Question regarding flux speed and transformer operation

[void109]

I've been thinking about transformers and flux, and I wanted to share some thoughts and questions to see if anyone would kindly clarify some issues.

Nothing travels faster than the speed of light (supposition), including flux.  So flux can only travel at roughly 1 foot per ns.  In a transformer when you pulse the primary, it induces a magnetic field which induces current on the secondary.  The secondary then induces its own magnetic field in opposition to the primary.  I think this is what we call BEMF and a manifestation of Lenz law?

All of the transformers I have seen are relatively small.  Given the speed limit on flux - wouldn't simply having a sufficiently large transformer core along with a sufficiently short pulse on time and dead time, avoid the penalties mentioned above?

Thanks in advance!

[mscoffman]

Signals in magnetic fields are probably a lot like electrical
signals. The signal wave front has to pass back and forth
several times at the speed of light between the source and
the load before the energy of the signal becomes unavailable
at the source and is available at the load. This is how the
real world implements conservation of energy "accounting" in
relativistic systems. It's really the basis of Quantum Mechanics
in physics, and all part that pesky "Real World".

A Pulse also has TIMOWTDI - theres more than one way to do it.
If the pulse isn't accepted magnetically it can always become
active as EMF and radiate as a radio wave.

:S:MarkSCoffman

[void109]

I'm feeling often of late, that I really should step back from all of this gadgeteering in OU research and spend a year studying physics and quantum mechanics.  I get the impression that much of what I feel is mysterious and new is actually well understood and documented.

I did notice you said "probably a lot like", instead of "is a lot like".  I have a reel of metglas tape I picked up off of ebay awhile back.  I may wrap a large magnetic track, large enough that I can use small pulse times (a magnetic circuit that is meters in diameter and pulses that are < 1 ns) and test the notion.

[gyulasun]

...
  In a transformer when you pulse the primary, it induces a magnetic field which induces current on the secondary.  The secondary then induces its own magnetic field in opposition to the primary.  I think this is what we call BEMF and a manifestation of Lenz law?

Yes.

All of the transformers I have seen are relatively small.  Given the speed limit on flux - wouldn't simply having a sufficiently large transformer core along with a sufficiently short pulse on time and dead time, avoid the penalties mentioned above?

Your question brings up in my mind a very interesting answer on getting around Lenz law. I managed to find it in the Sweet-VTA yahoo group, see this link:
http://tech.groups.yahoo.com/group/Sweet-VTA/message/4583

If someone cannot see it, here is the text, first the question, then the answer:

-----------------------------------------------------------------------
Really confused about Lenz Law
>
> Hey Yall,
>
> I'm really confused about Lenz's Law. If you place a solid permanent
> magnet through a coil, the coil will produce a magnetic field that
> opposes the magnetic field of the magnet. But, isn't this simply due
> to the fact that magnetic fields flow in a circle from North to South
> pole? Inside the structure of the permanent magnet, magnetic field
> lines flow from South to North, but outside the magnet they loop back
> around and flow from North to South. What gives?
>
> If we placed a coil through a hollow cylindrical permanent magnet,
> wouldn't induction produce a magnetic field that sucks the coil in,
> at least so far as center of the hollow cylinder?
>
> Confused,
> Ed
--------

Re: Really confused about Lenz Law

Only the imaginary lines of magnetic flux looping around the outside
of a magnet will cut across external conductors and create a current
flow in them which will then have its own opposing magnetic field.

see: http://micro.magnet.fsu.edu/electromag/java/lenzlaw/index.html

for a demo.

But you can get around Lenz's law. If you have a single small loop
inside a conductive cylinder or sphere and the distance from the loop
to the outer conductor wall is X and you apply a microwave signal to
the loop such that a 1/4 wave length of the signal equals X then the
normally opposing magnetic field from the current induced in the outer
conductor will be aiding rather than opposing the magnetic field of
the loop by the time it propagates back to the loop.

Lenz's Law only applies at distances much smaller than the wavelength
of the signal involved. The higher you go in frequency, the more time
delay and so the more phase shift across distances between original
signal and counter EMF signals until an opposing signal becomes an
aiding signal.

George
----------------------------------------------------------------------

Regarding your intention on stepping back from tinkering and starting a study on physics and quantum mechanics: while it is very good to learn on topics like that, you actually do learn while tinkering, so why don't you do both at the same time? 

rgds,  Gyula

[void109]

Thanks for the reference.  That's what I was thinking, if the wave length is of appropriate size it should reinforce itself until the core material is saturated.  Does that sound logical? my Internet connection has been down all day or I would have worked on this earlier.  My freq gen and scope only resolve to 50 MHz, so I think I'll have to wrap a rather large core to be able to see and measure it, I think I need 0.5 meter between coils for a 299~ MHz signal.  It will need to be a monster magnetic track, or I just need to get a higher resolution scope.