[Boatanchors] [Milsurplus] OK Smart People: Capacitive VoltageDivider?

[jmfranke]

No, the primary winding and the filament winding are to be connected in 
series with the line voltage across the combined winding. What you are 
wanting to construct is an autotransformer. Basically you are adding the 
turns in the filament winding to those in the primary. The new line voltage 
is taken from across the primary winding. If the new voltage is greater than 
the line voltage, reverse the connections to the filament winding.

John  WA4WDL

--------------------------------------------------
From: "Rob Atkinson" <ranchorobbo at gmail.com>
Sent: Sunday, March 18, 2012 8:47 AM
To: <boatanchors at mailman.qth.net>; <boatanchors at theporch.com>
Subject: Re: [Boatanchors] [Milsurplus] OK Smart People: Capacitive 
VoltageDivider?

> I have a question about using a filament transformer to buck 125 v.
>
> It seems to me if you put your 125 v. across the filament winding on
> the secondary, then the primary (that normally has 120 v. on it) would
> have over 1000 v. sitting there?  Unless I am mistaken I'd take care
> when doing this to wrap the primary lugs with 1 kv electrical tape or
> cover them in some other way.   Or, am I somehow mistaken about this.
>
> 73
>
> Rob
> K5UJ
>
>
>>
>>> I'm resurrecting a National NC-100A.
>>> Sounds beautiful. Nice AM, BCB and SWL rig.
>>> One problem: our blasted 125 Volt AC power lines.
>>> This rig wants 110 volts and 125 is very tough on it.
>>> There is no room to hog-wire in a bucking transformer,
>>> so that's out. Niether can I dedicate a variac to running
>>> this receiver.
>>> I understand one can use capacitors as an
>>> AC voltage divider by placing one in series with
>>> a leg of the transformer primary and one across the
>>> transformer primary.
>>>
>>> How can a dummy who can barely do the math
>>> needed to number book pages determine what
>>> values to use to drop this primary voltage from
>>> 125 to 110? Or even if it will work?
>>> Easy! He askes the dozens of people
>>> smarter than him on the mailing lists.
>>> Ain't that cool? ;-)
>>>
>>> TNX ES 73 DE Dave AB5S
>>>
>>
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