Re: Question about magnetic forces beyond saturation

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"Salmon Egg" <SalmonEgg@xxxxxxxxxxxxx> wrote in message news:SalmonEgg-BC0F77.18210530092009@xxxxxxxxxxxxxxxxxxxxxx
In article <q_Swm.216430$sC1.204957@xxxxxxxxxxxx>,
"Don Kelly" <dhky@xxxxxxxxxxxx> wrote:

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"Salmon Egg" <SalmonEgg@xxxxxxxxxxxxx> wrote in message
news:SalmonEgg-9A378A.18465029092009@xxxxxxxxxxxxxxxxxxxxxx
<snip>
> I am not certain if I understand the configuration. Without worrying
> about how to wind the coils,I think you mean that you take two of what > I
> will call "O" cores. You cut a piece out of one so that it slips over
> the intact core. If that is the case, the induced voltage is zero. If
> nonlinearity is present like from saturation, you have the makings of
> what is called a paraformer.

You have the configuration and the answer right. The core material is ideal
so saturation is not a factor.

The paraformer is an interesting device, by saturating a common core
section for the configuration described above, the exciting winding
drives the common core into saturation at double the exciting frequency.
Therefore, you have an inductor with a periodically changing inductance.
This can be the basis for a parametric oscillator. One advantage is that
the oscillator stops working when overloaded or shorted.


>>
>> Another oldie, circuit related, is the evaluation of the resistance
>> between any two vertices of a pentagon with 1 ohm resistors between >> each
>> vertex and all of the other vertices (i.e. 4 leads per vertex) . I
>> expect
>> that most have run across this one.
>
> I have not run across it. I will get back to it later because my mind > is
> not functioning all that well right now. But from what I see, I have a
> plan of attack.
>
> There are two cases. One is to measure resistance from adjacent
> vertices. The other is when a vertex is skipped. I can see that as I
> start making resistor connections, there will be a number of points > with
> the same voltage. When a resistor such points, no current will flow so
> that that connection might just as well be left open. Another way of
> looking at it is that you start to form balanced bridges.
>
> I will have more to say on that later.

The next variation is any polygon with the vertices so joined, or a cube in
which each vertex is connected to every other vertex through a 1 ohm
resistor (7 leads per vertex). Following that is the resistance between
adjacent nodes of an infinite rectangular grid of 1 ohm resistors. All cute
and useless but easily solved.

For now, I will pass on solving such problems. I will only point out
that those properties have some interesting applications. In telephone
(and telegraph if you remember that) technology, hybrid coils are used
to allow full duplex operation on a single pair of wires. Some
connections are made using the bridge principle so as not to excite some
circuit elements but not others. Examples are: When you talk on an old
POTS phone, you do not blast your ear. Similarly, Amateur radio phone
patch traffic with automatic voice control was possible because the
hybrid coil allowed speaker output to go onto the telephone line without
getting to the transmitter microphone input. Talking signals on the
telephone get to the transmitter microphone input whether local or
remote.

Bill
Bill

--
Private Profit; Public Poop! Avoid collateral windfall!

Thanks a lot.

I can see the paratransformer situation but as this problem was first introduced to students in an introductory magnetic circuit machines course as a test question (and ideal core conditions assumed so saturation and variable inductance of the core material was not a consideration) -it was useful in sorting out thinkers from formula pluggers. Once the effect of saturation in part of the secondary loop was considered-- another, and messier, problem. No answers considered this (and data was not available to allow a definite numerical answer).
I do admit that circumstances moved me away from communications toward power systems and machines so I am not familiar with telephone or ham radio practice.
--
Don Kelly
dhky@xxxxxxxxxxxx
cross out to reply

.

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