[sdiy] Re: No Variac Warning!

[Ken Stone]

There was one amusing situation at the place I used to work, where a Variac
proved to be a problem. The unit under test was power conditioner that used
triacs to switch between different taps on the primary of the transform to
keep the output on the secondary relatively constant. One triac shorted
(effectively producing an autotranformer with respect to the other triacs),
so the technician wound the Variac down to zero instead of just hitting the
power switch. The result was it blew every triac in the thing as each was
switched into the circuit in turn!

>>I wouldn't advise using a Variac with anything using a transformer!!
>>(Variac to transformer = Heap Bad Mojo)!
>>Seriously folks
>>The windings of many a transformer are simply not designed for
>>anything other than a standard mains supply from the wall.
>
>This is not correct. So long as the transformer is fed the proper
>FREQUENCY, in a clean sine wave, it can be fed any AC voltage
>from zero up to its rated input. Service technicians routinely
>use variacs to power-up equipment slowly after repair--even
>items with switching power supplies. And fixing old tube equipment
>absolutely demands the use of a variac, to re-form electrolytics.
>
>
>
>
>E. Barbour
>metasonix
>
>
_______________________________________________________________________
Ken Stone   sasami at hotkey.net.au  
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>