Effects of gaps in inductors and transformers

[Robert Latest]

Your question practically answers itself.

OK. Leakage inductance is the inductance you measure looking into one
winding of a transformer with the other winding shorted. The shorted
secondary winding (ideally) doesn't allow any flux through it, so the
leakage inducance is associated with the flux that goes through the primary
but not through the secondary.

Naturally any removal of core material would reduce this inductance simply
because any conductor loses inductance when it has less highly permeable
material in its vicinity. But tell me a way of removing material that
doesn't degrade, at the same time, the coupling between primary and
secondary windings. After all, simply removing the core of any transformer
will reduce the inductane of any winding (secondary shorted or not), but
what you're left with may not even qualify as a transformer any more.

So the task is: Come up with a transformer configuration in which material
can be removed from the core so that the leakage inductance goes down while
the coupling between the windings is not degraded. You claim to have a
solution. Let's hear it.

robert

 

[John Larkin]

OK. Leakage inductance is the inductance you measure looking into one
winding of a transformer with the other winding shorted. The shorted
secondary winding (ideally) doesn't allow any flux through it, so the
leakage inducance is associated with the flux that goes through the primary
but not through the secondary.

Naturally any removal of core material would reduce this inductance simply
because any conductor loses inductance when it has less highly permeable
material in its vicinity. But tell me a way of removing material that
doesn't degrade, at the same time, the coupling between primary and
secondary windings. After all, simply removing the core of any transformer
will reduce the inductane of any winding (secondary shorted or not), but
what you're left with may not even qualify as a transformer any more.

So the task is: Come up with a transformer configuration in which material
can be removed from the core so that the leakage inductance goes down while
the coupling between the windings is not degraded. You claim to have a
solution. Let's hear it.

robert

Sure. An e-core with primary wound on the center leg and secondary
wound on the right leg. Only half the primary flux threads the
secondary. But as you gap the left leg, pri-sec coupling increases,
approaching 100% for high-mu stuff.

Simple.

John

 

[John Larkin]

Do us a favor, John. Go outside and get struck by lightning, and
then tell me how little difference there is between that plasma
stroke, and a short.

Sorry, we don't get lightning here.

John

 

[Robert Latest]

Sure. An e-core with primary wound on the center leg and secondary
wound on the right leg. Only half the primary flux threads the
secondary. But as you gap the left leg, pri-sec coupling increases,
approaching 100% for high-mu stuff.

Simple.

Yes. I hadn't thought of shunting flux around the secondary, and then
gapping the shunt.

robert

 

[John Larkin]

I stated it, dumbfuck!

Agreed, except that you stated it wrong.

John

 

[Genome]

OK. Leakage inductance is the inductance you measure looking into one
winding of a transformer with the other winding shorted. The shorted
secondary winding (ideally) doesn't allow any flux through it, so the
leakage inducance is associated with the flux that goes through the
primary
but not through the secondary.

Naturally any removal of core material would reduce this inductance simply
because any conductor loses inductance when it has less highly permeable
material in its vicinity. But tell me a way of removing material that
doesn't degrade, at the same time, the coupling between primary and
secondary windings. After all, simply removing the core of any transformer
will reduce the inductane of any winding (secondary shorted or not), but
what you're left with may not even qualify as a transformer any more.

So the task is: Come up with a transformer configuration in which material
can be removed from the core so that the leakage inductance goes down
while
the coupling between the windings is not degraded. You claim to have a
solution. Let's hear it.

robert

I'm going to be called wrong here but, as I understand it, leakage
inductance arises from energy stored in the field that exists in the space
between the two windings and, idealy, its relative value is unaffected by
the core.

At the moment everyone is talking in terms of uncoupled flux and/or flux
coupling which is something entirely different and relates to mutual
inductance rather than leakage inductance.

DNA

 

[joseph2k]

To you, a simple tester.

If you can show us the engineering method to do better, show it to us all.
Otherwise do not crab the gripes of your repeatedly demonstrated betters at
engineering.

 

[joseph2k]

The term for today is:

MAG AMP.

No, they are not the same thing at all. I have worked with both and know
fron direct experience.

 

[joseph2k]

Wow, great link, thanks!

Isn't it just. Best I could find quickly.

I have the following magamp books:
Nonlinear magnetic control devices, Geyger
Magnetic amplifiers, Storm

My (one and only) mag amp bible is:-

"Self Saturating Magnetic Amplifiers"
by Lynn, Pula, Ringelman, and Timmel.
Published in 1960 by McGraw-Hill.
Lib Congress Card Number = 60-6979.

It is a serious tome, and the authors were apparently
staffers at the Westinghouse Electric Corp, Air Arm
Division, Baltimore. Inventors of "mag amp?".

Looks like I borrowed it from the Decca Radar Research
Laboratories, (in 1967), and forgot to return it.

Amazon has one copy, at $80.

none of these even mention ferro-resonant CVTs.

I don't see why a mag amp book should mention the
ferroresonant CVT. OK, the CVT does have a limb
that saturates, but there is no control winding
and it operates as a passive device.

