Magnetic Theory
Magnetic Theory
(OP)
I have a question regarding magnetics which I can't find a definite answer for, hoped someone could help. The question is "If a static hoop of iron, eg. a horseshoe, is set near a rotating cylindrical permanent magnet which has north pole at one end and south at the other so that one end of the hoop approaches the north pole and one end approaches the south pole, is a torque imparted to the hoop? How much?"
N -]=[- S
U
The core issue is, does this setup cause the breaking of magnetic lines of force in a manner similar to eg. a claw-pole synchronous generator where the hoop is rotated 90 degrees and the magnetic shaft has alternate projections inward from each pole? BTW, I have little access to handbooks or texts, appreciate web ref's etc.
Thanks for your help
N -]=[- S
U
The core issue is, does this setup cause the breaking of magnetic lines of force in a manner similar to eg. a claw-pole synchronous generator where the hoop is rotated 90 degrees and the magnetic shaft has alternate projections inward from each pole? BTW, I have little access to handbooks or texts, appreciate web ref's etc.
Thanks for your help
Pechez les vaches.





RE: Magnetic Theory
If A - rotating about it's axis so that the north and south pole stay in the same position, then that magnet generates a constant magnetic field and will not induce current in any loop.
If B - rotating so that N and S end swap - then it is capable of inducing a current. But your U-piece of iron does not constitute a loop so no current flows.
I both cases A and B there is no current flowing. Without current flowing there is no torque.
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RE: Magnetic Theory
It covers three new configurations of synchronous electric motors, the second of which exploits the above configuration to excite the rotor pole pieces. eg see {images}, {drawings}, {Fig 5}. The exciter magnet is the stationary drum at the centre 14 with ring extensions 16 up each side of the stator to connect magnetically with the rotating pole pieces 6. Basically a "claw pole synchronous" machine with the "claws" separated from the exciter. Presuming eddy currents are defeated, how much power will be lost in transfering the magnetic field from the fixed exciter to the rotating pole pieces?
I take your response to be "none / negligable".
lengould (@) ecologen.com
Pechez les vaches.
RE: Magnetic Theory
Pechez les vaches.
RE: Magnetic Theory
"Presuming eddy currents are defeated, how much power will be lost in transfering the magnetic field from the fixed exciter to the rotating pole pieces?"
That sounds reasonable to me. The only ways I can think of for a magnetic field to dissipate real power are:
1 - to create eddy currents as you mentioned you have discounted.
2 - to interact with an induced current in a loop such as the rotor of squirrel cage motor... I don't think you have a loop although I haven't looked loop?
3 - to interact with a forced current from some other source... I don't think you have any sources other than the field and the armature.
4 - hysteresis losses - most severe for high-frequency fields and ferrous material.
There is a separate question of reactive power... leakage impedacnes etc. Not related to real power.
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