know you were moving. I wish you the best with all the new possibilities in your new home!
It's vaguely possible that a thin layer of corrosion will be helpful - only insofar as it isolates each lamination, but since the subject of Nomex interlamination sheets came up, it won't matter at all. Or you could do without the Nomex at all.... ha, that's the evil Sparweb talking there. You don't want any rust and especially not moisture in the laminations or it will eat itself away from the inside.
--- Quote from: DanG on August 08, 2012, 05:16:57 PM ---It'd be interesting to see if a substitution to a solid plate vs. the wound laminate would change outputs?
--- End quote ---
Probably a big detriment. The eddy currents increase their drag in proportion to their size, read: diameter. When induced through the thickness of a sheet then the diameter of each eddy can't be larger than the thickness of that sheet. Eg: 1mm sheet -> 1mm eddy diameter.........but........... 12mm plate -> 12mm eddies. Square the number for the area, and the result is a 144 X greater iron drag force.
(I think you're supposed to square the number to compare eddy-current forces; correct me if I'm wrong).
CraigM:
Holy crap! Seven years since I started this post!
I always wanted to finish this PMA but life gets in the way. Mostly from a house renovation that took better part of five years. Bought a house built in 1960 and striped it down to the frame, only thing left was brick exterior, oak floors and frame. All new electrical, plumbing and insulation when in. It's small at 1500 sq feet but very efficient. Heating and cooling done by two small mini-split air conditioning / heat pump. A one ton on one end of the house and 3/4 ton on the other. Total electric, utility bill averages $100 a month.
So back to this PMA. I live in a poor wind area so it doesn't make sense to try and make this thing fly properly. I live on eight acres and have a five acre open pasture but it's surrounded by tall trees. Best I can think to do is "cringes" make this a yard art project, maybe something like a Lenz 2 savonius.
The PMA is patterned after the 2.5 Proven design. Not much info on the internet for this type of PMA but do know the Proven 2.5 uses two eight pole rotors and a 24 coil, three phase stator with a toroid core made from wound electrical steel.
Hugh Piggot talks about his time working with Proven on his YouTube channel. See link below at 8:30 into video.
https://www.youtube.com/watch?v=S5phDyk4590
So I'm at a point where it's time to wind a test coil and wanted some input as to how to measure current and test the PMA.
Here are some update photos:
This is the test platform built to hold the spindle. Sandwiched the spindle between two 2x4's put under pressure. Built additional 2x4 frame and covered it top and bottom with 3/4" plywood. Ends are open so I could reach inside to fix threaded rod for mounting the stator.
I'm only allowed 5 attachments per post to will end this and start a new post.
To be continued ~
CraigM:
Continued ~
The rotors are 11.5" diameter, .25" steel. Magnets are ferrite, 3" x 2" x 1" thick. Magnets were purchased as 2" x 6" and I cut them in half with a diamond blade on a tile saw. It's slow going but works well. If I had to do it again it's possible to cut a wedge shape from a 4" x 6" block and cram in more magnet material. Magnets are N - S - N - S on the rotor but will be oriented N to N and S to S when facing each other. With 12 square inches of magnet material per pole and a cross section of .625" x 2" (1.25 sq. in.) on the steel core, I believe this is called a flux concentrator. Hugh talks about this in the video posted earlier.
The last photo in the series above shows some 1.25" fiberglass material I will wrap and glue around the perimeter of the rotors. I will tack it in place with Cyanoacrylate (CA) glue and then use thinned epoxy to wet it out and attache to magnets and rotor edge. You can use rubbing alcohol to thin epoxy. Believe this will add a bit of strength to keep the magnets from flying off at high speed... they are quite heavy.
To be continued ~
CraigM:
~ Continued
Next are photos of the stator and some of the issues that came up. When you're building something you've never done before you tend to take aim and give it your best shot. Sometimes you hit the bulls eye... most times you don't.
As shown much earlier in this post I started with a wound steel core. I had access to the material and after seeing how the Proven design was made it was a "why not" decision. Next came the spokes. I had access to G10 epoxy/glass laminate and was comfortable working with this material so I chose to cut these to size and glue them to the laminated core using JB weld. Electrical paper, can't remember the name of it, was used to insulate the steel core
You'll see in the photos I cut the spokes a bit short and had to add a filler piece (aircraft plywood). I also added a thin 1/16 filler piece on the inside of the spoke... will comment more about this later.
The last two photos show the addition of of a half round flexible molding piece I added. I tried a test coil wound over the square edges of the core and found the wire did not want to lay flat on the core. By adding the rounded relief the wire isn't require to make such a tight bend and is much easier to wind. This took up space however and is the reason why the spokes were now too short.
I used CA glue to fix the filler piece, plywood bits and the molding. As long as the parts are sanded to give them some "tooth" and they are close fitting with no gaps this is a quick way to glue up a bunch of small pieces.
To be continued ~
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