MH's ideal coil and voltage question

[poynt99]

As i said, the CEMF cannot be equal to the EMF like it is with the ideal coil.

And as I said, yes it is equal with a real coil too, at t=0.

What i ment by current flow not being limited,was to that like the ideal coil,where the current is !apparently! limited to 800mA /second. As the winding resistance increases,our current trace follows a greater curve.

BOTH the ideal and real coils will be restricted to 0.8A/s maximum rate of current rise if they are 5H inductors, and free of parasitic capacitance. It is interesting that you refer to the ideal coil as being limited, when in fact the real coil is more limited because it hits a maximum current and its rate of rise decreases over time, whereas the ideal coil does not.

[poynt99]

Here is the real coil (R=1 Ohm) voltage tradeoff traces.

At t=0 ALL the voltage is across the inductance, and 0V across the resistor. That is, at t=0, cemf=emf. And yet, current flows.

After 30s or so the inductance ends up with 0V, and the resistance 4V across them; they have traded places.

[partzman]

But then, perhaps not...

Partzman,

There was no "math fudge" needed, everything worked perfectly just as it was.

As for your new model that apparently requires 3 separate types of EMF, you've completely lost me...

Your notation "D", in particular, is most confusing.

PW

This model was an attempt to make sense of the Emf/Cemf feed back loop and D) represents said attempt. Do not be confused by your thought that I don't understand what you are saying because I understand completely, I just don't agree! I knew that my new model was not correct when I created the two Emf sources.

So, in another approach to resolve the matter, I propose we attempt to simulate the inductor that is, not use the internal inductor model(s) in any given simulator, but break it down into functional components as Webby suggests. 

LtSpice is my preference and it's toolbox includes arbitrary behavioral voltage and current sources plus voltage dependent current sources , current dependent voltage sources, etc, so all we need to do is basically establish the model and the math.

I see no reason why this should not be doable and it would be a great teaching tool.

I have attached a schematic that shows the general circuit we wish to simulate and what I believe to be your equivalent model, but I would like you to confirm or indicate any changes that should be made so we can proceed. I am still working on my own equivalent model and will post it as soon as it is complete enough for criticism.

pm

[tinman]

Here is the real coil (R=1 Ohm) voltage tradeoff traces.

At t=0 ALL the voltage is across the inductance, and 0V across the resistor. That is, at t=0, cemf=emf. And yet, current flows.

After 30s or so the inductance ends up with 0V, and the resistance 4V across them; they have traded places.

Either your sim dose not represent an accurate description of what happens at T=0,or you are not looking closely enough.

At T=0,the current will rise with the voltage until such time as the capacitance of the windings has been charged. depending on capacitance value,the current will !after a short time! return to a 0 value,and then begin it's rise over time.

At T=0,the CEMF dose not equal the EMF,as at T=0, the current tracks vertical with the voltage,and then drops back to a 0 value. The time span is very narrow,but it is at and after T=0.


Brad

[tinman]

This model was an attempt to make sense of the Emf/Cemf feed back loop and D) represents said attempt. Do not be confused by your thought that I don't understand what you are saying because I understand completely, I just don't agree! I knew that my new model was not correct when I created the two Emf sources.

So, in another approach to resolve the matter, I propose we attempt to simulate the inductor that is, not use the internal inductor model(s) in any given simulator, but break it down into functional components as Webby suggests. 

LtSpice is my preference and it's toolbox includes arbitrary behavioral voltage and current sources plus voltage dependent current sources , current dependent voltage sources, etc, so all we need to do is basically establish the model and the math.

I see no reason why this should not be doable and it would be a great teaching tool.

I have attached a schematic that shows the general circuit we wish to simulate and what I believe to be your equivalent model, but I would like you to confirm or indicate any changes that should be made so we can proceed. I am still working on my own equivalent model and will post it as soon as it is complete enough for criticism.

pm

Pm

Do you have a scope,or access to one?


Brad