In article
s.com, Matty F scribeth thus
On Mar 14, 1:41 am, tony sayer wrote:
Here's a 33kV audio transformer and a couple of current transformers.

33 kV!.. Whatever was that for electrostatic speakers or an AM
transmitter?...

http://i43.tinypic.com/osfh95.jpg

The audio transformer was used for telephone wires that ran around the
country underneath 33kV powerlines using the same pylons. Every now
and then the 33kV wires would fall down on to the telephone line and
the telephone girls used to complain about their telephones exploding.
There were circuit breakers and fuses but those took too long to
operate. The transformer was required to withstand 33kV between
primary and secondary for up to a minute, as well as passing 30,000 Hz
plus 17 Hz ringing frquency.

Right!.. This surely wasn't in the UK?. I know they sling wires on low
voltage 230/415 lines but can't say I've ever seen them on anything
higher volts...

This it did very well. I've always though there must be a use for such
a transformer these days. It could pass up to 100,000 Hz without too
much loss. It was rated at 100 watts. The production version had a
toroidal core of grain-oriented silicon steel. I am the only person
alive who knows why it works at such a high frequency, and the special
insulation that was successful after many prototypes failed. The
picture is of prototype 1, of 12.


--
Tony Sayer