Rotating Magnetic Field's and Inductors.

[picowatt]

Eddy currents--Quote: In a transformer, the magnetic flux created by the primary coil induces a current in the core. This occurs in order to oppose the change that produced the magnetic flux (Lenz's Law). The currents flowing in the core are called eddy currents. These currents produce heat, using up energy and so causing inefficiency.

So,we know that it is the magnetic flux that creates these eddy currents,so if an approaching permanent magnet of the right field orientation induces eddy currents into the core before the current starts to flow through the winding's,then once the current dose start to flow through the windings,the eddy currents have already been produced within the core from the approaching magnet--and so no electrical power is wasted in producing these eddy current's,as they already exist. I believe eddy currents are the result of the magnetic domain alignment,and our PM has already aligned these domains.

Then you had to waste mechanical power by using the approaching PM's to produce eddy currents, which will also produce a magnetic field in opposition to your approaching PM's.  Either way the production of eddy currents degrades efficiency.  Hence, all efforts are made to reduce or eliminate eddy currents.

Sure,have all the coffee you like,but answer with your own thoughts,and not those biased toward an untruth that agree's with the good old book's of yesty year. They are not hard question's,and deserve a straight forward answer.

Well that's a lot of "attitude" for so early in the morning...

Regarding your questions:

1--has useful work been done,or has work been done when heat is converted into electrical or mechanical power?

Please keep in mind that I do not claim to be a physicist and that there are likely others here more properly suited to answering this question precisely as it is given.  However, because you used the word "power", I would say yes.

2--do we or do we not convert heat into mechanical power that is added to the output of the motor,or into electrical power that is added back into the supply power when the stator electromagnets are replaced with permanent magnets?.

I would say we do not.  Although using the permanent magnets "eliminates" Joule heating caused by I²R losses, there is no "conversion" of any heat into something else taking place.

3--is there any other way you know of to convert the waste heat from the stator coils into either electrical or mechanical energy other than permanent magnets (added to make clearer)-->where there is no loss incurred,or no work being done.

As per number 2, I don't see any "conversion" taking place.  Since what you are eliminating is I²R losses by using PM's, anything that reduces "R" to zero would work as well.  Although a bit impractical at this time, as a thought experiment, superconductors come to mind.

And 4--are the stator coils doing work in a universal motor?.

This is a good question.  The conundrum I am having with arriving at the answer is that they are "stator" coils.  When I accelerate my car, pushing off against the road so to speak, is the road doing work to move my car? 

PW

ADDED:  With regard to question one, I see you used the term "useful work".  I may have to reconsider my answer after I go back and look at how you defined "useful work".

[tinman]

 

PW

Then you had to waste mechanical power by using the approaching PM's to produce eddy currents, which will also produce a magnetic field in opposition to your approaching PM's.  Either way the production of eddy currents degrades efficiency.  Hence, all efforts are made to reduce or eliminate eddy currents.

Not true PW. If an apposing field was produced by the core,then the magnet would not be attracted to it. The field at the core end nearest to the approaching magnet will be the opposite field to that of the magnet,as like fields do not attract.

Well that's a lot of "attitude" for so early in the morning...

Regarding your questions:

There was no attitude intended PW,maybe more a culture differential ?
I just posted my thought's. I have been asked by many to carry out test as per there specifications many times on many devices,and i have done that to the best of my ability. I only ask the same of you-to answer what !you! know to be true,and what makes sense to you.

Please keep in mind that I do not claim to be a physicist and that there are likely others here more properly suited to answering this question precisely as it is given.  However, because you used the word "power", I would say yes.

i hope you have kept in mind that power as i mentioned can also be output power--as in HP,or KW-mechanical.

I would say we do not.  Although using the permanent magnets "eliminates" Joule heating, there is no "conversion" of any heat into something else taking place.

This answer go;s against your first answer--and i will explain at the bottom of this post.

As per number 2, I don't see any "conversion" taking place.  Since what you are eliminating I²R losses by using PM's, anything that eliminates the "R" would work as well.  Although impractical, as a thought experiment, superconductors come to mind.

I would have to say that a super conductor is not right PW--unless you know of a room temperature super conductive material ?. If not,then energy is required to keep the super conductive material at temperatures where it becomes super conductive.

