Ferrites: L changes with current change.

I have a couple of old (discrete transistor) power supplies that use a form of mag amp to control the voltage output from the main transformer so as to reduce the series transistor dissipation.

Mag amps are _cool_. Slow, bulky, and heavy, but bulletproof and highly effective.

Cheers

Phil Hobbs

They're not as outdated as you'd think. Ponder this: all ATX power supplies use a power transformer with 5 and 12V windings. Where does the 3.3 come from?

Hint: the series inductor that "filters" the 3.3V supply is wound on a metglas toroid!

Tim

-- Deep Friar: a very philos>

Until the Supreme Court decision, Florida certainly thought so ;-)

-- "Electricity is of two kinds, positive and negative. The difference is, I presume, that one comes a little more expensive, but is more durable; the other is a cheaper thing, but the moths get into it." (Stephen Leacock)

Graham where did you go, To quote you "Either you KNOW or DON'T KNOW !" Three days, no response, does that mean you don't KNOW? Mike

Not much space for them left in today's technology. But its sad to see how many people have forgotten about (or never learned) the principles behind this kind of stuff.

I can understand colleges not bothering with mag amps and toobs and TWTs and what-not in the regular circuits classes anymore, but it sure seems like there should be an elective in bigger colleges for a class on "all the technology you've never heard of...but might just want to know about for certain specialized applications..."

OK, maybe a book on the topic would be more like it... there are certainly plenty of books on these older technologies, although nothing that tries to group them all together in one...

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hly

Yup, I'd never heard of them. The wiki article was not much help. Do you have any good references?

George H.

I have a copy of,

Paul Mali, _Magnetic Amplifiers / Principles and Applications_, John F. Rider Publisher, Inc. (1960).

It shows operation and use well enough that you could put one together, but it's not a nuts-and-bolts thing where you can design a mag amp from B-H curves and circuit values and such. If you can find a copy (library or online?), it's a worthwhile introduction.

Tim

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Nothing good specific to mag amps. But they do get some coverage in many of the older handbooks I've run across.

-- "Electricity is of two kinds, positive and negative. The difference is, I presume, that one comes a little more expensive, but is more durable; the other is a cheaper thing, but the moths get into it." (Stephen Leacock)

On a sunny day (Wed, 30 Dec 2009 07:32:11 -0800) it happened Fred Abse wrote in :

Nice.