Class H insulation system for rotating equipment

In light of modern application trends, with variable speed drives and permanent magnet technologies, the use of Class H (180 degC) insulation systems is a necessary step to utilize these new technologies to their fullest capabilities. Present high voltage (HV) insulation systems utilize well-known global vacuum pressure impregnation (VPI) methods that have been in place since the 1960s. These systems have been rated Class F (155 degC) and in most continuous duty applications have been operating at Class B (130degC) temperatures. This paper attempts to evaluate the merits of operation at high temperatures and through aging test assessment, with a polyesterimide mica system for use at Class H temperatures for HV machines, which has been successfully utilized in the field for over four years