quote:

Posted by Motor Doc:I look forward to seeing Jan's results. I will comment on the experiment design after I get to watch.

Somehow you must have overlooked the results. I will just repeat it for you: The iron developed 239 grams of force, the cage developed 4.3 grams of force. You can watch it on one of the 3 pictures attached to the first post including the current and the voltage. What are your measurements? (Or is it a secret again?) Your experiment confirmed without any reasonable doubt, that when you shove a two-by four into a motor, it does not spin.

quote:

You are right, we have already completed measurements and have continued on with the study. Very interesting and we were very right.

I bet you were right on something. But not on the ratio of the force on the iron and force on the bars. I came up with ratio 1: 50 (cage to iron). You came up with what? Give me a number, please? Somehow it is missing in your post.

quote:

I do find it also interesting that years after the development of the contraption and months after the posting of the video that Jan has developed this experiment.

The “contraption” is just a cute name for an induction motor. I am no aware that your name would be attached to the invention of it. In fact, the “contraption” is a very unnecessary exercise. The F=B.I.L says everything. I had to do a similar experiment to expose the misleading conclusions of the Dreisilker video.

The rest of your post is reminiscent of the stuff that we are used to hear from you: Something that is totally unrelated to the discussion.
For those interested, the sketch of the cross section of my experimental induction motor is attached.
jank

cross_section.doc (104 KB, 14 downloads)

[QUOTE]Originally posted by David_G:

I would've defined this Law as follows:
When two magnetic fields are superimposed, thus distorting the symmetry of the original individual magnetic fluxes density in the area, the force applied to the respective source will be directed, if no restriction exists, to cause the source move in a direction eliminating the above distortion.
QUOTE]

You are too preoccupied with the distortion of the original field by the presence of the conductor carrying the current. The genius of the founding fathers of the electromagnetic theory (including Maxwell and the Lorentz) is mostly in the fact, that they made the calculations of the forces possible. In your definition, there is absolutely no way to know, what the flux density is in the vicinity of the conductor placed in the external magnetic field. The shape of the field is so incredibly complicated!
But that is not what the theory says. If you want to find the force on the wire with current, you first look at the field itself. Forget that the current exists, turn the current off. Secondly, look at the current that flows through the wire, forgetting what the external field looks like. As before, you can as well turn it off (the external field). Now you have 2 numbers, B and I. Just add the length of the wire, and you can calculate the force! This discovery is absolutely stunning and beautiful, in my opinion.
Let’s add it to our knowledge much more than 100 years after it came into being!
jank

David – I roughly agree with your comments in general as an attempt to provide a qualitative discussion. I would add that Lorentz law works fine exactly as-is for predicting force on current carrying conductors and was used for that purpose in the derivation of the 4-step proof. I have provided qualitative discussion of the broader context of predicting magnetic force in section 6 of the Long Version. I have provided quantitative discussion of the same subject in section 7 of the Long Version (energy method for computing force when iron is present).

quote:

motordoc
Also, thank you for linking the video. I have no problem with that. And summarizing the statements, more or less accurately.

Thanks for entering the discussion and making your position clear. I will take that as an acknowledgement that you are sticking to your 3-year-old claim that the normal torque producing in a standard induction motor (conductors in slots) acts primarily on the conductors rather than on the core (iron).

The tone of your discussion seems quite distorted in relation to proof on either side of this argument. For starters, there is this:

quote:

motordoc
I do find it interesting that even with obvious results there is some excuse why it did not demonstrate anything.

It should be revealing to forum members that the results you claim are shown on the video (force acts on conductor not core) are supposedly so "obvious" that my objections (08 October 2009 09:59 PM) to your video should be labeled as an "excuse". Apparently we are supposed to believe the result is so obvious and the objections so frivolous as to not even warrant any specific response to my specific comments?.....

Everyone can see the video....this should be something other forum members can judge for themselves..... does Howard's video really show "obvious" results that he claims? Should my objections (08 October 2009 09:59 PM) be dismissed as excuse without any discussion? From where I sit, Howard's view on this matter seems more than a little bit skewed.

quote:

I look forward to seeing Jan's results. I will comment on the experiment design after I get to watch.

Jan has already posted detailed description, photo, quantitative results, and offerred openly to address any questions. Doesn't that constitute results?

I would certainly like to hear a similar full discussion of Howard's test results – for starters a general description of the machine, voltage applied, frequency if differing from 60hz, and numerical values of forces measured on the core and on the conductor.

Also it is interesting that Howard seems to have ignored the detailed proof based on first principles which has long ago been posted in the "short version", supported by the "long version here:"
http://home.comcast.net/~electricpete1/torque_web/
There is the 4 part proof – broken into parts #1, #2, #3, #4 in order to narrow down the area of disagreement. Each of the first three parts stands independently as a conclusion supported by the long version. The fourth part is logical combination of the previous three to support the force-on-core conclusion. If you claim to believe the force acts primarily on the core, then surely you can articulate some error that you think exists in the 4 part proof.... which part is in error: #1, #2, #3 or #4?

quote:

motordoc
You are right, we have already completed measurements and have continued on with the study. Very interesting and we were very right.....
The results of all work are being published and posted as we determine they can be released and following patent application. Whether or not I do so here is at my own discretion.

To me, that is a claim of a proof without providing any proof.... and an empty promise of proof to be provided in the future with no timetable. As reminder, we first heard Howard say on 29 October 2006 06:41 PM "I am going to put this together as a paper referreed by my peers."

