On Sun, 12 Aug 2012 11:03:24 +1000, "Phil Allison"
wrote:


"spamtrap1888"

I'm wondering though if a secondary is supposed to deliver say 20
volts with a 120V primary and it's hit with 240 then that secondary
will produce 40 volts out.

** Totally wrong !!!!!

Try it yourself and see what REALLY happens.

I'm confused. I would have thought that, at least for the first
instant, the turns ratio means there would be 40 VAC on the output,
until the primary's turns start shorting together as the enamel
combusts because of heating caused by the excessive input current.

** Nope.

Magnetic saturation is an instantaneous phenomenon.

Well yes, it is a quite rapid action, but does not occur till the
current in the primary is sufficiently high. Saturation does not
occur over the whole input wave, and drops and reverses as the sine
wave input reverses. So during the non saturated period, the input
and output voltages are proportional to turns ratio.

peter