RE: PDT (Pig) failure modes

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Dave Hartwick by way of Terry Fritz <twftesla-at-qwest-dot-net>" <ddhartwick-at-earthlink-dot-net>

Malcom,
I did not hear that telltale humming from this PDT. The IZ is 2.7%, if that
is significant.

My variac certainly complained, but not a peep from the xfmr.
Dave




Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<m.j.watts-at-massey.ac.nz>

Hi Dave,

On 23 Sep 2002, at 7:16, Tesla list wrote:

> Original poster: "Dave Hartwick by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <ddhartwick-at-earthlink-dot-net>
>
> Malcom,
> With a turn-to-turn short condition, would you not expect some output,
> whether the short exist
> in the HV or LV windings? This is not to put into doubt your experience
with
> xfmr failure modes.
> Dave

It very much depends on the transformer and how good the coupling is
between the windings. The least tightly coupled transformers exhibit
a notable drop in the Q of their windings and a nmoderate to severe
inductance drop in the shorted winding. Tightly coupled transformers
act as though there is a short across all windings. There may be a
modicum of output but it won't be much and the shorted winding will
cause it to emit a loud hum as the winding attempts to jump out of
the core. It will in all probability blow fuses readily. If your
transformer hums like crazy as you apply power, the latter case
probably applies. All serious power transformers should fall into the
second category as coupling relates closely to regulation under load.

Regards,
Malcolm