15 May
2007
15 May
'07
12:27 a.m.
Anytime you use a variac, it is wise to put a current limiter in series.
This can be done easily with an incandescent bulb (about 60W or 75W).
This prevents any surge entering the circuit if there is a short. The
surge in power cause the lamp to glow very bright which creates high
resistance thus reducing the current. When a unit is functioning
properly without any shorts at nominal voltage, the bulb will just have
a faint dim.This is the oldest trick in the book.
=Dan
[ My Corner of Cyberspace http://ragooman.home.comcast.net/ ]
Chuck Guzis wrote:
Would it perhaps be better to insert a series
resistance with the
mains supply rather than a variac? This would allow full line
voltage to be present at the input of the PSU, yet provide a bit of
protection should something start to draw a too-large amount of
current.
I'll usually insert an appropriately-sized incandescent lamp in
series with the line when I'm powering up an older piece of equipment
in unknown condition.
Cheers,
Chuck