Paul wrote:
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** The largest part of the " inrush surge " is down to the iron transformer
core *magnetising* and losing nearly all of its inductance at switch own.
Can take 20 cycles of AC power for the core to unmagnetise too.
SMPSs usually surge hard at a switch on too, yours must be an exception.
The iron transformer is magnetizing every cycle, which
would be 60 times a second, for 60Hz AC.
** But not at *switch on * !!!!!!!!!
The phenomenon is called " inrush surge" and is a *whole subject* on its own.
This article from my colleague Rod Elliott may give you a hint.
https://sound-au.com/articles/inrush.htm
..... Phil