An evaluation of soak versus vacuum impregnation for magnetic components

Vacuum impregnation of magnetic components is a costly operation, due in large part to the equipment required. In a manufacturing operation where the age and heavy usage of the equipment leads to extensive maintenance problems, the cost becomes even more significant due to downtime, repair cost, and production slowdowns. To the extent that vacuum impregnation can be avoided, these problems will be eased. This paper describes an investigation of an atmospheric pressure soak impregnation in which components are immersed in varnish for a reasonable interval with no vacuum pumping involved. The results of this investigation indicate that for Class 105 (?C) operation, and at voltages up to 240 Vac, soak impregnated components behave virtually identically to vacuum-impregnated components. The only difference observed is a slightly greater temperature rise (on the order of 2 to 3 degrees) for the soak-impregnated components, which would have a negligible effect on component life.