RE: Soft transformer turn on without a variac

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

Original poster: Thomas <tom-at-pwrcom-dot-com.au> 

 > Original poster: "Robert Jones" <alwynj48-at-earthlink-dot-net>
 >
 >  > Original poster: "Crow Leader" <tesla-at-lists.symmetric-dot-net>
 >  >
 >  > I found this fun link about transformers and inrush current:
 >  >
 >  > http://www.allaboutcircuits-dot-com/vol_2/chpt_9/12.html
 >  >
 >  > which supports Gary. It turns out my solid state relays are "zero
 > crossing"
 >  > on the spec sheet, not phase (like I though) control so
 > that screws up my
 >  > project. It does seem interesting you don't see any solid
 > state relays
 > that
 >  > are 90 degrees off zero crossing or maybe "full voltage
 > crossing"  for
 >  > transformers, or are there any?
 >
 >
 > Try this link http://relays.tycoelectronics-dot-com/app_pdfs/13c3206.pdf
 >
 > It explains the transient x2 thing and with saturation the x2
 > and beyond
 > thing.  Its also mentions residual magnitisim which may
 > perpetuate the view
 > that that has something to do with the surge.  In fact normal
 > transformer
 > materials are selected to have low hysterisis ie the residual
 > flux is low
 > compared with the induced flux hence the effects of residual
 > flux on the
 > size of the surge will be small compared to the surge size without
 > saturation.
 >
 >
 > Bob
 >

Ok, in light of information from the above links, I retract my suggestion to
use a zero crossing switch.

It seemed like a good idea at the time (reasoning was 0 volts = zero amps at
start up). Sorry for the misinformation.

I had the zero crossing switch links on hand because I was planning on using
one to power up the variac in the test room at work (it keeps tripping
breakers), now however I shall use the switched resistance idea.

Thanks,

Tom.