Vivekanand
    Transformers

Core
Windings
Insulation, Drying
 & Impregnation
Tanks
Painting
Tests


 

 
 



 Process

 

Core

The Core is constructed from laminations of Cold Rolled Grain Oriented (CRGO) low loss electrical silicon sheet conforming to the latest international standards. Each lamination is coated on both sides with carlite insulation which is unaffected by continuous operation in oil at temperatures normally experienced in service of transformers. The core is with mitred joints to reduce corner iron losses and magnetising current and also is designed to have uniform flux distribution throughout the magnetic circuit.

The core limbs are securely bound and yokes are firmly clamped between the mild steel Channels to reduce vibration and inherent humming noise to a minimum. The top and bottom clamps are secured to each other by means of tie rods which secure clamps and also keep the winding in position during normal operation and under fault conditions. The complete core and clamps are effectively earthed.


 

Windings

The windings are made of paper insulated conductors of high conductivity soft drawn electrolytic copper conforming to latest standards. The Transformers windings are suitably designed to meet the mechanical, thermal and electrical requirements. The windings are wound with adequate bracing and anchoring tapes in order to achieve a strong self-supporting structure. The major and minor insulation of winding is suitably designed to withstand impulse test levels corresponding to voltage class as specified in the Indian Standard. Adequate cooling ducts are provided between layers and turns to ensure that temperature gradient between winding, oil and hot spot temperature is within permissible limits. This ensures that the rate of insulation ageing is minimum and consequently life expectancy increased. L.V. Windings with round conductors are of multilayer crossover type. Interlayer paper insulation and anchoring tapes are provided to give adequate electrical strength to the coils. H.V. Windings with strip conductors are of disc type (Continuous). Radial ducts are provided between the adjacent discs which serve the dual purpose of providing insulation as well as oil circulation. Core Coil Assembly - Coils are assembled on core limbs after removing top yoke laminations. Trapping and phase connections are made with multi layer paper covered conductors. They are suitably supported and separated to ensure that adequate clearance is maintained.



Insulation, Drying & Impregnation

All insulating materials used are with the adequate electrical and mechanical strength conforming to relevant standards. Preshrunk insulating materials are used to minimize shrinkage in service. The core Coil assembly undergoes elaborate shrinkage and drying process under hot dry air till windings are thoroughly dried as determined by meggar insulation tests and then is assembled in the tank and flooded with tested Transformers Oil conforming to IS 335. Finally bushings and other accessories are fitted. Routine tests are carried out after windings are completely soaked in oil and trapped air escapes.

Tanks

Tanks are fabricated from mild steel sheets electrically welded. The tank sides are suitably reinforced with stiffeners wherever required. Suitable guide bars are provided inside the tanks to locate the position and to securely fix the Core Coil Assembly to the tank body and prevent any movement during transportation. A robust under base is provided with rollers unidirectional or bi-directional as required. Tanks and other metal clamping components are pretreated after shot blasting to remove rust and scales and then thoroughly cleaned and a coat of Zinc Chromate primer is applied to external surfaces and heat and oil resistant insulating lacquer varnish to internal surfaces. Additional cooling area is provided by pressed steel electrically welded radiators directly welded type or detachable type depending on the size of the transformer. Isolating shut off valves is provided for detachable radiators.

Painting

After complete assembly two coats of gray weather resisting enamel finishing paint highly resistant to chemicals and oil applied. Special paints like epoxy suitable for chemically polluted and saline atmosphere can be given as per customer's requirement.

Tests

All transformers are subjected to routine tests as per IS 2026. We are fully equipped to carry out all routine tests and type test of temperature rise in our works. Special type tests of impulse and short circuit can be arranged in the Central Power Research Institute, Bangalore.