We didn't get any peer reviewed paper, but we did get a whitepaper posted. Let's have a look:
http://home.comcast.net/~elect...53882_rotor_bars.pdf
Some flaws that are readily apparent:
1 - Figures 1 thru 4 are the centerpiece of Howard's theory of how a motor works. None of them have conductors located in slots. The conclusions drawn for these simple devices in figures 1 thru 4 do not reflect the reality of an induction motor with conductors in slots.
2 – In the conclusion section on page 12 it is stated "In order for the forces to work directly in the rotor teeth, the rotor core teeth would have to be solid, not laminated." This is completely incorrect – the mechanism for force on the iron was shown in the long version and has everything to do with the permeability of the iron - nothing to do wtih any circulating currents in the iron. One can also verify by holding a magnet next to a piece of iron (both stationary)... there is no current but there is magnetic force on the iron.

For further discussion of points 1 and 2 above, see Section II (Slots Make a Difference) and JJ (Laminations) of the rebuttal posted here:
http://home.comcast.net/~elect...eb/RebuttalMrXR1.pdf

And now 3 years later, all we have from Howard on this subject is a flawed whitepaper, an ambiguous video without any attempt to address very specific objections raised above, no coherent theory to explain how the majority of the force supposedly acts on the conductor when the conductor is shielded from flux by the iron, no peer reviewed paper, and now repeated claims of some proof yet to be shown in the future. I for one don't give much weight to claims such as this.

quote:

You are too preoccupied with the distortion of the original field by the presence of the conductor carrying the current. The genius of the founding fathers of the electromagnetic theory (including Maxwell and the Lorentz) is mostly in the fact, that they made the calculations of the forces possible. In your definition, there is absolutely no way to know, what the flux density is in the vicinity of the conductor placed in the external magnetic field. The shape of the field is so incredibly complicated!

But that is not what the theory says. If you want to find the force on the wire with current, you first look at the field itself. Forget that the current exists, turn the current off. Secondly, look at the current that flows through the wire, forgetting what the external field looks like. As before, you can as well turn it off (the external field). Now you have 2 numbers, B and I. Just add the length of the wire, and you can calculate the force! This discovery is absolutely stunning and beautiful, in my opinion.

On this rare occasion, I will offer a slightly differing opinion than Jan. The standard finite element solution (for example per Bastos and Sadowski) does in fact require solving the total flux density B from all sources (including distortion from any current), and then finding the force on non-magnetic current-carrying conductors as F = Integral I x B dL = Integral J x B dVolume. (using total B).

However the difference in approaches is not great. If we make the simplifying assumption of a linear system (constant mu within those materials that are magnetic, rather than mu varying with flux density), then we can apply the principle of superposition which tells us that the total flux density at any location is the sum of the individual flux densities due to each “source” acting alone. For example let the current carrying conductor be called source 1 and external field is source 2. Their respetive fields are B1 and B2. The total field is Btotal = B1+B2 (under the linear assumption for iron properties). We can break the force into two components as follows: Ftot = L I x Btot = L I x B1 + L I x B2 = F1 + F2 where F1 =L I x B1 and F2 = L I x B2.

The force Jan has proposed is LI x B2. We can see this will match the above Ftot if and only if F1 = L I x B1 = 0. In other words it is correct if the conductor alone (in absence of external fields) experiences no force. In most cases, this F1 term is in indeed 0, i.e. the force on the current carrying conductor due to it’s own field is usually zero, therefore the two approaches (considering only external field or considering total field including distortion from conductor itself) give the same force result (adding the zero force from the conductor doesn’t change the result). However there are scenario’s where the conductor acting alone (in absence of any external field) will cause a non-zero force on itself. One situation where this would occur would be predicting radial force on the conductor within open rectangular slot – in this case we need only current in the conductor itself to establish a downward force on the conductor. The only way to find the total force in this case would be to consider the total (distorted) field from the conductor and any external field. In the more usual case when the conductor acting alone (without other sources) does not create force on itself (such as tangential torque-producing force for conductor in centered tangentially within a slot in iron), then we need only consider the external field and do not need the complications of “distortions” produced by the current itself. In this case it allows as Jan had said a more elegant analytical approach since the external field alone generally has a simpler form than the combined / distorted field

quote:

Somehow you must have overlooked the results. I will just repeat it for you: The iron developed 239 grams of force, the cage developed 4.3 grams of force. You can watch it on one of the 3 pictures attached to the first post including the current and the voltage.

This string is about your experiment (based on your other comments). I am just waiting for the video, then will comment on the setup.

So far all I am seeing is the usually repeated stuff. I will catch up in a few weeks and see if there is any substance or anything new.

I thought this was going to be about Jan's experiments but somehow it seems to be all about me again. While I am flattered, I would rather see the video on the experiment so that we can compare notes. Constructive versus the usual stuff on this topic. Personally, I have better things to do than that.

I have my results, and they were what I expected. However, I feel that it is important in any R&D to keep an open mind, especially when I see what I expect and there are others that claim the opposite. To start posting those results now, based upon the tone I am seeing, would detract from your work.

So, I will step back, read, and hope there is something other than a couple of guys going after another individual. I can watch that on political forums.

Have fun.

Howard

Jank, EP

According to Lorentz's Law, to quantify the force it is sufficient to know B, L, and I.

However, in order to understand how this force is being derived, superposition of magnetic fields is necessary and broader approach has to be taken.

