Cast Resin Dry Type Transformer (CRT)

Cast resin dry type transformers are used for indoor as well as outdoor applications. In these transformers, the complete encapsulation of primary and secondary winding in epoxy resin prevents penetration of moisture into windings. The cast resin offers very good protection against adverse ambient conditions. These transformers can work without disruption of service at 100% humidity. Due to the high grade insulation material, coils are non-hygroscopic & the transformer can be switched on directly without pre-drying even after a long period of service interruption. Contrary to the conventional dry type transformers the cast coil transformers are better in respect of impulse voltage withstand strength.

Higher dynamic short circuit withstands strength as compared to oil immersed and conventional dry type transformers because of fibre glass reinforced epoxy encapsulation. No partial discharges can occur during operation. The insulation material used is glass fibre reinforced with epoxy resin of class ‘F’ which can withstand wide temperature variation. Class ‘F’ insulating polyester resin can withstand hot spot temperature rise upto 145 Degrees Celsius and maximum winding temperature upto 180 Degrees Celsius. Due to high quality insulation material the transformer is practically non-inflammable by an electrical arc. Hence special fire protection measures are not required.

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