Mock up dual rotor-would like opinions

[Reno]

Hello everyone

I bought my 3/8 inch 1018 cold rolled steel and will attempt to cut in so I did a mock up of the layout. I was wondering if anyone sees any problems or mistakes.

It will be a 10 inch rotor with 8 magnets. The paper in the pic represents the coils with the magnet shape drawn on them for reference.

One othe question I have been tossing around the ides of making 3 stator plates then stacking them for 3 phase is this worth persuing or should the legs of the coils be as close to the magnets as possible meaning over lap is required.

opinions appreciated

thanks

[picmacmillan]

hi there...what size wire you using..also are the coils big enough so that they touch each other?...hard to tell from the photo..coil resistancemight count...also you have 8 mags and 8 coils?...pickster

[Reno]

The coils will be wound to suit. in other words I am going to make test coils so no second guessing. I have eight magnets and eight coils becasue I am going with the conventional 3 phase setup. as for the coils big enough to touch each other I not sure what you mean but the lead leg of the second coild rests over the center of the first and the same with 2 and three. When the magent is over the last coil the lead leg of the first will be over the next magnet.

[baggo]

Hi Reno,

Just my humble opinion but it looks as though your coils will not be wide enough to get the most out of the magnets. Most people suggest that the coil span (distance between the centre line of each leg) should be equal to the distance apart of the centre line of the magnets. Then one leg will be over a north pole and the other over a south pole and the maximum voltage will be induced in the coil. To ensure this with your proposed set up would make the coils very wide and there would probably be a lot of dead copper in the tops and bottoms of the coils (assuming you keep the hole in the coils the same size as the magnets). The coil sizes you show would probably be about right if you used 12 magnets per rotor instead of eight or reduce the diameter of the rotor to say 8 inches. You will possibly have to increase the length of the coil legs a bit as well if you intend to use overlapping coils to give a bit more wire to bend the top and bottom of each coil out of the way of the next. You could do as you suggest and make three flat rotors and put them together but then the finished stator may come out too thick.

John

[Flux]

I don't follow what you are doing.

8 magnets and 8 coils  gives single phase.  For 3 phase you need 6 12 or 24 coils.

If you plan to stack 3 single phase stators on top of each other with 24 coils total that will work as long as you space them round 120 electrical degrees.

I can't see any virtue in this method, I would stick to a 6 coil single layer stator or go for the complexity of using 24 coils overlapped and then they would be similar to your paper drawings.

Flux

[windstuffnow]

   Reno,

     I think alot depends on the thickness of the coils after their stacked.  It's best to keep the gap between magnetic rotors as small as possible to achieve the highest output.

     You could do it a few different ways...  An 8 pole / 6 coil arrangement - the coils would be fairly large and waste alot of wire.  8 pole / 12 coil arrangement - less waste, better power, thinner coils.  Or as you stated the 8 pole / 24 coil arrangement - a little more difficult to wind but you'll have smaller/thinner coils, less waste and more power overall.

      All of which is determined by the power your looking to get out of the unit as well as the space your limited to for getting the coils in place.

      You could probably get by using a smaller diameter thus reducing the size of the coils even farther to increase the output.  Here again it depends on the power your looking for as well as the cut in speed your trying to achieve.

      For the most part the layout looks good and your well on your way.  

Have Fun

Windstuff Ed

[Reno]

Hello Flux there will be 3 sets of coils each set containing 8 coils

[Reno]

Hello Baggo each paper mock up represents a layer of coils or a phase so the first layer is centered over the magnet. The second layer has one leg over the maget and the other over the gap and the last has the trailing leg over the magnet and the leading leg over the gap. Each leg is approx. 1/2 wide and the center of the magnets are 1 inch wide. I have 16 magnets so there a 8 magnet rotor X2 is not a variable.

[Flux]

Reno

That's fine, but as someone else pointed out you will have to increase the coil leg length to get them to overlap. You need to end up with one coil thickness in the gap and do the overlap at the ends by bending alternate pairs of coil ends or else hand wind them into some sort of former as Windstuff Ed does.

If you make the coils as shown in the sketch  you will take up the same space as 3 single phase stators stacked on top of each other and loose the benefit of the 24 coils.

