material for rotor (axial flux)

pozz

Which is better steel or iron?

ChrisOlson

Re: material for rotor (axial flux)

Low carbon steel. Iron has too much nickel in it to make good generator rotors. Iron will work but the idea is to complete the magnetic circuit from pole to pole on the rotor, so low carbon steel is the best. With 1/2" thick neo magnets you'll want to use minimum 1/4" steel. With 3/4" neos use 3/8" steel to prevent saturation of the rotor. With all the magnets installed on the rotor a paperclip should not hang on the back side of the rotor. If it does the rotor is saturated and you got too much flux leakage thru the rotor.

It is normal to get a paperclip to stick on the backside perimeter of an uncaged rotor due to flux leakage around the perimeter. However, when the generator is assembled, this perimeter leakage should be close to zero and the paperclip should not stick there.
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Chris

pozz

Re: material for rotor (axial flux)

Thanks!

I would leave out the final connection of the wires from the resin to see the difference between star/delta configuration
Is it a good idea or I'll have too many losses?

ChrisOlson

Re: material for rotor (axial flux)

I never wind a stator and leave the phase ends inside. The delta configuration will give you roughly 1/3 of the internal resistance as wye, and only produce single phase voltage. The wye configuration is 3x the internal resistance of delta and produces 1.732x single phase voltage.

So, basically, the stator is wound for one or the other for a particular set of blades because the difference in rpm for the same voltage is pretty drastic.
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Chris

pozz

Re: material for rotor (axial flux)

I wanted to leave out all the endings of all the coils and connect them after

leaving space between the coils, will create vibration?

ChrisOlson

Re: material for rotor (axial flux)

You can certainly leave all the coil start and end leads outside and connect them later. That's probably best if it's your first stator since if you get a coil reversed by accident you can fix it.

Any winding will have harmonics in it at certain speeds with a certain number of poles. It's no big deal, really. The flat 4:3 pole/coil ratio axials are very forgiving in that respect so the space between coils will be a non-issue.
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Chris

pozz

Re: material for rotor (axial flux)

Thanks for the advice