Re: Magnetic *** Metal Fanner

Bill Miller wrote:
"Don Kelly" <dhky@xxxxxxxxxxxx> wrote in message news:lGZwl.42669$3S3.38945@xxxxxxxxxxxxxxx
Vince Morgan wrote:
"Don Kelly" <dhky@xxxxxxxxxxxx> wrote in message
news:BEFvl.24831$5t4.5548@xxxxxxxxxxxxxxx

<snip>
No need for apologies. You are thinking and that is what is important.
In theory, any magnetic field anywhere will affect another magnetic field somewhere. In practice, particularly where unsaturated magnetic material is used to direct the flux, there may be a negligable coupling between the fluxes. If the field due to one magnetic source doesn't interact or distort the field due to the other source, there is no way that the second source/ field can "see" the other source/field. *The idea in any motor is to maximize this interaction.*

* Emphasis* mine.

Don, you were doing great until the last line. (Unless I misunderstood you.)

If, in a motor, we maximize this interaction, then we run the risk of the motor locking up. IOW we run the risk of the rotor not having sufficient inertia to get past the attractive field of a stator.

It seems to me that what we would really like to do is to to maximize the interaction between the rotor and stator as the rotor pole approaches the stator and then eliminate that interaction as the rotor moves past. (or ideally to have the interaction change polarity such that the rotor is repelled by the stator.)

Bill Miller
--
Don Kelly
dhky@xxxxxxxxxxxx
remove X to reply


I see what you are getting at and admit that I have not explained this clearly. if you consider a rotor and a stator field, the torque (not the force) produced when the fields are aligned is 0, any movement away from alignment produces a torque trying to cause alignment. This torque is a maximum when the fields are in quadrature. In a DC machine, the commutator action (ideally) is such that the stator and rotor fluxes are perpendicular (both perpendicular to the common axis of rotation)- that is switching is taking place. In a synchronous motor, the fields will be rotating and preferably being at some angle in the 0 to 20 degree range (at 90 degrees- there is a maximum torque but a stability problem which is to be avoided). No switching involved In an induction motor, there is also a phase angle between stator and rotating field with no switching.
In all, when the fields are aligned, there is no torque.

As to the proposed device, the field alignment, or lack thereof is not in the direction of rotation and any forces that may occur, if they interact, will be to try to twist the rotor out of the bearings- not a good idea. The fields of both rotor and stator are ideally both perpendicular to the direction of rotation.



--
Don Kelly
dhky@xxxxxxxxxxxx
remove X to reply
.

Loading