Motor failures due to steep fronted switching surges-the need for surge protection-users experience

Steep fronted wave surges cause severe stress on the installation of the stator windings of large AC motors due to the nonuniform distribution of voltage across windings. The absence of acceptable national standards defining the impulse voltage withstand capability of rotating machines, as applied on static equipment, has led to inconsistency, uncertainty, and failures of many such motors. Based on available technical literature, recent national studies, and user experience, the need to specify extra dielectric strength for turn-to-turn insulation to withstand the overvoltages and the need for acceptable national standards and testing requirements are presented