Open type ballast for 40W. & 20W. FTL was introduced during early nineties in India. A base plate, coil, "U" & "T" type of lamination with Aluminium air gap material, nylon end caps and terminal are the parts going this product. Air gap thickness could be reduced to get the required current by compressing air gap material/wire, this is called calibration. This takes care of variation of wire and lamination quality. There are other type of lamination to get the same effect like odd legged E & I, M & I etc. where calibration are possible.
There are other types of open type ballast (Chock) with fix air gap where calibration is not possible like some ATCO ballast where double - C & I Lamination is used for the magnetic core. Our SPM is specially designed with latest technology to improve the power consumption/reducing calibrating the ballast with hydro pneumatic pressure before crimping the base plate. We have supplied to most & major manufacturers and are used for CFL, PL & FTL, ballast 5 to 58 w. & 70w to 400w. HID.