Rotating Magnetic Field's and Inductors.

[MileHigh]

I have always been happy to carry out experiments as requested--even though MH seems to have missed the timing experiment results posted some time back on this thread.

Brad

You are trying to equate whatever timing information you have posted with my request for a timing diagram for the motor.  You have not presented anything even remotely close to a timing diagram as I have described it over many postings.

[citfta]

You take a motor and measure 100 electrical watts in, 95 mechanical watts out, and 5 watts of waste heat.  Now where do you think the power came from to make the motor output 95 watts of mechanical power?

Those are the facts.  If you willfully chose to ignore the facts I don't know what to say.


MileHigh

That answer has absolutely nothing to do with the question.  I'll repeat the question.  Maybe you'll get it this time.  If magnets can't do any work then why has industry switched over to using permanent magnets instead of field coils in almost all smaller DC motors?

Now to answer your question.  The output power of 95 watts mechanical power came from the interaction between the armature and the permanent magnets.  If you take the magnets out you will get no mechanical power from that motor.  Seems pretty simple there must be something those magnets are doing.

Carroll

[MileHigh]

@ MH

Now lets look at the peak current flow with and without the rotor.
Is it not clear that the peak input current flow without the rotor is higher than it is with the rotor--and yet,the peak current flow on the P/out side remains at the same value in both cases,but continues to flow for a longer period of time with the rotor in play,as can be seen by the dime duration on the yellow voltage trace.

So i ask once again,how can this be if it is not the inductance of the coil rising?.

Brad

Okay, for starters let's delve into the concept of the inductance of the coil "rising."

The coil has a core of a certain material and a wire of a number of turns and the coil cylinder has a length, inner diameter and outer diameter.  You can crunch the numbers on the Hyperphysics web site and get the inductance of the coil.  Note these are parameters that are fixed and never change.  Let's call that the "basic inductance" of the coil which does not change.

Then when you put the coil in a pulse motor, external factors will modify its electrical behaviour and give it a higher or lower "apparent inductance."  For example, if the coil pulses and pushes a magnet away, the current rises more slowly and gives the coil a higher apparent inductance.  But can you recover the energy in the back spike corresponding to the higher apparent inductance? The answer is no.  You can only recover energy in the back spike that corresponds to the basic inductance.  The rest of the energy that you want to recover from the apparent inductance is now tied up in the mass of the moving magnet.

Now to deal with this:

the peak current flow on the P/out side remains at the same value in both cases,but continues to flow for a longer period of time with the rotor in play,as can be seen by the dime duration on the yellow voltage trace.

I agree that you can see that the current discharge is longer in the case where the rotor is in place.  So in this case it looks like the inductance really did increase and it looks like I am contradicting myself with respect to what I just said above.

But one more time, we are looking at two separate and distinct cases and they can't be compared.  I don't know why the back spike discharge is longer when the rotor is in place.  However, I can just make a guess.  The guess is that during the back spike discharge the moving rotor magnet is coupling power through the coil.  In other words, we are back to the theory that the rotor picks up energy at the start of the energizing cycle, and then gives up some of that energy during the kick back portion of the cycle.  This goes right back to what Picowatt said.

If you had a proper timing diagram you could investigate this and see if it was true.  If it was true you could annotate the timing diagram with a note and an arrow pointing to the discharge cycle.  The note would say, "Rotor coupling extra energy into back spike discharge cycle due to transformer action between moving rotor magnet and coil."

Instead of explaining what is happening, your "explanation" is "the inductance of the coil is rising."

MileHigh

[MileHigh]

That answer has absolutely nothing to do with the question.  I'll repeat the question.  Maybe you'll get it this time.  If magnets can't do any work then why has industry switched over to using permanent magnets instead of field coils in almost all smaller DC motors?

Now to answer your question.  The output power of 95 watts mechanical power came from the interaction between the armature and the permanent magnets.  If you take the magnets out you will get no mechanical power from that motor.  Seems pretty simple there must be something those magnets are doing.

Carroll

Your logic is wrong.  There is no point in comparing two different types of motor.  I am pretty sure that older motors were made on the cheap and people were not concerned with energy consumption.  More modern motors are more expensive and more efficient because people are concerned about energy consumption.

They are just two different types of motors.  Both types of motors get their ability to output mechanical power directly and exclusively from the input electrical power.  The magnets are just a component that goes into building one of the motors and are as dead as a doornail.  The magnets don't "push" they are pushed upon.

If you refuse to accept this then let's just agree to disagree.

[citfta]

I can respectfully agree to disagree.  But I do have one more question.  If the magnets are only pushed against and don't return the push then why can't we just use something else to be pushed against?

Carroll