A donut electromagnetic core comprises main section + movable section

[artis]

From reply #13, then after, I assume the cylinder is replaced with an infinite area plate with thickness equal to original height of the solid cylinder, and no more rotation, but linear motion.

My only concern is whether the motion of wire (combined with plate), is affected by the plate in term of induction effect.

By my imagination, the contact area between wire and plate seems not to cut B flux, as the motion may stickily drag the MMF lines if not instant straightening (reconnect to nearest magnetic domains); only the wire upper portion causes flux change?

Following sketch illustrates the combined wire and plate moving towards reader.

If the plate is attached with the C core, and let the wire independently move, is there the same induction effect? View attachment 321629

I think I know what your trying to do. Creating a motor where the rotor is a single magnetic pole with field lines extending outwards or inwards along the whole rotor surface and the stator being the opposite magnetic pole , then you can put a wire in the airgap between the stator and rotor or attach it to rotor surface , pass current through that wire and it will continually be pushed around as it cuts the never ending single direction flux between the stator /rotor.I can say immediately that the first problem is that the magnetic loop has to be long , the longer a magnetic loop is the more lossy it becomes so you will need more energy to create the same strength field, or more permanent magnets, second problem is unless you wish to put slip ring on the periphery of the rotor where there is high angular speed you will have to use the rotor axis as a magnetic field return path, rotor axis are usually made from hardened ferrous steel which is not nearly as great in terms of magnetic permeability as soft magnetic steel used in laminations for transformer cores and electric motors.In theory it works, in practice it's worse in power to size/volume ratio, it's more complicated and it doesn't surpass existing motors/generators in the parameters.
Sorry to say but this is not a new idea , it's just not practically efficient or better therefore it's not used.

One additional note is that such a motor would have only a single turn in the rotor, so a very low resistance path which would be impractical for almost all applications and energy sources.
For more than single turn in the rotor you would need additional slip rings, so 1 turn needs 2 slip rings , 10 turns would require 20!!! slip rings one for each turn start and end.

It's essentially a faraday disc just with different geometry.
Did I got your idea? Is this a good answer ?

 

[cairoliu]

I think I know what your trying to do. Creating a motor where the rotor is a single magnetic pole with field lines extending outwards or inwards along the whole rotor surface and the stator being the opposite magnetic pole , then you can put a wire in the airgap between the stator and rotor or attach it to rotor surface , pass current through that wire and it will continually be pushed around as it cuts the never ending single direction flux between the stator /rotor.I can say immediately that the first problem is that the magnetic loop has to be long , the longer a magnetic loop is the more lossy it becomes so you will need more energy to create the same strength field, or more permanent magnets, second problem is unless you wish to put slip ring on the periphery of the rotor where there is high angular speed you will have to use the rotor axis as a magnetic field return path, rotor axis are usually made from hardened ferrous steel which is not nearly as great in terms of magnetic permeability as soft magnetic steel used in laminations for transformer cores and electric motors.In theory it works, in practice it's worse in power to size/volume ratio, it's more complicated and it doesn't surpass existing motors/generators in the parameters.
Sorry to say but this is not a new idea , it's just not practically efficient or better therefore it's not used.

One additional note is that such a motor would have only a single turn in the rotor, so a very low resistance path which would be impractical for almost all applications and energy sources.
For more than single turn in the rotor you would need additional slip rings, so 1 turn needs 2 slip rings , 10 turns would require 20!!! slip rings one for each turn start and end.

It's essentially a faraday disc just with different geometry.
Did I got your idea? Is this a good answer ?

You really catch my idea.
But how do you think one turn need one pair of slip rings? If you are right, my idea will become junk.
I thick multiple turns can use one pair of slip rings.

 

[cairoliu]

It's essentially a faraday disc just with different geometry.

Yes, mine looks like Faraday disc, but I don't use the disc-itself as conductor, but use multiple turns copper wire coil pasted on surface of disc. So the disc should be an good soft magnetic steel which is almost non-conductor.

Generally speaking, if a material is a good electric conductor, it must be a bad magnetic conductor, so the Faraday electric disc is very different with my magnetic disc.

The induction force firstly drive the copper wire, then the disc is passively driven by glue that hold wire & disc together.

 

[artis]

You really catch my idea.
But how do you think one turn need one pair of slip rings? If you are right, my idea will become junk.
I thick multiple turns can use one pair of slip rings.

Think about it, it's simple, if your rotor to stator flux is all in one direction all around the rotor surface then you can't pass wire back and forth, you can only pass wire in one direction and current also in one direction.
If you put two wires next to each other and pass current in opposite direction then one wire will try to turn left while the other right, you will have a perfectly canceling torque and no movement.

Therefore for a design like this you can only pass current in one direction and then use a return path for the current that is OUTSIDE!!! of the flux that you are working with.

So yes you need two slip rings for each loop/turn of such a motor.

It does work in theory and would also work in practice it's just extremely inefficient to do a motor this way.

It has too long magnetic field path and needs a lot of slip rings , or the other way is to do it like the faraday disc is done instead of many turns, have just a single turn but then you need huge amperage to get any real torque.
I'm talking kilo amps!

Sorry buddy, but this idea doesn't fly.