Inrush and prevention? was Re: power supplies form those 24v transformers

Hi,
I had trouble with inrush also on the power supply for my mill. It
has 3 large transformers and an auto-transformer I wound to drop the
supply voltage. The inrush caused minor welding at the plug. I
played with placing a 300w-500w halogen bulb in series with the
primary, then a relay would short across it after a few seconds. The
halogen bulb has its own inrush, but its minimal compared to that of
the transformers. On power-on you could just barely see the element
light up for a fraction of a second.

This worked well, but I later just went with a hefty 20amp NTC that
I got as a free sample. They have a cool-down time constant to
return to the 'higher' resistance state, which means you have to
wait about a minute between power cycling, or design in a time
delayed relay to short across the NTC after intial power on, then it
can cool down for the next time.
-Lee