How good is your motor insulation systems

The insulation systems in high voltage motors have evolved through time. There are many machines providing good operating performance. Some care and maintenance will keep them running for years to come. Application of existing machines to inverter duty is to be addressed with caution and awareness. New machine designs are making use of the past experiences, and the continuing evolution will ensure that we will have better reliability and longer life, along with smaller, lower cost machines in the future. Against this background, the authors discuss a number of factors which, if considered further, will lead to long life for both new and older insulation system designs. These factors are: (1) system suitability for application; (2) system design and materials; (3) implementation; and maintenance practice. The authors' intention is to provide the reader with an understanding of insulation systems as related to insulation life and performance.