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From: dmt@ptsfa.UUCP
Newsgroups: rec.audio,sci.electronics
Subject: Re: Audio equipment on 220V/50Hz
Message-ID: <3795@ptsfa.UUCP>
Date: Thu, 19-Nov-87 14:12:00 EST
Article-I.D.: ptsfa.3795
Posted: Thu Nov 19 14:12:00 1987
Date-Received: Sat, 21-Nov-87 16:38:32 EST
References: <4032@watdcsu.waterloo.edu> <8884@utzoo.UUCP> <63KEN@ORION>
Reply-To: dmt@ptsfa.UUCP (Dave Turner)
Organization: Pacific * Bell, San Ramon, CA
Lines: 27
Xref: utgpu rec.audio:3613 sci.electronics:1542

In article <63KEN@ORION> KEN@ORION.BITNET (Kenneth Ng) writes:
>     
>Using a 60 Hz transformer at 50 Hz will probably be ok, the opposite might
>not.  Heat generated by the transformer is a function of the 'area' of
>the hysterious curve multiplied by the frequency.  Therefore the lower
>the frequency the lower the heat production.  But, just to be sure,

I thought it was just the opposite: it is ok to use a 50 Hz transformer at
60 Hz but not the reverse.

A low frequency transformer requires more iron than a high frequency one.
That's one reason they started using 400 Hz in aircraft.

The current in any inductor is limited by the inductive reactance.
Lowering the frequency will lower the inductive reactance and increase the
current and the amount of heat produced. Lowering the frequency to the
extreme 0 Hz (DC) is generally not recommended for any transformer.
The DC resistance of the windings is low and the current will be very high.
Increasing the frequency will have the opposite effect. The inductive
reactance will be higher and the current lower.

Heating is due (in part) to I^2R losses, IR (eddy currents), and hysteresis
losses. Eddy current and hysteresis losses increase rapidly with frequency
but ordinary iron cores are good up to about 15,000 Hz.

-- 
Dave Turner	415/542-1299	{ihnp4,lll-crg,qantel,pyramid}!ptsfa!dmt