Re: [tesla] Soft transformer turn on without a variac

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Original poster: "Peter Terren by way of Terry Fritz <teslalist-at-qwest-dot-net>" <pterren-at-iinet-dot-net.au>

Hi all
Thanks for everyone's comments. The solutions have varied from triacs
through resistors to valves. I am not inclined to use triacs as they have
blown in the current set-up (as solid state 40A zero crossing relays).
Valves are beyond my expertise. Resistors will diminish the problem but will
still give some transients with mechanical switching. I have however
(finally) located an Australian distributor of  inrush limiters (negative
temp coefficient thermistors) up to 30A with 0.5 ohm cool and 0.01 ohm hot
(65 C) resistance.  Several of these in series would drop surge currents in
a 30A system significantly with only a volt or two drop across each when
running.  Unfortunately I don't see how I can parallel them unless thermally
linked with series resistors or inductors to balance the load. (See
http://international2.farnell-dot-com/Search/search-frame.jhtml enter 606832
into search.).  I suspect that they may work best in an SRSG set-up where
maximum current is relatively stable. I will post my results when it is
running.

Cheers
Peter (Tesla Downunder) http://members.iinet-dot-net.au/~pterren/

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Monday, July 28, 2003 2:58 PM
Subject: Re: [tesla] Soft transformer turn on without a variac


 > Original poster: "Black Moon by way of Terry Fritz <teslalist-at-qwest-dot-net>"
<black_moons-at-hotmail-dot-com>
 > What about a triac soulution? iv been thinking about soft start poweron
 > devices that might be even able to have soft off (no hv surges)
 > If anyone wants to hear more just ask.
 >