This message has been edited. Last edited by: David_G,

DavidG – I agree – there is a place for both approaches. Use of complete flux density (including distortion from the current to be studied) is suitable for computer solution and graphic representation and does provide some intuition as you say (see "long version" section 6 discussion of flux lines in air... act like stretched springs). On the other hand, as discussed above, there is a large class of problems where ignoring the effect of the conductor current upon the field results in an elegant simplification without any loss of accuracy in computing total force on the conductor. This extends the range of problems which can be solved analytically (vs numerically) and therefore can be a very powerful tool.

Howard:

quote:

motordoc wrote:
I thought this was going to be about Jan's experiments but somehow it seems to be all about me again. While I am flattered...

There is no reason you should be surprised or flattered by someone questioning your claims. Your claims contradict basic physics as shown in
the short version: http://tinyurl.com/yhp6oyu
and the long version: http://tinyurl.com/ygt6azo

The proof is there, built from the ground up (Maxwell's laws and conervation of energy), easily verifiable by anyone that has the time and background to understand it. But the invitation to discuss (which item is disputed: #1, #2, #3 or #4?) remains open and unanswered as it has for more than three years.

Multiple references specifically addressing the same question and coming to the same conclusion are discussed in Section 17 of the Long Version.

There is also the results of Jan's experiment presented in the first post of this thread. He has already responded to multiple questions quite satisfactorily. For my part, I don't see any reason to challenge an experiment which matches exactly what is predicted by Maxwell's equations. (You are of course free to ask specific questions and articulate specific objections as has been invited.)

On the other hand, we have only your video with spoken words contradicting what we see with our own eyes ("The core did not move. Nope, the core did not move."). When we analyse what we saw on the video with our own eyes, there was no proof to be found. When we express very specific objections (08 October 2009 09:59 PM), there is not a single specific response ... the objections are simply dismissed as excuses (13 October 2009 02:05 PM).

quote:

motordoc wrote:
So, I will step back, read, and hope there is something other than a couple of guys going after another individual

No-one is "going after" anyone. There is persistence in seeking resolution by identifying your obvious failure to articulate any objection to the theoretical proof and your obvious failure respond directly to my specific objections regarding your video. Most people interested in open discussion would respond to such identification by directly and specifically addressing the questions raised.

This message has been edited. Last edited by: electricpete,

Unlike Wally himself, I have been listening to him, and made a little video. I was actually very surprised how easy it was. I did not use a camcorder, but an ordinary digital camera.
What you see is a startup of my experimental induction motor. Unlike when I measured the torques, in this experiment the voltage is not increased gradually, but across the line. The current reaches about 5 Amps.
The initial position of the cage is roughly in the center of the slot. You can see it clearly observing the 12 o’clock or 1 o’clock slot or bar. The power is turned on and without any hesitation the iron takes off. The cage stays behind. Then you can hear few clicks as the bars bounce from the trailing edge of the iron slot, and the motor accelerates towards the full speed. What you cannot see is that the cage stays on the trailing edge of the rotor slot being dragged along by the iron. It would be seen with the strobe light (that I forgot at work today).
For your information, the inertia of the cage is about 50% lower than the inertia of the iron. Yes, the cage is quite heavy due to massive end rings.
By the way, thank you for your lesson Pete. It makes perfect sense, and I will return to that topic little later.
jank

I am sorry Wally gator, I confused you with the Wally that never listens to what he is saying. Thanks for the tip.

This message has been edited. Last edited by: jank,

VIDEO_OF_THE_STARTUP.avi (889 KB, 58 downloads)

Hi Howard,

Unfortunately, I joined the motor testing forum after the original thread on this subject had been deleted. However, I do have a few observations regarding the present thread.

quote:

...we have already completed measurements and have continued on with the study.

I watched the video that you cited; it gives no measurements. Nor does it clearly show what the narrator says it shows. I think it will be much easier for you to explain your conclusions if you include the results themselves. Without results, there is no science.

You also may want to re-shoot your video. Look at jank's video; it has been shot in such a way that the stated effect is obvious to anyone. That would be a good example to follow.

quote:

Very interesting and we were very right.

What were you right about?

quote:

I do find it interesting that even with obvious results there is some excuse why it did not demonstrate anything.

I'm sorry, but I have to agree with others who have noted that the video does not show obvious results. Play it for someone with the sound turned down; I think you'll see what I mean.

I'm also puzzled as to your use of the word "excuse". It seems to me that those who have raised objections to your theory have supported those objections with rigorous and thoughtful work. You have addressed almost none of it.

quote:

I do find it also interesting that years after the development of the contraption and months after the posting of the video that Jan has developed this experiment.

That is an easy one. You raised the subject a few weeks ago in an unrelated thread. One forum member invited you to move the subject to a new thread. You did not do so, and another forum member elected to conduct a similar experiment, albeit with published results.

quote:

I look forward to seeing Jan's results. I will comment on the experiment design after I get to watch.

Why would you need to see a video to comment? Maxwell didn't need a video camera to write his laws. Yet his experiments were reproducible. Why not add data so that your experiment can be reproduced by others? This is a basic tenet of scientific experimentation.

quote:

I am just waiting for the video, then will comment on the setup.

For goodness sake, you work in a motor shop - why not try to duplicate Jan's experiment? It is the next logical step, and given that someone else has contributed considerable time and effort on a subject that is obviously important to you, how could you not?

quote:

So far all I am seeing is the usually repeated stuff.

What is the usually repeated stuff?

quote:

I will catch up in a few weeks and see if there is any substance or anything new.

This comment is familiar to me.

quote:

I thought this was going to be about Jan's experiments but somehow it seems to be all about me again.

I disagree. I think it is about your theory and your experiment.

quote:

While I am flattered, I would rather see the video on the experiment so that we can compare notes.

