Path: utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!zephyr.ens.tek.com!tekig5!brianr
From: brianr@tekig5.PEN.TEK.COM (Brian Rhodefer)
Newsgroups: sci.electronics
Subject: Re: 100V Japanese products on 120V US lines
Keywords: transformers
Message-ID: <5288@tekig5.PEN.TEK.COM>
Date: 2 Jan 90 19:27:55 GMT
References: <3215@uceng.UC.EDU> <1201@ariel.unm.edu> <25539@cup.portal.com>
Reply-To: brianr@tekig5.PEN.TEK.COM (Brian Rhodefer)
Distribution: na
Organization: Tektronix, Inc., Beaverton,  OR.
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In article <25539@cup.portal.com> tekig5!zephyr.ens.tek.com!uunet!portal!cup.portal.com!dbell dbell@cup.portal.com (David J Bell) writes:
>
>Only a small quibble: the *primary* current is what you have to worry about,
>not the secondary: since all the load current flows through both transformer
>windings, they get equal current, unlike the usual case where the primary is
>low current and the (step-down) secondary is much higher. You'd want to first
>find out what the primary current rating *is* before selecting the transformer
>to use. To wit: 
>

Dave is greviously mistaken.  The original poster was quite correct:
the load current determines the transformer's secondary current rating.
The same current most emphatically does NOT flow through both the primary
and the secondary, as anyone who purports to understand transformers ought
to know.  Suggesting that the primary and secondary currents of an operating
(not saturated, etc) transformer are equal is the same as suggesting that
the winding voltages are equal, and I doubt even Dave believes that.
 (note: excitation currents neglected.)

Brian Rhodefer