[Amps] Plate transformer current unknown

[Angelo Karabetsos]

I am unable to calculate anything to do with windings or core due to the 
fact it is in a metal case encapsulated in black epoxy. I discovered this 
after removing the lid. I'll say one thing, it's darn heavy and hard to move 
around without anywhere to grab. The secondary wire gauge looks to be about 
18ga and the dimensions are 11"x9"x10" and has a RCA nameplate. Not too much 
more information I can determine. Now I know what to look for at flea 
markets.
One other question. What should the B+ voltage be after rectification. Lets 
say 3000v secondary through a fullwave bridge rectifier and a bank of ten 
470uf 450v caps? I read somewhere to multiply by 0.9 and that should be a 
good rule of thumb. What I am trying to determine is how to calculate the 
proper transformer for the job and keep voltage drop under load to 
respectable figure. Not an easy task to figure out with surplus parts.

Angelo

>From: "Will Matney" <craxd1 at ezwv.com>
>Reply-To: craxd1 at ezwv.com
>To: amps at contesting.com
>Subject: Re: [Amps] Plate transformer current unknown
>Date: Fri, 29 Apr 2005 11:28:25 -0400
>
>Angelo,
>
>Really you cant tell that way (using the resistance) unless you know the 
mean lenght of turn, how many turns per layer, and how many layers they are 
in the winding. This then would give you how long the wire is and you could 
then use the resistance and the length to determine the wire size. If it's 
possible to use a micrometer or a wire gauge to see what the secondary wire 
size is, then one can find out what its rating is. In amateur service, ICAS 
used anywhere from 700 to 900 circular mils per ampere. CCS uses anyhwere 
from say 1000 to 1200 cir. mil. per amp. If you can find the wire size, go 
look at a wire chart for how many circular mils it has and divide by the 
above numbers to determine its current carrying ability. IE, 10,000 circular 
mils running at 1000 cir mil per amp = 10 amperes.
>
>Best,
>
>Will
>
>
>*********** REPLY SEPARATOR  ***********
>
>On 4/29/05 at 3:01 PM Angelo Karabetsos wrote:
>
> >I would like to find out the current rating of a transformer. 
Primary
> >voltage taps 0v-110v-115v-208v-230v and secondary taps  
3450v-0v-3450v and
> >secondary resistance of 53.5ohms from 0v to 3450v tap and 107ohms 
from
> >3450v
> >to 3450v tap. All measurements done with a simple DMM. The 
commercial
> >amplifier it came out of has a plate current meter with a max 
reading of
> >600ma. How could I find out the CCS or ICAS rating?
> >Cheers Angelo
> >
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