Good luck  Flux

[Reno]

Hello windstuff a lot of what you wrote is what I was thinking when I came to this design. Do you have any opinion on the 3 individual layers for the rotors. Would this diminish the output of the center layer to a great degree. I am considering this method only for ease of construction and also was thinking of doing some phase offset with the individual layers. I am thinking somewhere around 2.5 volts open circuit per coil the speed I have yet to consifer but it will probably fall in the 300 rpm area.

I was even knocking around the idea of having the outer stator disks capable of a quarter rotation with a stop and weighted at the 10 oclock position while in operation so starting would be quicker. the outer stators would rotate with the rotor and then the stators would reach the stops and the rotor would release. When the wind was not blowing the small wieghts sitting at ten oclock would slowly turn the outer stators and rotors to 6 oclock position waiting for the next wind. Of course the magnetic forces might be to much to over come with the weight but it would be neat to try.

let me know if you have any opinions on these.

[Reno]

Hello Flux I am not sure what you mean by 'you will have to increase the coil leg length to get them to overlap.' Reading what you and others have posted I am going to wind a coil to gt an idea of how large it will end up. I will probablt allow the first few turns to fall over the top corners of the magnets and yes the coils will be in the shape of the magnets as close as possible.

[windstuffnow]

  Reno,

    With a "cut in" speed of around 300 rpm you'll need about 10-11 turns per coil going with the 24 coil arrangement to get 14 volts.(the end result wired in star ).  It depends on the size of wire your using as to the end thickness of the 3 stacked stators.  I wouldn't go any more than 3/4" thick including the clearance from magnet to stator.  It would be far more effective to overlap the coils and end up with a single layer as Flux pointed out.  You could make a plywood former to wind the coils in cutting 24 slots in it and winding them into the slots.  Remember, just like a single phase unit you will wind one coil clockwise then the next counter clockwise.

    I'm not sure I understand your weighted idea... If its cogging your worried about, there isn't a problem with start up in hugh's dual rotor design.  There is only bearing resistance  on the prop until it hits a voltage higher than the batteries.

Have Fun

Windstuff Ed

[windstuffnow]

  The microwave generator project was done similar to what your talking about... 8 pole/ 24 coils...

http://www.windstuffnow.com/main/microwave_wind_generator.htm

Instead of a steel stator, a wooden or plastic slotted jig could be made up for winding the coils then the entire jig set in the mold and filled with resin to complete the stator.

That one was built using a steel slotted stator and ceramic magnets.  You can see there is actually quite a bit of wasted wire over the top and bottom of the coils.

It actually works a little better with more magnets on each disc, you can reduce the waste considerably as well as reduce the number of turns per coil.

Have Fun

Windstuff Ed

[Flux]

 I was also wondering if the rotating discs were to aid start up,if so they are not necessary.

If the idea is to bring two phases in line at start up and change the 1.73 of the 3 phase star to 2 to increase volts it's a novel idea but completely impractical. It would be an engineering nightmare and would increase the thickness of the stator even more.

The aim is to avoid all wasted space in the stator at the point where it is between the magnets.  Three separate stator discs is not a good idea and for any form of rotation there would have to be clearance between them. They would probably shake to bits in a few minutes.

Flux

[pietko]

Nice idea...

I would like to build something similar for electric transmission for tricycle... There will be need for ~200W energy output from generator by 100RPM . Any idea what size and number of magnets per rotor and how much turns of wire will be necessary? I would say it will be better to go to the 48V output which is by 200W equal to 4.2A...

Have a nice day

Pietko

[Ungrounded Lightning Rod]

The coils should be wider.  The distance between the radial runs of the coil should be equal to the distance between the leading edges of two consecutive magnets, less the width of the radial run.  That way both magnets are driving the coil at the same time.

Usually what is done is to have a smaller gap between the consecutive magnets and make the width of the radial section of the coil about the same as the gap.  In that case the gap in the middle of the coil is about the same size as the magnet.  Since you have the gap quite wide, you need to include some of the gap on the INSIDE of the coil in order to get the right behavior.

You don't want to move the magnets inward to narrow the gap.  That would reduce their velocity past the coils, cutting the induced voltage.  If you can't afford a few more magnets, you might consider having more than three phases.  If you're charging batteries through a rectifier you want to have the wires from at least two of your phases between the magnets at all times.

You'll want to bend the inner and outer parts of the coils towards and/or away from the rotor, so the runs between the magnets will be flat and the two rotors can be closer together.  Smaller gap means stronger field, which means more voltage, which means more power.