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Re: 4.5amp Variac good enough?

Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>

Hi Matt,

A 12000volt 30mA transformer can be rated in "VoltAmps" or "VA" which is the
measure used for such things.  You simply multiply the voltage and current.  so
your transformer is:

12000 x 0.030 = 360 VA

Your variac is the same idea so:

120 x 4.5 = 540 VA

So the variac has plenty of room to spare.  You will want about 90uF for a PFC
cap.  However, from the chart below, your tranny would run about 550 VA without
a PFC cap so you would still be close to fine.


You may note that variacs can be run at higher than recomended power too for a
short time as shown in figure "F" below.  A little fan helps a bunch too.


However, it is always best to run things within their ratings if you can...



At 09:14 PM 2/25/2001 -0500, you wrote: 
> Hi,I have a 4.5amp variac and wondered if a PFC capacitor used with a 
> 12kv30ma NST could be fed by the 4.5amp variac? 
> matt