It looks like you have a video to watch now.

quote:

However, I feel that it is important in any R&D to keep an open mind...

Actually, it more than that. It is obligatory.

I'm sorry, Howard, but the material you have shared so far has outlined a theory, but provides no data that supports that theory, nor any data that addresses issues which others have raised. Yet you state that you have proved something. Can you post some data?

With data, you can bring substance to your opinions. The ball is firmly in your court.

This message has been edited. Last edited by: Jack Rosebro,

quote:

By Electricpete:
However there are scenarios where the conductor acting alone (in absence of any external field) will cause a non-zero force on itself.

It is indeed necessary to make sure, that the conductor does not experience any force by its own field. For a rotor bar in the slot (in an ordinary motor) it is certainly the case. You can imagine that the rotor bar is a conductor between two ferromagnetic walls. The case can be solved by placing the mirror image of the conductor on the “other side” of the ferromagnetic wall exactly like an image in the mirror. The conductor filling the whole slot would have 2 identical mirror images, one on the left and one on the right. Hence one mirror image pulls to the right and one to the left and the resulting force is zero.
This is not the case of the experimental motor with bars loose in the slot (such as my experimental motor). For the measurements, I have always positioned the bars to the center of the rotor slot. You may have noticed that one of the torque bars on my experimental rig has an adjusting screw. Using the screw I could position the rotor bar in any point of the rotor slot (along the diameter circle). And the force on the bars indeed changed dramatically. When was the bar moved towards the leading wall of the rotor slot (in the direction of the rotation), the force on the cage roughly doubled. When moved to the trailing edge, the torque was close to zero or even slightly negative. The substantially higher torque of the iron did not seem to be affected.
The ratios would of course vary with different input voltages
When conducting experiments on similar setups, it is necessary to take the above facts into the consideration.
Also both cases that David_G drew on October 7, 2009 would experience forces on conductors without any external field (both to the right, no matter which direction the current flows). It would probably further complicate the analytical solution, and the finite analysis would be likely faster way to solve the problem.
jank

Great video by Jan.

FWIW - here is my attempt to analyze it and discuss what conclusions can be drawn:

We definitely see movement of the iron/core before the conductor/cage by looking at the 12:00 or 1:00 positions as Jan said. I had to repeat it a few times to see it. You can slow down your video or advance it frame by frame if that doesn’t jump out at you.

From this observation, we judge that the iron core was initially (upon starting) accelerating faster than the conductor cage. I will continue to discuss what conclusion we can draw from this starting behavior (I’m not focusing on running behavior… will get to that later).

The rotational equation for acceleration (similar to F = M * A) is
Taccel = J * dw/dt
Where:

• Taccel is accelerating torque
  
• J = rotating inertia
  
• dw/dt = rotational acceleration (rate of change of radian rotational speed)

Since the core accelerated faster than the cage:
Tcore / Jcore > Tcage / Jcage

Jan has told us that the cage inertia is about 50% of the core inertia: Jcage ~ 0.5* Jcore
Tcore > Tcage (Jcore / Jcage) ~ Tcage * 2
Tcore > 2 * Tcage

i.e. the total torque on the core is more than twice that on the cage.

Now at this point it should be remembered that the total torque includes contributions from both electromagnetic torque producing force and friction forces

The friction forces are divided in 2 types: air friction and bearing friction:

• Air friction is roughly proportional to speed^2. It could be very important when the machine is running at full speed, but is completely insignificant when the machine is just getting moving that first fraction of a turn. (at this time we have very high electromagnetic torque producing forces and lowest air friction forces… the air friction can be safely judged as negligible)
  
• Bearing friction is hard to analyze in general, but for this particular experiment we can draw an important conclusion by looking at the cross section of the motor. The cage is mounted onto the outer race of a bearing whose inner race is connected to the shaft, where shaft travels at same speed as core. Since we observe that the core is moving faster than the cage during that initial period of movement, the effect of that bearing friction during that period will actually be to accelerate the cage rather than decelerate. So friction cannot slow down the cage when the core is moving faster than the cage. The error introduced by bearing friction during this particular experiment is in the conservative/generous direction (core/shaft bearing slows down core while conductor/cage bearing speeds up cage during this interval).

Based on above we have high confidence from Jan’s video that the electromagnetic torque producing force on the iron core of his motor is at least twice that on the conductor/cage during starting.

Now a discussion of differences between starting and running:

• If voltage was reduced significantly in order to obtain a slow-enough start to see by eyeball, then it shifts the flux density in a direction that tends to favor the force on the conductor/cage (error in the conservative/generous direction) because as stated above (08 October 2009 07:14 PM ) normal operating flux density generally provides the highest permeability and highest ratio Fcore/Fconductor… anything else produces lower Fcore/Fconductor. Experiments conducted at non-operating flux density will have an error in the conservative/generous direction for those seeking to prove operating-condition Fcore>Fconductor.
  
• There can be a transient decaying dc offset current present upon initial start – this again can act to shift the flux density away from the normal operating range and again would be in the conservative direction.
  
• There is some difference between starting and running in terms of current distribution within the bar. It is a small effect with Jan’s small conductor cage, but perhaps still present. During starting, due to the high frequency seen by the rotor, the current tends to crowd the “top” of the bar (toward the airgap) where the least cross-slot flux is linked (“deep bar effect”). But the top of the conductor is precisely where the radial flux is highest (see long version figure 6a or 6e…take your pick). The result is that during starting the current distribution is more favorable to conductor torque production than during running. This is once again an error in the conservative/generous direction if we are using an experiment under starting conditions to prove the core force under running conditions is higher than the conductor force.

