[Johnson] Need tech advice on xfmr

[Darrell, WA5VGO]

I've got to go along with you, David. I would also add that the 90 mA 
rating is probably for a choke input filter. It would need to be de-rated 
for a capacitor input filter. Also, although I doubt it would be an issue 
at this relatively low voltage, many transformers with a center tap to not 
have sufficient insulation to allow it float above ground in a bridge circuit.

73,
Darrell, WA5VGO


At 07:36 AM 11/27/2005 -0500, David C. Hallam wrote:
>Ed,
>
>Unless some of the transformer guys weigh in and show me that I am wrong, I
>will stick by my contention that the transformer is rated for approximately
>25 watts in CONTINUOUS duty service with the center tap grounded.  I will
>agree that for intermittent duty service with a light bleeder load, you can
>get for than 25 watts out of it.  Leaving the center tap above ground does
>not increase the power rating of a transformer.
>
>-----Original Message-----
>From: Ed Tanton [mailto:n4xy at earthlink.net]
>Sent: Saturday, November 26, 2005 9:52 PM
>To: dhallam at rapidsys.com; C E; johnson at mailman.qth.net
>Subject: RE: [Johnson] Need tech advice on xfmr
>
>
>Not correct: IF the transformer is indeed rated for 520VAC at 90mA,
>then (regardless of the CT) it is capable of ~ 46W. Period.
>
>At 01:24 PM 2005-11-26, David C. Hallam wrote:
> >The answer is maybe.
> >
> >The transformer rating is approximately 520/2 x .090 = 23.4 watts.
> >Depending upon the size of wire used to wind the transformer you could
> >probably get 120 mA at 260 VDC out of it.  Breadboard the rectifier circuit
> >and let it run for awhile and see how hot the transformer gets.  If it gets
> >too hot to touch, the answer is no it won't work.
> >
> >No, it is not rated for 180 mA in a FWB.
> >
> >73
> >David
> >KC2JD
> >
> >-----Original Message-----
> >From: johnson-bounces at mailman.qth.net
> >[mailto:johnson-bounces at mailman.qth.net]On Behalf Of C E
> >Sent: Saturday, November 26, 2005 1:05 PM
> >To: johnson at mailman.qth.net
> >Subject: [Johnson] Need tech advice on xfmr
> >
> >
> >Speaking of xfmrs, I would like to know (say, a
> >replacement xfmr for an EFJ transmitter) is rated at
> >520 VCT at 90 mA and I would like to use it in another
> >application that requires 260 VDC at 120 mA, would
> >this transformer work without getting fried? Does the
> >90 mA mean 180 mA in full bridge configuration?
> >Thanks. Cal.
> >
> >
> >
> >__________________________________
> >Start your day with Yahoo! - Make it your home page!
> >http://www.yahoo.com/r/hs
> >Johnson mailing list
> >Home: http://mailman.qth.net/mailman/listinfo/johnson
> >Help: http://mailman.qth.net/mmfaq.html
> >Post: mailto:Johnson at mailman.qth.net
> >
> >
> >Johnson mailing list
> >Home: http://mailman.qth.net/mailman/listinfo/johnson
> >Help: http://mailman.qth.net/mmfaq.html
> >Post: mailto:Johnson at mailman.qth.net
>
>Ed Tanton
>
>website: http://www.n4xy.com
>
>All emails <IN> & <OUT> checked by
>Norton AntiVirus with AutoProtect
>
>--------------------------------------------------
>"Right is right, even if everyone is
>against it; and wrong is wrong, even
>if everyone is for it."
>
>William Penn
>--------------------------------------------------
>
>
>
>
>Johnson mailing list
>Home: http://mailman.qth.net/mailman/listinfo/johnson
>Help: http://mailman.qth.net/mmfaq.html
>Post: mailto:Johnson at mailman.qth.net