Alan B
100 GW
Let's keep it technical, folks.
Alan B said:Let's keep it technical, folks.
Buk___ said:...
The motors we use have much more complex topology, and far more complex and contained magnetic circuits. Something like this (simulated on a similar 100mm diameter scale to the wire loop motor simulation above):
4pole3toothMotorMagbeticCircuits.jpg
??Buk___ said:Sorry, but that contradicts everything I've read.major said:No motion of magnet or coil. And can be very strong. Often is the maximum torque for a motor.
major said:Buk___ said:...
The motors we use have much more complex topology, and far more complex and contained magnetic circuits. Something like this (simulated on a similar 100mm diameter scale to the wire loop motor simulation above):
4pole3toothMotorMagbeticCircuits.jpg
4pole3toothMotorMagbeticCircuits.jpg
Perhaps you can elaborate on this simulation of a motor, as you say, having "much more complex topology, and far more complex and contained magnetic circuit". For instance, is it a 3 phase BLDC? Also, do the lines represent flux from 4 magnets? Is this design and simulation your handiwork or from elsewhere? Does a real model (hardware) exist? Why did you decide to post it in a reply to my post concerning end-turns and effective armature conductor length? Thanks in advance.
major
magnetic B-field lines neither start nor end (mathematically, B is a solenoidal vector field); a field line either extends to infinity or wraps around to form a closed curve
billvon said:The interaction of these two fields produces torque in a motor, whether it is stationary or spinning.
JanComputerman said:It may help in the above diagram 3 pole rotor with 4 pole stator to indicate N S poles of all parts
JanComputerman said:I know I get confused when the stator and rotor have different numbers of poles which I assume is done to reduce cogging
JanComputerman said:but adds to the complexity of the calculation for torque since how much each pole contributes is not equal and becomes a function of their angle of rotation relative to the stator poles they are interacting with. Geezzz I am aquiring a deeper understanding of this than I ever expected. My brain is starting to get full!
JanComputerman said:From a programming perspective I can give you this one piece of advice, make sure you have the sign (+/-) correct when adding up totals taking into account which side of the rotation axis you are on and what side of the core tooth you are on.
Sometimes the old textbooks were just wrong ...too!
Buk___ said:I also do not take things as read without questioning stuff, until my own understanding gells with received wisdom, or surpasses it.
I certainly don't hang on the coat tails of others -- John was right, Miles was right, Major was right -- especially when in two out of 3 of those cases, they weren't.
Nor do I follow people around from thread to thread, posting non-contributory "how dumb are you that you had to ask that question"; and when challenged, construct a character assassination piece in a fit of pique.
Buk___ said:I will continue to model, and research and if I find the means and resources, physically test until I find definitive evidence; for or against.
I will (Gatekeeper permitting) continue to discuss and debate anyone who feels inclined to reason with me (for which you and AlanB have my profound thanks).
Buk___ said:... Lenz Law require the magnets to be moving; ...
Punx0r said:Calm down, dear. ....
Then I would suggest you ...
major said:Buk___ said:... Lenz Law require the magnets to be moving; ...
I don't think so. The law addresses a changing current in a conductor or coil. When viewing web explanations or textbooks, often an illustrated example is seen using a moving magnet, but the law does not require a moving magnet.
major
Sort of. All the Lenz law says is that any current you induce due to a changing magnetic field will always oppose the field. In this case that means that if you short the windings of a motor, it will be very hard to turn - because the current you induce in the coils will always oppose the magnetic field as it changes. That's true whether or not you already have a current flowing in that coil, due to superposition.Buk___ said:Major suggested that Lenz Law might be a way for the physical Lorentz force acting on a conductor in the static stator, to feedback and apply torque to the remote rotor.
billvon said:So the Lenz law will indeed contribute to torque of a stalled motor,
Buk___ said:billvon said:So the Lenz law will indeed contribute to torque of a stalled motor,
But ... Lenz Law induced current and the field it creates, opposes the current that originated it and the field it creates, so rather than "contribute to the torque of the stalled motor", it would have to detract from it.
It could only contribute to it, if it was the primary source of the motive power in the direction of motion and overrode that opposite torque created by the phase current; but for it to do that would require the inverted amplification of the phase current, and that violates the conservation of energy, by creating some.
major said:Buk___ said:billvon said:So the Lenz law will indeed contribute to torque of a stalled motor,
But ... Lenz Law induced current and the field it creates, opposes the current that originated it and the field it creates, so rather than "contribute to the torque of the stalled motor", it would have to detract from it.
It could only contribute to it, if it was the primary source of the motive power in the direction of motion and overrode that opposite torque created by the phase current; but for it to do that would require the inverted amplification of the phase current, and that violates the conservation of energy, by creating some.
Bill's shorted motor turning exercise actually runs the machine as a generator. Understand difference between generator and motor.
he had to be talking about when it was being run as a motor; because generators don't generate torque for Lenz to contribute to. Right??So the Lenz law will indeed contribute to torque of a stalled motor,
major said:Because you watch a video which explains the motor operation by simple magnetic attraction and repulsion doesn't refute the basic principles and laws, to some of which I have referred. Those still apply, as always. And they are not small or whimpy as to be ignored.
The sense was to demonstrate the 1/R^3 fall of Lorentz force with distance.major said:Yes you can do math and simulation. But what sense is there to find force on each of 20 or 30 conductors in air between bar magnets?
major said:That is never the case in a motor with a core and supporting magnetic structure.
major said:... so you claim them wrong ...
major said:the fallacy of your proposition that end turns contribute magnetically to torque production.
Alan B said:anything wrapped around a tooth is part of a turn and contributes flux to the tooth (or anything contributing to the flux of the tooth is a good turn).
Alan B said:If I look back at post #1 of his thread, I think the problem is the precise definition of end turns.
As I see it (and I'm not a magnetics expert, though I did have the pleasure of working with some), anything wrapped around a tooth is part of a turn and contributes flux to the tooth (or anything contributing to the flux of the tooth is a good turn).
Alan B said:Anything that departs from the tooth and heads off somewhere else is not part of a flux contributing turn. So perhaps that is the definition of an "end turn". It goes to the next tooth that needs to have that same current, and the flux it creates on the way is not directed in an efficient and useful manner. So this is wasted flux, and wasted I squared R loss. It might have some small effect in either a positive or negative direction, but it does not have the precise focussed permeability magnified effect of the coils around the tooth.
Alan B said:The trick here is that all the fundamental principles are simultaneously at play, but the magnitudes are important and unequal, and the time domains affect the combinations as well. Some things are operating on the microseconds scale while others are in the many milliseconds. The motor's operation sums all of this. The experts are rarely wrong, but understanding them is not easy. The textbooks are infrequently wrong as well, but are often guilty of simplifying things, ignoring effects that are small but will be important in some cases, especially when applying those theories to other situations. That is the material of further study or graduate work, where you find out that what you learned earlier was approximately right.
major said:Another clue is Ampere's Law. The contributing current to the magnetic flux in a core is that which passes through the core. Current passing around the outside of the core does not contribute magnetically but only serves to deliver current to the active portion.
I think that might be a pretty fundamental point.Buk___ said:Understood (without you telling me), but when he said:he had to be talking about when it was being run as a motor; because generators don't generate torque for Lenz to contribute to. Right?So the Lenz law will indeed contribute to torque of a stalled motor,
billvon said:generator torque
John in CR said:To the extend end turn copper is longer than the minimum necessary it is added resistance with no extra torque produced from the same current. That's the "bad" part.