Core Coil Assembly
It is always ensured that all the HT & LT coils are preshrunk, varnished and dried before assembly. Special care is taken to make the core coil assembly mechanically and electrically strong. For this, vertical and horizontal supports of PC Board of required strength & size, suitably interlocked, are provided. Each HT coil section is separated by press board rings. Yoke insulations are made of PC Board, permalli wood or Bakelite sheets, depending upon the size and voltage class of the transformer. LT leads are taken to the bushing terminals through proper bus bars/flexible jumpers. HT tapping leads & line leads are taken to the respective terminals through SRBP tubes-all suitability braced. Complete assembly is then dried in thermostatically controlled oven at 90 C. At the end of the drying cycle, the core assembly is further tightened to take care of the shrinkage.
Insulation & Oil
All insulating systems are carefully selected with due consideration given to electrical, mechanical & thermal properties of insulation. The oil is used as a coolant and insulating medium. It is tested for di-electric strength as per IS:335, before topping up. Second filtration is carried out just before despatch.