Back-EMF/Induced Voltage question?

Thread Starter

wes

Joined Aug 24, 2007
242
maybe this will make it easier

Will a coil turning on close to a Electromagnet that is already on cause a voltage change in the steady state Electromagnet or will it just cause a change in the Electromagnets magnetic flux and induce no voltage change
Will 2 cause a change in 1? is this simple enough


1 / 2
ON / Turning On
I---I / I---I
I---I / I---I
I---I / I---I
/
 

Thread Starter

wes

Joined Aug 24, 2007
242
well I anwsered it. It seems as though it will effect coil b.

I used a transformer setup since I figured that would show the greatest effect.

I tried setting the different coils as coil a and the other as b.

Still, it did not seem to matter in both scenarios there was an effect. When the larger turn coil was a and the smaller b, the effect was less.

When it was switched, the effect larger due to, I believe, coil b was producing a stronger field and thus the effect should be greater.

Any thoughts?
 

thatoneguy

Joined Feb 19, 2009
6,359
Two inductors next to each other will influence each other depending on the amount of magnetic coupling there is between them.

In a transformer, a magnetic field responsive core is shared between the two coils wound physically parallel to each other in order to create maximum coupling.

On a circuit board, inductors are mounted physically perpendicular to each other (one in the up-down plane, and one in the left-right plane, another in the vertical plane) to reduce undesired magnetic coupling. This is shown strongly in RF receivers, where the inductors are mounted inside Faraday cages (metal cans).

Does this answer your question, or even touch on what you are trying to ask?
 

t_n_k

Joined Mar 6, 2009
5,455
Discussing the outcome probably requires putting some values into the scenario and either doing the test or some calculations or running a simulation.

I did the latter since it involved the minimum expense and mental gymnastics.

I modeled a 1:1 "ideal" transformer of magnetizing inductance 50mH with a symmetrical square wave primary drive and secondary with a series DC bias and load resistance.

The primary simply "sees" the effective reflected secondary load resistance in terms of the observed primary current flow. The secondary DC bias has no effect on the primary conditions. [it's an assumed ideal transformer - so no saturation]. The secondary current form is the same as the primary current [as expected with 1:1 transformer] but is offset or biased by the DC bias source. If the load is 1Ω and the bias voltage is 10 volts then the secondary current is offset by 10A - positive or negative depending on the bias source polarity with respect to the transformer connection "polarities".

I should add I also included some primary resistance and ran the simulation until the circuit reached "steady state" with the square wave drive.

With this approach you can test as many scenarios as you wish. Such as changing the primary to secondary turns ratio, etc.
 
Last edited:

R!f@@

Joined Apr 2, 2009
9,918
why do people just don't seem to understand that they cannot make more energy from less.
Energy does not work that way, well at least for now.
 
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