Cast-resin transformers are dry-type transformers which the magnetic circuit and windings are not immersed in an insulating liquid but are cast with an epoxy resin mixture. These special transformers are finding an ever-increasing scope of application for their high-service reliability.

Cast-resin transformers are a popular choice for use in commercial, industrial and residential sites. These power tranformers require practically no maintenance and have a much lower environmental impact than traditional oil-immersed transformers. Auto-extinguishing and other safety features make it the obvious choice for indoor applications and other areas with high fire risk.

Casting Process

The casting process minimises the deposit of pollution and corrosive particles as well as being strong and waterproof. The active parts are cast with a resin mixture of quartz flour and epoxy resin after being secured to a mould and preheated under vacuum.

Cast resin transformers are characterized by the conductors of the HV winding being embedded completely in an enclosed cast resin body with a smooth surface. Even if not specified so explicitly by the standard, this can be achieved in production of high voltage applications only using vacuum-encapsulated moulds.