Re: SOLA Constant Voltage Transformer


"isw" <isw@xxxxxxxxxxx> wrote in message
news:isw-8CCD33.22483710012007@xxxxxxxxxxxxxxxxxxxxxxxxx
In article <1168487645.556391.135450@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
"dre" <dre7@xxxxxxxxxxxxx> wrote:

Hi:

New poster here, just wondering if anyuone can help me with this beast.
I'm sort of hoping to use it as an isolation transformer for my
scanner. Overkill, I know, but it cost me all of 15 bucks. The
problem is the voltage it produces on the secondary is 132 volts with
line voltage in. The plate states secondary voltage is 118, so what's
causing the overage? Do I not have it loaded enough (rating, IIRC is
2.5 A) or could it be the capacitor failing? Any advice is
appreciated.

Most constant-voltage transformers output a semi-square wave (sort of a
sinusoid with the tops flattened). It will not measure "properly" with
most voltmeters.

Isaac

I don't understand why a ferroresonant transformer / capacitor combination,
should output anything other than a sine wave. Many years ago, I worked for
a company which made use of these devices to feed radio relay equipment, and
as far as I recall, they just had a normal sinewave output. I had a quick
look on the 'net at some Sola ones, and there is nothing in the specs to
suggest other than a sinewave output. It does, however, state that the
output voltage can be have a variance of +10 to -20% of the nominal rating
plate value. For the OP's example, that is potentially nearly 12v high worst
case, which added to the 118, gets pretty damn close to the 130 odd that he
is measuring. I wouldn't have expected his scanner to be that fussed about
this sort of level of overvolts anyway. Depends to some extent on the type
of power supply it uses. Also, as someone else suggested, loading the CVT
will probably bring the voltage down a little, although it wouldn't be a
very good CV source, if it dropped too far ...

Arfa


.

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