The Vacuum Pressure Impregnated Dry Type Transformer are vacuum pressure impregnated with a high temperature polyester varnish. VPI ventilated dry type transformers are designed to meet most commercial and industrial applications. VPI transformers provide excellent mechanical and short circuit strength, no danger of fire or explosion, and no liquids to leak.This technique applies the varnish coating in interchanging cycles of pressure and vacuum. The VPI process uses polyester resin. The coils are then cured in an oven. The VPI process is better than the standard dry-type transformer because it includes pressure in addition to vacuum. This process allows better penetration of the varnish in the transformer coil. These units offer an increased resistance to corona.
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