Re: Saturable Core Reactor for control puposes?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "davep by way of Terry Fritz <twftesla-at-qwest-dot-net>" <davep-at-quik-dot-com>

> Does anyone know what a "saturable core reactor" is

	Several of us do.


> and what it is used for?

	Controlling AC current.

> Can it be used to control the power in a TC setup?

	Yes.

> I searched with Google but can't quite grasp the concept.

	Texts help.  Web search is nice for some things.
	This is a concept not commonly covered in basic
	summaries of electrical technique, so explanation
	gets lengthy.

	Normally one thinks of an inductor as having a fixed
	value, with a fixed reactance/impedance.
	If the inductor has an iron (steel) core, the
	inductance (reactance/impedance) can be varied,
	over some range, by willfully driving the core
	into and out of saturation.  (Which begs the
	question: what is saturation: see below).  This
	control is usually (always...) done by an
	added winding energized with variable DC.

	Thus, a relatively low amount of DC power can control
	a larger flow of AC power.  Might think of it
	(ROUGHlY) as a controllable 'resistor'.  For
	MANY applications triacs and SCRs have taken over
	where 'saturable reactors' were used.  For some classes
	of loads, especially 'tricky' ones like Tesla systems,
	they have their place.  Many Tesla systems use variacs
	to do the control.  Designing Saturable reactors is
	a nontrivial exercise.

	Saturation (applied to magnetic cores):
	Its not normally encountered, but a magnetic core
	will only 'hold' a certain amount of flux.  If
	too much flux (caused by too much current) is applied,
	the core is said to 'saturate', stops 'holding'
	the flux and, essentially 'disappears'.  (it doesn't
	really, of course....).  This means that the
	impedance/reactance Drops, drastically.  A side
	effect is that things start to overheat and buzz.
	Normally, an inductor is never (intentionally)
	saturated.  If the saturable reactor (inductor) is
	placed in series with an AC power supply and a load,
	it can vary the current/voltage/power to the load.

	However.
	The inductor CAN be designed to operate in that mode,
	or, rather, moving from normal mode to saturated mode.
	(Basically: it gets overdesigned, in a conventional
	sense).  It also has an added 'control' winding, which
	gets driven by DC.  Relatively small amounts of
	DC can move the impedance/reactance from its normal
	value to something close to zero, smoothly,
	steplessly.

	Might look up 'magnetic amplifier', which is a
	'system' using a saturable reactor to control
	power to a load.

	best
	dwp

...the net of a million lies...
	Vernor Vinge
There are Many Web Sites which Say Many Things.
	-me