Switching surges in rotating machines

The manner in which the turn insulation of high-voltage line-starting a-c motors may be stressed severely by switching surges is described in this paper in such manner as to give both a physical and mathematical interpretation of the phenomena. The importance of the external circuit as well as the machine characteristics is illustrated. Methods are presented for estimating the severity of the stress and the advisable protection. Considerable test data are shown. The test arrangements are described in detail, because new methods had to be devised to obtain the needed data.