Cast Resin Transformers


Ratings :

  • Ratings 25 KVA to 10,000 KVA. H.V. Voltages :
  • 3.3, 6.6, 11, 22, 33KV. Voltages lower than 3.3kv on request.

L .V. Voltages :

  • 433 V and around. Voltages up to 11KV on request.

Insulation Class :

  • F (90°C T`emp. Rise), Others on request.

Applicable Standards :

  • IS1I171 / IEC 60726

Duty :

  • Distribution & Power Transformers.
  • Rectifier/ Thyristor duty.
  • Induction Furnace Duty.
  • Lighting, Isolation.
  • Generator Excitation.

Advantage of Cast Resin Transformers

  • No Fire Hazard.
  • Near Load Center or even near to load.
  • Low as transformer is near to load. Also cable drop is reduced.
  • Negligible smoke generation.
  • Suitable for indoor use as no fire risk.
  • Can be fitted outdoor in IP 45 enclosure.
  • Suitable for as low as -25° C ambient temperature.

Manufacturing Process

Manufacturing Process Core

Three limb core construction is used. Core sheets conforming to drawings are made from Cold Rolled Grain Oriented (CRGO) Silicon Steel sheets. Individual sheets come duly coated with inorganic insulation. Circular Core cross section is used which is obtained by assembling number of steps of different widths. Number of steps and step widths are optimized to gain maximum advantage. Mitred joints are used between the limb plates & yoke plates. Fibre -glass tape banding hold the core tight and reduce the noise level. Treatment given to the completed core, protects it from atmospheric corrosion.


Both the H.V. and L.V. windings are made from copper conductors. Round wire, rectangular strip or foil is used depending on current to be carried. Layer type or cross over type winding is used depending on current / voltage to be handled. Windings are cast under vacuum.

On the H.V. side, inserts are provided to receive tap changing links. Inter connections between H.V. phases are obtained by links made out of copper tubes with their ends formed into lugs. These links are insulated by means of heat shrinkable tubes.


Protection against Overload/high winding temperature can be provided by Thermistors. ALARM and TRIP are provided, when required, by means of Thermistor or RTD sensors can be provided with 2 set points.