Originally Posted by s/v Jedi
Unless this is a relay with built-in delay mechanism, I don't believe the delay is enough for building up the magnetic field on the Charles transformer. I used to have an old one and the sound of the inrush surge was very clear and lasted about a second at least I think.
No argument that a transformer specific delay is ideal, as the unique transformer characteristics dictate how long in-rush current
So the generic soft start theory is to clamp the first couple cycles of current (which are exponentially the highest) to an acceptable rate. From that point on, the hope is the in-rush is an acceptable value.
As you know, a 25W resistor isn't going to handle very many seconds of 3kW of in-rush.
FWIW, my 6250va torroid pulls <30a in-rush @240v. Not a problem since I have it on a 50a 240v shore power
. (Yes, I have the primary winding protected to less than 50a)