[ARC5] Receiver AC Power Supplies

[hwhall at compuserve.com]

 Something that was bugging me today....Ohmic copper loss increases as the square of the increase in current (power equals I-squared x R). Windings carrying 4amps will dissipate 4 times the heat they did at 2amps. So, wouldn't a transformer rated 25vct 2amps (delivering 50watts output) run even hotter if you used it to obtain 12.5volts at 4amps (still delivering 50watts)? Might spell eventual trouble for the insulation around them, if not for the wire itself.

Wayne
WB4OGM

 

-----Original Message-----
From: DSP3 <jeepp at comcast.net>
To: arc5 <arc5 at mailman.qth.net>
Sent: Fri, Dec 12, 2014 1:35 pm
Subject: Re: [ARC5] Receiver AC Power Supplies



On 12/12/2014 10:28 AM, Robert Eleazer wrote:
> Also, Radio Shack has a 25.2 CT 2.0 Amp Chassis Mount transformer, Model 
273-1512 for $14.49.  The RS stores in my area seem to have them in stock.
>
> By the way, that raises a question.  I think I knew once, but when they say a 
center tapped transformer has 2 amps of output, do they mean that it can provide 
25.2VAC at 2.0 amps, which would be 12.5 VDC at 4 amps if connected for full 
wave rectification?
>
> Wayne
>
Tell you what I was told by Hammond when I was working with them for the 
ART-13 transformer suite.  The word they passed was that the current 
rating would be, in this case 2 amps... period.  That's the total 
current that could be drawn.  I've always thought exactly as you but 
maybe they've changed the way things are rated?   If you use the thing 
in a bridge circuit, the rating is 50%.  It appears that the assumption 
being made is that if its CT'ed, that the expected mode.  I have no 
idea, though, how R/S rates their xformers.  But then, what do I 
know....  If'n it don't sag or smoke.. go with it!

Jeep - K3HVG
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