Staco Variac

["Jason Johnson" <hvjjohnson13-at-xxxxxxxxxxx> (by way of Terry Fritz <twftesla-at-xxxxxxxxxx>)]

Hello,
 
I have a Staco 5021CT variac. It is my prized-possesion, as I got it for 50
bucks and it is the best deal I got on all of my coiling stuff. It is rated for
28 amps 240 volts in 0-280 out, 7.8 Kva. My question is: How much can you use
these things over their rated current? It wouldn't be seeing much more than 40
amps  regularly and this would only be for a short time. I know other people
have had this same type of variac in the past as I have seen them in other
posts, but I really don't want to fry my variac.
 
Jason Johnson