Impregnation of Toroids for High-Temperature Service

Two materials have been used successfully for vacuum impregnation of magnetic amplifiers and similar devices for continuous operation at 325°F or higher. Complete impregnation, even through layers of interwinding tape, has been achieved. One material is an undiluted silicone rubber capable of withstanding 500°F continuously. The other is a rigid, filled epoxy resin using a nonvolatile hardner, which will withstand 325°F continuously. With proper design, both materials will withstand high accelerations in vibration between --65°F and their maximum operating tempera- ture.