SECOND HAND 
nht-4000w thyrister electric volatage regulater 
TESTED WORKING.
Variable volatage AC supply, needing 20w minimum load to work.
It provides a variable output AC voltage from 0v to 220v ac.
Maximum power = 4kw resistive load or 1/3 if this for an inductive load.
= 1.3kw (1,300 watts)