Permalex® II insulation system

The insulation system known as Permalex I and used in distribution transformers has served the industry very well since its introduction in 1959. However, new requirements, applications, and the ever changing needs of the industry have created a threefold incentive to improve the system. The first is the desire of some distribution transformer users to increase the permissible overload which can result in higher coil hot spot temperatures. Second, the new and rapidly expanding market for underground application has meant in some instances higher operating temperatures because of less efficient cooling than for the conventional pole type. And last, the continual industry goal for reducing transformer size and cost as might be accomplished by an insulation system which can operate at higher temperatures without additional sacrifice of life or operating characteristics.