So my overall conclusion about the video: the initial response shows higher torque-producing electromagnetic force on the iron/core than conductor/cage during starting conditions and we therefore expect higher force on the core to continue during normal running conditions. I don’t see any errors or effects in the non-conservative direction that would modify the above conclusion. I am open to comments if anyone sees it differently.

I did not focus too much on the full-speed no-load running condition. When at full speed/no-load, the air friction will be much higher and the electromagnetic torques much lower than they were during starting. Since the air friction is somewhat of an unknown to me, it seems more of a challenge to interpret results of a test at full-speed no-load operation than it was to interpret the starting results.

I will also continue to remind folks of the single most important fact in this entire thread: we already have a proof (that the normal torque-producing force in a standard induction motor acts primarily on the core rather than conductors) based on indisputable principles of physics (Maxwell’s laws and conservation of energy) !

This message has been edited. Last edited by: electricpete,

The proof (#1, #2, #3, #4) of my position and Jan's position based directly upon indisuptable laws of physics was given over 3 years ago, but for some reason it remains completely ignored:
the short version: http://tinyurl.com/yhp6oyu
and the long version: http://tinyurl.com/ygt6azo

I suspect the reason for ignoring the proof is that it is not easily understandable for people that don't have an education in calculus-based electromagnetics. (that is not a knock on anyone's intelligence or competence, but the plain reality is that some things cannot be readily understood without a relevant education, just as we usually cannot understand sentences in a foreign language unless we have studied that particular language).

So, unless someone wants to comment specifically on the proof (it's still an open invitation) let's jump past the proof to references 21 thru 29 of the long version: Every single one of these nine references (21-29) considers both possibilities (force on conductor and force on core) for normal torque producing force in standard machines with conductors in slots and every single one of them concludes the force acts primarily on the core. But don't take my word for it.... judge for yourself. Here are some highlights:

quote:

Ref 21 (Professor Markus Zahn, MIT):
The force on a current-carrying wire surrounded by iron is often calculated using only the Lorentz force, neglective the presence of the iron. The correct answer is obtained but for the wrong reasons. Actually there is very little B field near the wire as it is almost surrounded by the high-permeability iron so that the Lorentz force on the wire is very small. The force is actually on the iron core.

quote:

Ref 26 (Induction Machine Handbook):
the torque (due to tangential forces) is exerted mainly on slot walls and not on the conductors themselves.

quote:

Ref 27 (Austin Hughes):
With the conductors in slots, the air-gap can be made small, but, as can be seen from Figure 1.10, almost all the flux now passes down the low-reluctance path through the teeth, leaving the conductors exposed to the very low leakage flux density in the slots. It might therefore be expected that little or no force would be developed, since on the face of it the conductors are screened from the flux. Remarkably, however, what happens is that the total force remains the same as it would have been if the conductors were actually in the flux, but almost all the force now acts on the rotor teeth, rather than on the conductors themselves.

quote:

Ref 29 (Finite Element Methods in Electrical Power Engineering):
In devices such as the induction motor, with stator and rotor windings in slots, the torque producing force on the conductors is very small (though the force acting towards the slot bottom may be large). As discussed by, for example Carter (1962), the bulk of the torque forces act on the sides of the teeth.

More complete excerpts from all nine references (21 thru 29) are included in the attachment to this post (also starting on page 50 of the the long version http://tinyurl.com/ygt6azo ). Also included therein are complete bibliographic citations. Many of these nine references provide proof based on experimental evidence, theoretical analysis, or finite element analysis. Again judge for yourself, it's not difficult to see that these authors are specifically considering the same question that we are considering within this thread, and coming to the same conclusion as Jan and myself.

Howard – you claim to have proven something (force acts primarily on conductors) that contradicts all nine of the these references 21 thru 29.

Are you really claiming that:

• not only is the proof from Jan/myself incorrect (for some reasons that you have never managed to articulate)...
  
• but also the authors of all nine of these references that specifically addressed the exact same question are likewise incorrect ? ! ! ! ? ? ? ! ! ! ? ? ?

If that's what you're really saying, it would be quite an extraordinary claim imo. I would very much like to hear the substance of theory and experiment that supports any such claim (that has never been presented here on the forum). And for such an extraordinary claim, I imagine you wouldn't want to wait another three years to publish your paper.

This message has been edited. Last edited by: electricpete,

ExcerptsTrimmed3.pdf (140 KB, 10 downloads)

I strongly recommend that at the very least, folks review the short version of electricpete's proof, which is linked above. It is an easy read (just nine pages, well illustrated), and serves as a useful adjunct to the experiment which jank recently documented in his video.

I must say that I am disappointed to see virtually no response from those who had disagreed with the work of these two forum members. It is no crime to be wrong, but the lack of acknowledgement - or response of any kind - disrespects the efforts that electricpete and jank have devoted to explaining the science behind this particular issue.

Okay Jack, here is a response, although I do not disagreed the work of Jan and EP, I am just an interested watcher with a critical mind.

The rotor of a synchronous machine does not have rotor bars like a squirrel cage of an asynchronous machine. Nevertheless a synchronous machine produces rotor torque and this fact would make it obvious that the force acts on the iron. Analoguous to solid rotor motor design.
However most synchronous machines have a damper cage. Under normal conditions the damper cage bars do not carry current. Only in case of torsional instability these bars do carry current and produce a low frequent opposing torque in order to stabilize torsional vibrations.
I just wonder: is this opposing torque also not acting on damping cage bars and acting on iron only?