This is a good question.  The conundrum I am having with arriving at the answer is that they are "stator" coils.  When I accelerate my car, pushing off against the road, so to speak, is the road doing work?

I think this analogy is a bit wrong.
The road would be your motor housing,the wheels your stators,and the engine your rotor.
If we look at it like this,are your wheels doing work ?.

OK,answers 1 and 2
Question 1--1--has useful work been done,or has work been done when heat is converted into electrical or mechanical power?
Answer--However, because you used the word "power", I would say yes.

Question 2--do we or do we not convert heat into mechanical power that is added to the output of the motor,or into electrical power that is added back into the supply power when the stator electromagnets are replaced with permanent magnets?.
Answer--I would say we do not.  Although using the permanent magnets "eliminates" Joule heating, there is no "conversion" of any heat into something else taking place.

Lets have a look at what happens here when we swap out the stator coils for PM's.
Lets say the two stator windings consume 1/2 the amount of power as the rotor,and we have a power draw of say 3 watt's--1/2 a watt for each stator winding,and 2 watts for the rotor(these are just example figures) As each of the stator windings have a DC current flowing through them,we can assume that each stator is dissipating 1/2 a watt of heat energy. So our motor will be a little lower that 66% efficient due to the heat loss also in the rotor. Anyway,so we are putting in 3 watts of power,and loosing !lets just stick to 1 watt! of power by way of dissipated heat. So now we replace the two stator windings with ceramic magnets of the same magnetic strength that the stator windings provided. We now have dropped the P/in by 1 watt. So as to keep the P/in the same,we can now put that 1 watt into the rotor,so as we keep our 3 watt P/in. Do we now have the same mechanical power output,or do we have more? If we have more,has not the instalation of the PM's converted/transformed the 1 watt of waste heat into mechanical power--as our P/in has remained the same. And the second gain(although unwanted)is now that the rotor has more power being delivered to it,will it also not dissipate more heat energy?

So by removing the stator coils,and installing the PM's,we have converted that waste heat from the stator coils into mechanical output power,and also increased the heat energy dissipated by the rotor--all while maintaining the same P/in. If it was not the permanent magnets that made this transformation/conversion possible,then what was it?

It is said-in order to show that permanent magnets are doing useful work,you must show an energy gain when those magnets are put into place within the system.
Did we not just do that?


Brad.

[tinman]

Then you had to waste mechanical power by using the approaching PM's to produce eddy currents, which will also produce a magnetic field in opposition to your approaching PM's.  Either way the production of eddy currents degrades efficiency.  Hence, all efforts are made to reduce or eliminate eddy currents.

Well that's a lot of "attitude" for so early in the morning...

Regarding your questions:


Please keep in mind that I do not claim to be a physicist and that there are likely others here more properly suited to answering this question precisely as it is given.  However, because you used the word "power", I would say yes.

I would say we do not.  Although using the permanent magnets "eliminates" Joule heating caused by I²R losses, there is no "conversion" of any heat into something else taking place.

As per number 2, I don't see any "conversion" taking place.  Since what you are eliminating is I²R losses by using PM's, anything that reduces "R" to zero would work as well.  Although a bit impractical at this time, as a thought experiment, superconductors come to mind.

This is a good question.  The conundrum I am having with arriving at the answer is that they are "stator" coils.  When I accelerate my car, pushing off against the road so to speak, is the road doing work to move my car? 

PW

ADDED: 

With regard to question one, I see you used the term "useful work".  I may have to reconsider my answer after I go back and look at how you defined "useful work".

Useful work in that quotation means taking a waste energy(heat) and converting it into a wanted(useful) energy (electrical or mechanical power)

[picowatt]

Not true PW. If an apposing field was produced by the core,then the magnet would not be attracted to it. The field at the core end nearest to the approaching magnet will be the opposite field to that of the magnet,as like fields do not attract.

If your core is ferromagnetic, very likely attraction will overcome the repulsion produced by the eddy currents.  Try spinning your rotor near a sheet of copper and see what the induced eddy currents do for you.  I believe the eddy current thing is a non-starter and only produces losses.

i hope you have kept in mind that power as i mentioned can also be output power--as in HP,or KW-mechanical.

