[ARC5] Receiver AC Power Supplies

[Mike Feher]

Exactly - I just used fewer words, HI. 73 - Mike 

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 


-----Original Message-----
From: ARC5 [mailto:arc5-bounces at mailman.qth.net] On Behalf Of Dennis
Monticelli
Sent: Friday, December 12, 2014 10:38 PM
To: Mike Feher
Cc: Wayne Hall; ARC-5 Maillist
Subject: Re: [ARC5] Receiver AC Power Supplies

The most transformer friendly rectifier circuit is the full wave bridge
because the entire winding and flux paths are used for each half of the
waveform.  The full wave center tap is not as good but it's pretty good.
Transformers are optimized for a balance of wire loss and core loss while
avoiding saturation.  The rectifier circuit used affects the optimization.
So if a different circuit is used than recommended you usually cannot
achieve the the full VA rating.  Having said that you won't fall that short
with a different rectifier circuit unless it's a half-wave circuit because
those are very transformer unfriendly (you're only using half the
transformer).

Dennis AE6C

On Fri, Dec 12, 2014 at 6:39 PM, Mike Feher <n4fs at eozinc.com> wrote:
>
> It has been a long time, but, could it have to do with core 
> saturation? 73
> -
> Mike
>
> Mike B. Feher, N4FS
> 89 Arnold Blvd.
> Howell, NJ, 07731
> 732-886-5960
>
> -----Original Message-----
> From: ARC5 [mailto:arc5-bounces at mailman.qth.net] On Behalf Of 
> hwhall at compuserve.com
> Sent: Friday, December 12, 2014 9:31 PM
> To: jeepp at comcast.net; arc5 at mailman.qth.net
> Subject: Re: [ARC5] Receiver AC Power Supplies
>
>
>  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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