Regards,
Arie Mol

Jack – thanks for the kind words about my writeup.

Arie:

quote:

I am just an interested watcher with a critical mind.

I think all questions and ideas are helpful and I appreciate your interest. I think your participation has been very reasonable and helpful. The obviously-missing response/acknowledgement is from from someone who claims to have proof of a contrary position, but has not shown any proof.

quote:

However most synchronous machines have a damper cage. Under normal conditions the damper cage bars do not carry current. Only in case of torsional instability these bars do carry current and produce a low frequent opposing torque in order to stabilize torsional vibrations.
I just wonder: is this opposing torque also not acting on damping cage bars and acting on iron only?

We don’t have any sync motors at our plant. I see here a photo which shows the armortisseur conductors embedded in slots;
http://www.kilowattclassroom.com/Motors/Sync2.pdf
In general whenver the current carrying conductors are in slots (surrounded by iron on at least three sides), any torque producing (tangential) force will occur on the iron. If current-carrying conductors were located directly in the radial airgap flux, then the tangential force would occur on the conductor.

It is good to point out there are differences and the answer depends on the machine construction. The specific area of contention that we have been discussing (identified in the very first paragraph of the short and long versions… also visible in Howard and Jan's videos) is a motor with conductors in slots (which is by far the most common construction for electric motors). In that case, the iron “shields” the conductor from flux (see Figure 6 of the long version) and the radial flux at the location of the conductor is very small. Therefore (since torque-producing force on conductors is proportional to radial flux) the torque-producing force on the conductor must be very small.

This message has been edited. Last edited by: electricpete,

Below is the 4-part proof (#1, #2, #3, #4) that the normal torque producing force in a standard induction motor acts primarily on the core, which I first posted on 03 October 2006 11:18 AM:

quote:

The 4-part proof:
#1 - Tconductor = R* N *I* L* Bslot* p.f.
#2 - Tmotor = R* N *I* L* Bgap* p.f.
#3 - Bslot << Bgap ("<<" means much less than)
#4 - Combining 1 thru 3 proves Tconductor << Tmotor and therefore Tcore>>Tconductor
where:

N = number of conductors

L = length of each conductor in the slot section

I = rms value of the fundamental current in each conductor

Bslot is rms of the fundamental radial flux density in the slot section

Bgap is rms of the fundamental radial flux density in the airgap

p.f. is cosine of angle between B and I which represents a power factor

Tmotor = motor torque (sum of conductor torque and iron torque)

Tconductor = torque created by force acting directly on the electrical conductors

Tcore = torque created by force acting directly on the magnetic core

R = radius
(the disucssion applies to standard induction motors with conductors in slots)

Very detailed support of the above statement can be found in:
the short version: http://tinyurl.com/yhp6oyu
and the long version: http://tinyurl.com/ygt6azo

But I want to jump to #4 because it highlights the structure of the proof. Item #4 simply states that IF all of the previous statements are correct, THEN the conclusion reached by Jan and myself must be true. And to convince yourself of the validity of the IF/THEN logic of #4, you don't need any deep understanding of electromagnetics, all you need is simple high-school algebra:

quote:

More details on #4 (simple algebra):
#4 combines the previous three items together using simple algebra to demonstrate the conclusion Tconductor << Tmotor and the majority of the torque acts on the iron:

#1/#2 = Tconductor/Tmotor = (R N L I Bslot pf ) / (R N L I Bgap pf ) = Bslot/Bgap

Tconductor/Tmotor = Bslot/Bgap

If Bslot<<Bgap (#3), then Tconductor<<Tmotor

Since only a small fraction of the total motor torque acts on the copper conductor, the remainder of the torque (which is the majority of the torque) must act directly on the iron core.

I hope we agree on the IF/THEN logic of #4 (but would be glad to discuss it further if any disagreement). With that under our belts, it is easy to see that anyone wishing to disprove the proof must identify one of the preceeding items (#1, #2, #3) which is incorrect. That would serve to narrow down the area of disagreement and facilitate driving the discussion to a resolution, which is something we should all want, right?

After all... the answer is contained within the laws of physics (which are not subject to debate), so if we bring the discussion to a level of details of specific laws of physics, we can identify the specific area of misunderstanding. Everyone should agree that there must be a misunderstanding on one side or the other... I personally have zero doubt on which side it lies.

Howard has made a pretty good show of claiming there is something wrong with the 4-part proof:

• "The 'proof' is a little simplistic" (motordoc 04 October 2006 07:56 AM ).
  
• "I do have a lot of comments about the 'proof' identified by ElectricPete and was going to answer it appropriately....I have reviewed your material and I am fully aware of why you have your point of view, and planned on educating you further." (motordoc 06 October 2006 05:59 AM).
  
• "I can see where you are coming from and where the assumptions are made" (09 October 2006 08:02 AM ).

But guess what? In three long years... 16+ pages of threads, and in spite of Howard's boisterous comments about my proof quoted above, Howard has not articulated a single specific objection to the proof. He has not even narrowed it down to which of the 4 elements of the proof he disagrees with (#1, #2, #3, #4)! And this is not a simple oversight... as anyone who followed these threads knows, I have asked many many times for Howard to simply identify which of the 4 he disagreed with (the invitation remains open... which item do you disagree with #1, #2, #3 or #4?). All of those many requests have simply been ignored. And it is certainly not surprising to me that we have heard no response from Howard to narrow down and resolve the disagreement..... When you claim to disagree with a proof that 2+2=4, the last thing you want to do is talk specific mathematical details.