OK its not an exhaustive list of magamp books, but its gotta be
getting close.

[/QUOTE]

As i once learned it, there is a similarity in the theoretical physics; but
a huge difference in the implementation characteristics. It is not a black
art if you can do the physics; non-linear magnetic PDE is no tyro's task.

BTW Terry, that is a pretty good library, it beats mine and my wish list.

 

[joseph2k]

Prevention of saturation is the main reason, even if there is no DC
component involved.

One can also affect how a switcher pulse is handled.

Once again speaking on knowledge that you do not have. Just quit.

 

[joseph2k]

X drops a LITTLE BIT, you fucking retard (inferred in my post)! Now
observe what I said above about being able to drive it harder to make
up for, and even surpass your petty claim of severe losses.

You are too fucking thick, boy.

Curse words and pointless invective do not answer the question.

 

[joseph2k]

The "recursive loop" remark was about the "question practically
answers itself" comment, having nothing at all to do with the subject
of the discussion. The "eddy current" remark was the closest thing I
could think of trying to be funny about the "practically answers
itself" remark, also not having anything to do with the topic.

You analytical types are too stiff lipped to get humor.

Your "attempt" at humor expressed as derisive insult is _NOT_ funny. It is
a major reason that you are considered by many here (by the content of
their responses to you) to be a damn troll. Homie, Eeyore, and Phil A. are
not examples to follow. Far better to look to John, John, Terry, Robert,
Robert, Jim, Jim, James, and Win for examples.

 

[John Larkin]

Gosh John, you make curious. I gave it some thought and did not find an
example. Please elucidate.

One example is about 4 posts up. I'm sure there are others.

John

 

[joseph2k]

Your question practically answers itself.

John

Gosh John, you make curious. I gave it some thought and did not find an
example. Please elucidate.

 

[joseph2k]

Ever seen the switching frequency of the Class D amp chips
available?

Most are 200kHz to 300kHz.

This being used as the front end for a CAT scanner PS I made in
first proto was why we couldn't use them. That made the ripple spec
fail. That spec was 20mV @ 1500 VDC.

And you could not solve that with judicious use of inductance and
capcitance?

We ended up making an audio amp with a string of IGBTs, and it ran
at 17kHz flawlessly. 11mV ripple and 1Volt regulation at 250Watts at
1500Volts. Beat the competition by a factor of two in both ripple and
voltage regulation.

So you ended up with a sucessful design. That is good.

 

[Jeroen Belleman]

I'm going to be called wrong here but, as I understand it, leakage
inductance arises from energy stored in the field that exists in the space
between the two windings and, idealy, its relative value is unaffected by
the core.

At the moment everyone is talking in terms of uncoupled flux and/or flux
coupling which is something entirely different and relates to mutual
inductance rather than leakage inductance.

Are these really different? Either way, it's flux that's created by one
coil and not seen by another. Either way, you can think of it as an
uncoupled series inductance. Reciprocity holds.

Jeroen Belleman

 

[[email protected]]

BTW, a good reference for transformers, inductors, and other AC devices is:http://www.ibiblio.org/obp/electricCircuits/AC/AC_9.html

I'm not impressed. I don't trust any article on transformers that
doesn't include the transformer equations

V1= L1. dI1/dt + M. d I2/dt

V2= M. dI1/dt + L2. d I2/dt

Modelling a transformer as an "ideal" transformer plus leakage
inductances doesn't give the same insight, and it certainly doesn't
give you the right insight.

Incidentally, M above is less than the geometric mean of L1 and L2 -
the ratio of M to the geometric mean of L1 and L2 is the coupling
coefficient, and can be very close to one for good transformers with
high permeability cores.

 

[joseph2k]

Simply the connector style. Not all pins used thing.


Probably standard line level signals passed over that as a
convenient cable choice.

common sense.

No. Not at all. Standard connectors are standard for a reason, they
reliably intermate and match standard connectors. Using a connector alien
to the purpose is counterproductive. If you produced wall warts that used
N connectors for the output you would fail commercially.

 

[Terry Given]

Tony Williams wrote:



As i once learned it, there is a similarity in the theoretical physics; but
a huge difference in the implementation characteristics. It is not a black
art if you can do the physics; non-linear magnetic PDE is no tyro's task.

BTW Terry, that is a pretty good library, it beats mine and my wish list.

I've been interested (obsessed more like) in magnetics since my early
days as a technician, fixing linear and switching psus and monitors
(most of which STILL use transductors for pincushion correction).

I came across magamps not long after graduating uni, and thought they
were interesting, so I've bought every book I can find (I never found
Tony's book).

The only problem with 800 or so engineering books is they weigh a lot

I could easily lose a couple of hundred without affecting the total
knowledge base; they would be the newer ones. But every time someone
whos opinion I respect mentions a book, I try and get it. If Tony's book
wasnt so darned expensive I'd have bought it already.

Cheers
Terry

Cheers
Terry

 

[MassiveProng]

If you can show us the engineering method to do better, show it to us all.
Otherwise do not crab the gripes of your repeatedly demonstrated betters at
engineering.

The GrouseTard? Bahahahaha!