This answer go;s against your first answer--and i will explain at the bottom of this post.

I would have to say that a super conductor is not right PW--unless you know of a room temperature super conductive material ?. If not,then energy is required to keep the super conductive material at temperatures where it becomes super conductive.

Hence my "not practical at this time" and "thought experiment" comments.  However, the results would be similar.

I think this analogy is a bit wrong.
The road would be your motor housing,the wheels your stators,and the engine your rotor.
If we look at it like this,are your wheels doing work ?.

I believe my analogy was just fine as it was.  If the road is the "motor housing" as you put it, is not the stator firmly attached to that housing?

As well, if I am a swimmer pushing off against the wall of a pool, is the pool wall doing work to accelerate me? 

Lets have a look at what happens here when we swap out the stator coils for PM's.

I understand what you are saying, but again, although you are "eliminating" a source of heat, no heat is being "converted".  If I swap out my incandescent bulbs for LED's, are my LED's converting heat into something?  I say no.  Depending on whether I choose to increase or decrease the input, I can achieve the same light output for less input, or more light output for the same input.  The use of LED's has increased the input/output efficiency but nowhere in the LED is heat being converted into something else (ignoring the heat generated by the LED of course).

I am not arguing against the increase in efficiency by using PM's, just the idea that heat is somehow being converted by the PM's.  You can choose to produce the same HP out for less input or more HP out for the same input.  But again, there is no mechanism converting heat into something.,   

It is said-in order to show that permanent magnets are doing useful work,you must show an energy gain when those magnets are put into place within the system.
Did we not just do that?

There you go with the "useful work" phrase again...  Do you mean to say non-conservative or perhaps just work?

In any event, measurements accepted, the spinning rotor test had a 40% or so efficiency without the rotor, and something better with it.  What was seen was a decrease of the system's inefficiency (or increase of efficiency if you prefer).

Other modifications could also improve the efficiency, possibly more so than the PM's, but the constraints you placed on your definition of "useful work" does not allow those improvements to be considered useful work.

If the core of your inductor was replaced with ferrite to eliminate all eddy currents in the core, would that not qualify as "useful work" per your definition?  All losses by that particular mechanism would be eliminated, not just reduced...   

PW

[gyulasun]

How can the same input energy to an electromagnet exert higher pushing force on a body with higher mass compared to a body with a lower mass? 

Is this a trick question? I believe you answered yourself below...

Of course we know that the bodies are that of a ceramic (15 gram) and Neo (50 gram) magnets which have differing magnetic strengths.
   

Hi poynt99,

Well, it was not intended a trick question. I gave a hint only by mentioning the differing magnetic strength of the magnets used in the video test.

If you agree, we could examine what really happens in the repel interaction between the electro and the permanent magnet. It looks like as if either the magnetic flux from the coil (while receives the same input energy) would exert more repel force against a stronger permanent magnet than against a weaker one or the stronger permanent magnet field would react with a stronger reaction force it received.

A coil (an air cored multilayer solenoid in this test) should always produce the same magnetic field strength at its poles whenever it receives the same input current which is the case in the tests. Yet the stronger permanent magnet he used, the higher the repel force became as a result of the interaction.

Can we consider this test as an example for Newton 3rd Law? If yes, why is it that while in the tests the action force is always the same,  the resulting force from the interaction gets higher as if the resulting reaction force would get also higher?
This is what we can observe in the tests, right?

A mechanical spring is often used as a comparison when permanent magnets are discussed, in this test case we would have two springs with differing mechanical strengths. Then giving a certain press force to the weak spring from outside, and then releasing it, it would exert quasi the same pushing force (like the press force was) to the strong spring, right? And the strong spring would 'absorb' the given amount of push and would react with an equal counter force, correct?  However it looks like the strong spring would react with a stronger force than it received if we continue the comparison to the tests with the magnets.

I would read your thoughts on these with interest. Maybe I have not considered something important in my 'reasonings'.

Gyula

PS  this is the link to the video with the tests for those who have not yet seen it:  https://www.youtube.com/watch?v=9kCkROMSGG0