Chapter XII electrical machinery and transformers

Most work concerning insulation for rotating electrical machinery during 1957 has been attributed to the various testing methods used for evaluating the quality of the insulation. Several surveys have appeared comparing the different test methods. Wichmann describes a method of separating the insulation current from the superposed polarization current appearing in d-c testing} and Fabre describes the polarization phenomena and presents curves of the variation of polarization current with time} between 10 and 105 sec.