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From: ruck@sphere.UUCP (John R Ruckstuhl Jr)
Newsgroups: sci.electronics
Subject: Re: X-formers saturation
Message-ID: <197@sphere.UUCP>
Date: 18 Mar 90 05:48:26 GMT
References: <2437@ultb.isc.rit.edu> <2439@milton.acs.washington.edu>
Distribution: usa
Organization: Private; Colorado Springs, CO
Lines: 24

In article <2439@milton.acs.washington.edu>, whit@milton.acs.washington.edu (John Whitmore) writes:
> In article <2437@ultb.isc.rit.edu> deb5584@ultb.isc.rit.edu (D.E. Baker ) writes:
> >
> >	Can someone tell me what happens when a transformer saturates ?
> >Is it the primary,secondary,core...?  How do you tell when this happens?
> >
> 	If you hear a transformer buzzing (generating acoustic
> energy far from 60 Hz), saturation and the associated distortion
> of the 60 Hz waveform should be suspected.  If the lights in

I believe transformers operated at 60 Hz normally hum at 120 Hz.  Iron 
core expansion (shrinkage?) is a function of !magnitude! of the magnetic
flux density in the core.  Flux (or flux density) is a function of the 
exciting current, i.e. it cycles at 60 Hz, but the !magnitude! is
periodic at 120 Hz.  Because this function (magnitude) is not sinusoidal 
(when the exciting current is sinusoidal), and because of core 
hysteresis (sp?) and any other nonlinearities, the 120 Hz hum is rich
with harmonics.  Saturating the core, i.e. operating the transformer at
levels where the EMF/flux relationship is nonlinear, would introduce
added distortion, but I do not believe my sense of hearing is sensitive 
enough to distinguish such a change of acoustic energy in the harmonics
of the 120 Hz audio signal.
-- 
John R Ruckstuhl, Jr	...!hplabs!hp-lsd!sphere!ruck