[ARC5] What's a Transformer?

[Scott Robinson]

Folks,

Well, inside a modern PC you will find few transformers but many power 
inductors, tiny though they are. Current microprocessors  run on a long 
list of closely regulated voltages, like:

	0.8, 0,9, 1.0, 1.2, 1.5, 1.8, and 2.5

The ones near one volt may consume as much as 100A at times. Most of 
these little switchers run on 12V. Not much uses 5V any more and may run 
at up to 2 MHz.

The inductors are generally square ferrite cup core packages, maybe 3/8" 
square or smaller. Look around the big IC (the processor) and you'll see 
it surrounded by such things and by the regulator ICs and capacitors 
they need.

And, these days you can buy ceramic caps with truly amazing capacitance 
in tiny sizes. They are only useful for bypassing and power supply 
filtering, since the capacitance varies enormously with both voltage and 
temperature. Example: 33 uF 20V is about a 3/16 inch cube. Nice low ESR, 
though.

The main power supply, which is, as you say is generally replaced as a 
unit. does have a power transformer, likely about a 1.5 inch cube. Its 
switching process will probably run between 50 KHz and 100 KHz.

The power transformers that make the final use voltage in a 
multi-channel power amplifier that we just did at Dolby Laboratories can 
carry 2 KW each and are about a 2 inch cube in size.

OTOH, we equipped the lab in which we developed the amplifier with 
several 5 kW line frequency isolation transformers. Each one weighs 
about 100 pounds! I mounted them on small furniture dollies so that 
no-one ever has to lift one.

And yes, the amplifier much prefers 208 or 240V line voltage...

Yours for gret smokeless, sound,

/scott robinson


On 7/2/18 6:15 AM, Robert  Eleazer wrote:
> I previously mentioned my salvaging a big transformer out of a AM/FM 
> stereo receiver. Late yesterday I was walking my dog and ran into a 
> young guy I know, the grandson of my next door neighbor, and told him 
> about my find.
> The kid's  a real wiz at computers and has his own workbench in the 
> garage with electronic parts and a soldering iron.  He is not afraid to 
> take things apart and fix them.  But he responded by saying "What's a 
> transformer?  What's it look like?"
> It turns out that he had also salvaged a home video receiver system, one 
> with a 700W max output, and got an even bigger transformer out of it but 
> did not know what it was. Aside from the many IC's he only recognized 
> the big electrolytic capacitors.  He brought me the remains of the 
> device last night.
> It never occurred to me that someone who did so much with computers 
> would not know what a transformer was.  But inside a PC you really don't 
> encounter them.  Power supply repair there consists of swapping out the 
> whole thing with a known good one.  I think I'm going to have a little 
> educational session with him.
> Wayne
> WB5WSV
> 
> <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient> 
> 	Virus-free. www.avg.com 
> <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient> 
> 
> 
> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
> 
> 
> ______________________________________________________________
> ARC5 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/arc5
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:ARC5 at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>