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From: fab@faline.bellcore.com (Fabrizio Grandoni)
Newsgroups: rec.audio,sci.electronics
Subject: Re: Audio equipment on 220V/50Hz
Message-ID: <1561@faline.bellcore.com>
Date: Fri, 20-Nov-87 19:39:40 EST
Article-I.D.: faline.1561
Posted: Fri Nov 20 19:39:40 1987
Date-Received: Mon, 23-Nov-87 04:44:31 EST
References: <4032@watdcsu.waterloo.edu> 8884@utzoo.UUCP <63KEN@ORION>
Lines: 49
Summary: Re: Re: Audio equipment on 220V/50Hz
Xref: mnetor rec.audio:4367 sci.electronics:1787




+From ken@orion.bitnet.UUCP Wed Nov 18 06:02:08 1987
+>From: henry@utzoo.UUCP (Henry Spencer)
+>> The 220V is no problem, I can solve that with a reasonably inexpensive
+>> 500 VA step-down transformer.  However, that'll only get me to 110V/50Hz.
+>> Now, this should be no problem for my integrated amp...
+>
+>Um, beware:  the transformer in the power supply is built for 60 Hz, not 50.
+>My impression is that it will sort of work but may have problems with heat
+>dissipation and inefficiency.  Anybody here who knows more about this?
+     
+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,
+if it gets too hot to leave your hand on (and your not one of these Indian
+yogis), its generally not wise to use it.
     
Sorry, it's quite the opposite: a 60 Hz transformer can have serious
problems (burning out...) at 50 Hz. While Ken's argument is correct,
the strong nonlinearity of the hysteresis [nothing in common with
hysterical :-)] gives raise to another effect, which can be dominant:
the lower frequency requires proportionally higher peak magnetic flux
to cope with the applied voltage; if the transformer was designed to
work near saturation @60 Hz (to spare on magnetic material) the need
for more flux will drive the magnetic core deeply into saturation.
This means that: 1) the area of the hysteresis curve increases; and 
2) the magnetizing current rises easily beyond limits allowed by thw
wire section. Both effects result in overheating the transformer. 
But it's good engineering practice to leave adequate safety margin in
the design, i.e. not to exploit the magnetic material to the limit of
saturation; so normally everything should be OK. Unfortunately the
transformer specs (when available) don't help to get the above
information; so all you can do is: a) buy a transformer from a trusted
manufacturer; b) test it yourself (isn't any place over there where you
can find 50 Hz power?).
As last note, remember that the same arguments apply, of course, both
to the external step-down trasformer and to any transformer 
used _inside_ the device (ampli, etc.); so, the first
time you'll use it @50 Hz, watch the smoke...
                                     __
	Fabrizio Grandoni          _/ /_
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