Howard has also made a lot noise about his own proofs/papers etc....each one announced ahead of time with fanfare.... each one eventually fizzled (not delivered) or exposed as incorrect/irrelevant by Jan and myself with no acknowledgement of the errors from Howard.

Let's take a look at some of Howard's previous promises of proof or attempts at proof...

On 04 October 2006 08:56 AM, motordoc wrote: "In the meantime, when I get a few minutes this weekend, I will take your challenge by putting together a motor design on paper then analyzing it. To make it even more of a challenge, I will design a smaller integral horsepower motor where there is more stator and rotor core material per horsepower than a larger, medium voltage machine (if I have the chance, I will also put together the basic design of a medium voltage, which we can also analyze)."

On 09 October 2006 08:55 PM, Howard posted an attachment labeled "Part_1_of_Solution.pdf" which can be seen here:
http://tinyurl.com/yzruvfz
and in the same post he wrote "I will be back on it as soon as I complete another project over the next day or so."

As you can see at link above, Howard's Part 1 is simply a summary of motor design data including motor rating, size, conductor configuration, etc. There is no proof of Howard's claim that force acts on the conductor. So when Jan and I pointed out there was no proof to be seen in Howards part 1,and pressed Howard for the promised part 2, we got the following responses:

On 10 October 2006 11:31 AM, motordoc wrote: "You need to start reading what I said. This is the first part of my proof, which is just the design of the motor. Determining the effects of the fields and their interaction within the rotor is not simple algebra. As I said, I will be back on this when I have the opportunity in a few days."

On 22 October 2006 04:31 PM motordoc wrote: "Been traveling. Stopped home to pick up a few references. At SMRP and will see if I can catch an hour or two to finish my proofs. Worst case, Wednesday after I return home for a few days."

On 27 October 2006 06:06 PM motordoc wrote: "My final intention was to hand-design then handdynamically analyze an electric motor. Not a simple feat that requires time that I have been trying to fit into a fairly intense schedule. Now, what I have decided is that I will complete this study as I can then post it and also generate an article on it for ReliabilityWeb"

In the last quote we see Howard finally admits there will be no part 2 that has anything whatsoever to do with the data posted in Howard's "part 1 of solution". The data in part 1 accomplished nothing other than to give the appearance over a period of a few weeks that Howard was about to provide some very detailed and specific proof.... but Howard never posted anything whatsoever that built upon the motor data in part 1.

Before we leave Howard's part 1,there are some very important points to note. Among the standard motor design data posted in Howard's Part 1 are flux densities at 5 different locations (gap, stator backiron, stator teeth, rotor backiron, rotor teeth), but none of them in the slot. These are standard locations to consider/calculate flux densities used in motor design, and it is not surprisng to me that Bslot is omitted, since since flux density in the slot is not important for torque producition (my equation #2 does not depend on Bslot). But if you are going to calculate the motor torque using a force on conductor equations (F= q V x B = L I x B) as Howard suggests, then you'd darned well better know the flux desnity B at the location of the conductor (Bslot)! But Howard doesn't even list that among his deisgn data! I pointed this contradiction out to him on 10 October 2006 06:32 AM, but there was never any response (other than to suggest it would be addressed in Part 2... which never materialized). To this day he has not explained how he is going to compute force on the conductor (which is the only relevant torque-producing force in his theory) from his design data without knowing the flux density at the location of the conductor which is inside the slot. On the other hand, I myself have incorporated the exact design data from Howard's "Part 1 of solution" into my own "Long Version" section 12.4.1 – "Cross-check of part #2 by calculation with example motor data". (see above for link to "The Long Version") Using the equation corresponding to item #2 of my 4-part proof (Tmotor = R ·N ·L ·I ·Bgap ·pf), I calculated a total motor torque which matched rated torque to within a few percent. And of course item #2 does not represent the force on the conductors since it uses Bgap, not Bslot. The actual force on conductors must be lower than my #2 by a fraction Bslot/Bgap since the conductor is located in flux desnity Bslot, not Bgap.

Howard never posted a part-2-of-solution building on his "part 1 of solution", but he said he would post an article on ReliabilityWeb....and indeed he did. He posted a whitepaper on reliabilityweb and attached the same whiatepaper on the forum entitled "Forces on the Rotor Bars of a Three Phase Induction Motor". The whitepaper was presented with great fanfare as if Howard had proven his point. Here is a copy:
http://tinyurl.com/ybqv74s

There are at least two major flaws I have identified in Howard's whitepaper linked directly above:

1 – The majority of the discussion (figures 1 through 4) center on devices with conductors NOT located in slots. Anyone paying attention to the discussion already knows that the conductors will experience drastically different flux densities and forces depending on whether or not they are in a slot.. Howard himself has admitted admitted (27 October 2006 06:06 PM) that the magnetic field at the location of the conductors in slots is "virtually zero". Since force on a conductor is proportional to magnetic field (flux desnity), it's not too hard to figure out that the dramatic change in flux desnity associated with moving a conductor from airgap to slot translates directly to a dramatic change in force on the conductor.

