Hi Angelo,
.9 is about what you get with a choke input filter.
With a full wave bridge capacitor input the no load voltage will be
1.414 times. I usually use about 1.25 figure for loaded voltage when
figuring supply output voltage. It will of course vary depending on how
good the transformer is. But it gets you in the ball park.
For a doubler I figure around 2.5 times for loaded voltage.
73
Gary K4FMX
Angelo Karabetsos wrote:
> 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@ezwv.com>
> >Reply-To: craxd1@ezwv.com
> >To: amps@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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