Big Variacs but are they useable?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" <Mddeming-at-aol-dot-com>

Hi All,
I have been looking for some Big Variacs on eBay to control a 5KVA 240 V 
piglet, but I suspect that what it not being said in these ads may make 
these unsuitable for TC work. Knowledgeable input requested.

This one
http://cgi.ebay-dot-com/ws/eBayISAPI.dll?ViewItem&category=4665&item=2525401964&rd=1
Says 220 volts 7.5 KVA. It also says 220/50 which might imply 220 V in and 
50 V out.  The picture is just fuzzy enought for the meter scale to be 
unreadable. Heavi-Duty Electric Corp does not show up in my web search.

The second one
http://cgi.ebay-dot-com/ws/eBayISAPI.dll?ViewItem&category=11806&item=2524988160&rd=1
is rated 0-560V 30A.. But what if it is used on 240 V single phase system?

The last one
http://cgi.ebay-dot-com/ws/eBayISAPI.dll?ViewItem&category=11772&item=2526194124&rd=1
says:
"This Staco 2510-3 Variable Autotransformer / Power Supply appears to be in 
good cosmetic condition. 240 V input 60 Hz 0-280V output, 25 Amps, 12.1 KVA."

But 240V -at- 25A is only 6KVA  Also the meters on the unit only go 0-15 Amp, 
which doesn't make sense unless we are talking 3-phase system.

   Are any of these useable/modifiable? I don't want to spend big bucks for 
a "boat anchor".
Thanks,

Matt D.