2 – The "Conclusion" section of Howard's whitepaper states "As shown in Figure 8, the stator has laminations, the rotor core is constructed in the same way. In order for the forces to work directly in the rotor teeth, the rotor core teeth would have to be solid, not laminated." Howard's statement that magnetic force cannot act on laminated iron is incorrect. You can easily prove this for yourself by taking a simple permanent magnet and holding it next to a laminated iron core (there will be force even though the core is laminated). I will be glad to post a video of this simple experiment if anyone doubts the results (do you want the video Howard?). The reason that magnetic force occurs even on a laminated core is that the relevant mechanism for force on the iron has nothing to do with any circulating current within the iron.
Further details on these points and others is given in my "rebuttal" to Howard's whitepaper. My rebuttal is available here:
http://tinyurl.com/ygtgutj

Howard never acknowledged these fundamental errors in his whitepaper that were pointed out by my rebuttal. However I notice his whitepaper no longer appears on reliabilityweb. In fact, as far as I can tell from google search for the paper, it no longer exists anywhere on the web except my own website. I don't want to read too much into this, but I would be interested to hear from Howard any comments about what happened to his whitepaper.... is it available on your website? If not, is there some reason you don't want it displayed?

That brings us almost up to date to 2009. Now on three recent occasions in 2009 within threads on subjects unrelated to torque-producing force, Howard brought up the subject of torque producing force. (Does anyone else find it strange that he was so eager to bring up the subject of torque-producing force out of the blue in threads on other subjects, but suddenly gets very quiet when there is a thread specifically on the subject with questions addressed specifically and directly to him?).

As I have outlined in my own post 08 October 2009 11:59 PM of the present thread, Howard is now referring to his video as "proof" of his position. The gaping holes in Howard's latest proof/video are obvious (as Jack figured out) if we simply use our eyes to watch the video instead of using our ears to listen to what Howard and his coworker are saying ("The core did not move....Nope, the core did not move"). When this obvious flaw was pointed out (my post 08 October 2009 11:59 PM of the present thread), there was no direct response or acknowledgement from Howard. In fact, there was the exact opposite of an acknowledgement.... Howard called my comments about the video "excuses"! Apparently Howard expects us to believe what he says without questioning, even when our eyes tell us otherwise!

Having seen the way Howard operates on the forum over a period of many years, I am certainly very skeptical about anything that comes out of his mouth/keyboard. But this disussion about the video is not a matter of being overly-skeptical, this is just a matter of simple common sense. I don't think anyone on the forum is gullible enough to believe someone else's words over their own eyes!

Now we are again at a point where all of the previously-presented proofs from Howard have been discussed and debunked (if there is dispute over any of my previous comments I would be glad to discuss the specifics). But we still have vague mention of some future proof that Howard intends to provide. But let's remember all the promises of proof we heard before that were flawed or never materialized as quoted earlier in my post. And let's not forget this gem from more than three years ago:

motordoc wrote 29 October 2006 06:41 PM "I am going to put this together as a paper referreed by my peers. That paper will be posted in a separate area at a separate time, and will include the conclusions as I find them."

Guess what. That was 3+ years ago and there has been no peer-reviewed paper. There is a reason that 3+ years have passed without a peer-reviewed paper. I am 100% confident that Howard will never produce any peer reviewed paper to prove his claim. You can see already many peer-reviewed and other reputable references proving the exact opposite among references 21-30 of the long version (excerpts included at the end of the long version linked above). And if you want to prove that 2+2=5, a peer-reviewed paper is not the place – you cannot ignore the tough questions that inevitably will follow.

But unfortunately, it's easy to make such claims in a forum like this where you can make excuses to ignore the tough questions. It's particularly easy in a typical thread that fades away within a few days – you can evade questions about proof under the pretense that proof will be provided at some future time and in some other venue.

But time has a way of bringing out the truth. When the promises of future proof are repeatedly either not delievered, or delivered with obvious flaws, the promise of future proof eventually starts to ring very hollow.

The proof offerred by Jan and myself (#1, #2, #3, #4) is not some vague dubious future promised proof. It is a real proof that has been shared out in the open in broad daylight.... posted on the forum over three years ago with open invitation for discussion. During all that time, it has never been contradicted.

I would certainly be interested to address any questions or objections to what I have written. (I'm sure Jan would as well).

This message has been edited. Last edited by: electricpete,

Howard, are you out there? The silence is deafening.

The goal of the forum is to promote learning. There are bound to be disagreements – it comes with the territory. But we rely on professional discussion conducted in good faith in order to reach a resolution of those disagreements, so that everyone can benefit from that resolution.

Here we have a misleading video promoted by Howard as “proof” of his position, which relies on listening to what the people in the video say (“the core did not move”) rather than what we see with our own eyes in the video (the core did move). When this discrepancy was questioned (my post 08 October 2009 09:59 PM of this thread), there was no explanation for the discrepancy, only an attack on the questioner (my comments/questions were labeled as “excuses” in Howard's post 13 October 2009 02:05 PM).

In Howard’s whitepaper http://tinyurl.com/ybqv74s , we have incorrect comments published in the conclusion: “As shown in Figure 8, the stator has laminations, the rotor core is constructed in the same way. In order for the forces to work directly in the rotor teeth, the rotor core teeth would have to be solid, not laminated." When that error was pointed out, it was never acknowledged, it was never addressed, it was never corrected... instead it was simply ignored.

We have from Howard no response to the 4-part proof supporting my position and Jan’s position, outlined here:
the short version: http://tinyurl.com/yhp6oyu

We have from Howard no response to the detailed justification for the 4-part proof AND supporting references (references 21-30) with lengthy excerpts here:
the long version: http://tinyurl.com/ygt6azo

After three years, we don’t even know which part of the 4 part-proof is supposedly wrong (#1, #2, #3 or #4?)!!?!! Wow.

This does not seem like a good faith effort to get at the truth in my opinion.

If the strategy is to ignore the subject into oblivion simply to avoid embarrassment, I will not be an enabler of such strategy.

I will keep bumping this thread to the top once per calendar month until it is resolved.