Epoxy stator for conversions

[vawtman]

If a mold was made out of the factory laminations could the slight initial cogging be eliminated.

 Has this been tried before?

 Zubbly feel free to fly in here.

[willib]

 you want to make a mold , using epoxy, of the stator in a motor conversion

i'm not sure if that would work  , because its the laminations that transfer the flux through the windings .

[vawtman]

Your probably right That they do that used has intended.But could the mags on the rotor force things?Dont know for sure either.You are probably right and thats what im missing.Thanks

[kitno455]

there are two sets of laminations in an induction motor, rotor and stator. i assume you are talking about removing the stator lams, and building some non-metallic stator? then there would be no metal to complete the magnetic circuit from one mag to the next. that is the whole point of the lams. well, the outer case of the motor might be iron, but its darn far away from the mags on the rotor.

lots of folks build the dual rotor axial flux machine for this reason- the other mag rotor acts kindof like the stator lams in a radial flux machine.

allan

[Devo]

I would think you will still get some power as magnets would still be passing the coils but the power output would be considerably less & the effort to make the mould & fasten it in the motor housing may be quite a bit of work when skewing the magnets reduces cogging & keeps the output higher.

I guess you could do it to see what kind of power drop there is , put the rotor in with the steel laminates test it then make your new stator & compare the output.

Devo

[Ungrounded Lightning Rod]

You can fill the area within the coils with laminations - edge on to the field and to the motion of the rotor.  This will reduce the gap, letting you use much thinner magnets or increasing the voltage with a given set.  If you align the laminations as described they will have only minor eddy current losses.

The problem is that you have to get the layout of the laminations right with respect to equalizing the flux stretching as one set of magnet poles leave their laminated areas and contraction as another set approach theirs.  Otherwise you'll get KING HELL cogging - which may keep your mill from starting in winds short of hurricane force.

IT's 'way easier just to buy thicker magnets and sidestep the design and construction issues of getting the laminated cores just right.

[Ungrounded Lightning Rod]

... edge on to the field and to the motion of the rotor.

Meaning the rotating poles, if they touched the laminates, would "go sliding down the razor blade of life" rather than strumming a series of edges like guitar strings or sliding across a laminate face like a sled on a snowfall (in order of progressively higher losses).

[vawtman]

Allan your your right that the frame would be too far away.(didnt think of that)

  But what if you put the mags on the rotor without turning it?I guess it was one of those things I needed to clear.Thanks

I often wondered if the factory stator lams where the best for these.If Zubbly hasnt tinkered with these other than skewing them.Its probably not a good idea.

[Flux]

 What you are proposing is the radial equivalent of a single rotor with no path for return flux. It will work but the output will be very low compared with a normal motor conversion.

There is an additional snag that you have a solid steel or die cast aluminium frame near enough to have eddy currents induced in it.

Although possible I don't see it as practical but you will eliminate cogging.

Flux

[vawtman]

Hi Flux

What if the motor housing was thick castiron?

I know the stock rotor isnt the best and just thought the stock stator could be redone to make things more efficient has a alternator maybe not.

By not turning the rotor the coils could be mounted closer to the frame.Would that help?

Is there something that could be added to the resin to guide the flux?

In other words lets say for a class project you had to design a stator for these.Would you do it or skip out of the class thinking the teacher was nuts?

When you say less output.How much less?Sorry for so many ?s

  Thanks

[Flux]

No.  Cast iron will be as bad or nearly so. Any fixed iron near the rotating magnetic field must be laminated.

The only real virtue of a motor conversion is to use the laminated core. If you want to do it with no core, don't use this method. If you did as you proposed and managed to keep the flux away from the solid frame you may be looking at 10% of the output of the value with the stator.

If you can't solve the eddy loss in the frame it will be much worse than this.

For some reason I seem to think you are bothered with cogging. When you put it into context it is not the issue that it is made out to be.

If you do a motor conversion and make absolutely no attempt to prevent cogging then sure enough it will be very bad indeed. If you use one of the many tricks of skewing the magnets or core or asymmetric magnet spacing, then the cogging will be reduced to the point where it will not be the determining factor as far as start up goes.

Once the cogging is reduced to a modest level then the thing that will prevent start up with this type of core is the iron loss.

I know absolutely nothing about VAWTs but if start up is an issue then the best solution is to use an iron free stator and the most practical way to do that is with a dual rotor axial. The equivalent is possible as a radial but it will need a start from scratch approach rather than trying to adapt a motor. The solid metal body has to be isolated completely from the changing flux.

[vawtman]

Thanks for replying Flux.Very valuable lesson learned.My 5hp just has a slight cog in the early going.But smoothes out nicely.

 As you can tell im still in the early stages of this lovely disease.Gettin there thanks to guys like you.

My problem is that I always think theres alternatives.