On 12/21/2020 6:36 PM, wrote:
Paul the Pedant wrote:
==================
** 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
From that article:
"Things become far more complicated when the secondary feeds a
rectifier, followed by a large bank of filter capacitors. Worst case
inrush current is still limited by the winding (and other) resistances,
but the capacitor bank appears to be a short circuit at the output of
the transformer. Depending on the size of the capacitors, the apparent
short circuit may last for some time. During this period, the
transformer will be grossly overloaded, but this is of little
consequence. Transformers can withstand huge overloads for a short
period with no damage, and they will normally last (almost) forever even
when subjected to such abuse many times a day."
** Please enjoy eating your carefully hand picked cherries.
And don't choke on the pips .....
Well, these cherries support my argument that the initial
1 second of high current is due to the charging of the first
filter caps.
If you have cherries that can disprove my argument,
please present them.