[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: transformer theory q



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

Tesla list wrote:

> > > You sure about that?

> >         Its a subtle point.
> >         The straight turns ratio, as others have noted, is a good
> >         teaching tool.  However it oversimplifies some aspects of
> >         real world transformer design.  These aspects, as covered
> >         by others, become significant when 'power' is involved.
 
>         All "power transformers" are designed to minimize the leakage
> reactance, so the turns ratio gives the right answer.  The results are
> exact for an unloaded transformer, and very close for any one operated
> within its ratings.  I happen to have been looking at one of my very old
> college EE texts (ca 1941) yesterday and it seems to me to cover all
> significant aspects of power transformer design.  For a typical
> transformer of those days the "design regulation" was about 5%.  That
> meant that, at rated load, the voltage drop in the internal impedance
> (wire resistance plus leakage reactance) was 5% of the applied voltage.
> Most of the drop is in the leakage reactance, and doesn't represent a
> power loss.  The winding resistance must be kept very low to keep the
> transformer from having excessive heating.
 
>         In looking at a modern text on pulse transformer design (about the
> ultimate in power transformers) the only thing I see different about the
> equivalent circuits given is attention to the distributed winding
> capacitance, which has no effect at all at typical power frequencies.
 
> >         (Historical note:
> >         One of the things Tesla provided/sold to Westinghouse was
> >         the 'know how' to make transformer design more real world...)
 
>         Citations?  Tesla was not "into" power transformer design per se, and
> there was already a lot of practical and theoretical design background
> when he came on the scene.  The real innovator in transformer design was
> Charles Steinmetz of what later became GE.

	Agree on Steinmetz.  As i recall, his methods were much
	more user friendly than Tesla's.

	Tesla Transformers AT THE TIME (say ca 1890) meant what we
	now call an AC power transformer.  I've not got a specific
	cite (wish i did....)  Tesla's name (reportedly) was on
	the name plates, along with Westinghouse Corp.

	(One place to research would be tech histories of Niagara
	power development, another would be Inventions, Researches
	and Writings, another one of Tesla's patent collections.

> > > Seems Bassackwards from "the way we was larned in school".

> >         Certain simplifications take place in some training.
 
>         Examples?  (See above).

	Neglect winding resistance, neglect leakage reactance,
	rarely (if ever) see the magnetizing current, esp the
	first cycle surge mentioned...  These are all 'second
	order' effects, granted, but quite real, and of concern
	when handling KW and MW.

	I'm not sure i understand 'pulse transformers' as 'ultimate
	power transformers'.  One is (typically) optimized for max
	bandwidth and 'fidelity' (if those differ), the other for
	max efficiency at One freq and economical performance.

	best
	dwp