Rotating Magnetic Field's and Inductors.

[MileHigh]

MileHigh,

You and I had a few discussions a few years ago.  At that time I mostly agreed with the things you posted.  What happened to you?  Your posts in this thread don't make any sense.  You allude to some kind of error about timing and never explain what that has to do with anything.  When Brad says there is no timing change you ignore that and in a very condescending way tell him he should always know that you are right.  Huh?  Say what?  None of us are ALWAYS right.  If you really have a technical explanation for what he is seeing then please explain.  Otherwise posting nothing at all would be a better option.

Respectfully,
Carroll

I clearly am not saying that I am "always right" and what I am saying makes perfect sense.  I am not going to explain anything, I would just be repeating stuff that I have already said 50 times before.

It's time for the experimenters to figure out things for themselves, to challenge themselves.  Working on the problem and arriving at the proper conclusion would be the best thing that could happen here.

[verpies]

What are you talking about???
The timing never changes,as the transistor is being triggered by my function generator at 37 hZ.

The word "timing" does not only mean frequency and the time when a pulse begins (like the timing of a spark in a gasoline engine) - in electronics it also means how the entire signal varies in time and how it varies in time compared to other signals.

I am sure MH meant the above.

[MileHigh]

That attitude would be contrary to the principles of the scientific method.

It's just another method at arriving at a proper conclusion, an exercise in deduction.  I arrive at conclusion "A" and then someone tells me that I am totally wrong and there is another conclusion.  If I am going to assume for the sake of argument that what this person told me is correct, then I can start over and try to reason things out.  If my reasoning results in my arriving at the same conclusion "A" then I have developed an argument to back up my statements.  However, if I follow a new path that takes me to a totally different conclusion that refutes my original conclusion and my peers agree with me and we have a consensus, then that is a very worthwhile exercise for myself and my peers.  The new conclusion may also be in accord with the unmentioned conclusion that the other person has.

In summary, I will have developed a completely new line of reasoning that hopefully is correct and refutes my original conclusion, and I hopefully will have learned something at the same time.

That's the point.

[citfta]

Hi Brad,

Looking at the still scope shots you can see that the applied voltage going to the coil does not cause the current to reach the saturation point  when the magnets are in use.  If you look at the same shot without the magnets you can see the top of the curve start to flatten just before the voltage is cut off.  This indicates the coil current has almost reached the saturation point.  So this does confirm the magnets are affecting the inductance of the coil.  You can also see the discharge time is longer when the magnets are spinning past the coil.  Hope these ideas help some as we learn about magnets and coils.

Carroll

[verpies]

I am also guessing that taking the average readings over time in the same way for both does not then reflect on the power dissipated over the time of observation

In a general case you are correct.
Mean current and mean voltage are useless for general power calculations ...yet that is what most multimeters display.

However, in the special case, when the DUT is supplied by a constant voltage (v), then the instantaneous input powers are:
v*i₁ ,  v*i₂ ,  v*i₃ , ...... ,  v*i_N
where i₁ ,  i₂ ,  _i3 , ...... ,  i_N   represent the successive input current samples_.

...and the mean input power is:
(v*i₁ + v*i₂ + v*i₃ + ...... +v*i_N) / N
or
v*(i₁ + i₂ + i₃ + ...... +i_N) / N

Note, that the term:
(i₁ + i₂ + i₃ + ...... +i_N) / N
is the arithmetical mean of the current. Let's call it i_MEAN

so we can write, that the mean input power is:
P_MEAN = v * i_MEAN
...as long as v is constant.

This formula works even when the current is negative.  Positive voltage and negative current mean that energy is returned to the power supply (C.V. source).

Note that this formula does not work when the DUT is supplied from a variable voltage source (e.g. PDC, AC, DC+AC)
For those other cases, these methods of power measurement and calculation should be used.