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From: email@example.com (Nico Coesel)
Subject: Re: Doubling wallwart power rating
Date: Mon, 07 Oct 2002 14:08:55 GMT
NNTP-Posting-Date: Mon, 7 Oct 2002 14:10:49 +0000 (UTC)
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firstname.lastname@example.org (Gibbo) wrote:
>John Woodgate email@example.com wrote:
>>I read in sci.electronics.design that Gibbo
>>wrote (in <firstname.lastname@example.org>) about 'Doubling
>>wallwart power rating', on Mon, 7 Oct 2002:
>>>Can you explain the relationship between higher current and core saturation
>>The voltage available to produce the induction in the core (equal and
>>opposite to the back-e.m.f, which may clarify the matter) is equal to
>>the supply voltage minus the voltage drop across the winding resistance.
>>A higher output current implies a higher input current, therefore more
>>voltage drop, therefore less induction.
>>Someone in this thread said that there is a compensation effect - less
>>induction implies less magnetizing current. So, over a range of output
>>currents, the input current magnitude may be nearly constant (but the
>>phase varies). Except for a very small transformer indeed, (e.g. 1 VA),
>>the magnetizing current is much less than the total input current at
>>rated load, so the constant-current range is likely to occur under some
>>rather light load conditions.
>Thanks but what I actually wanted to hear was the other posters response to the
>question. He stated that increased current draw will saturate the transformer.
>I was most interested to hear how :)
I assumed that similar problems arise like in SMPS where the current
in a given inductor is limited by core saturation.
Reply to nico@nctdevpuntnl (punt=.)
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