Turbogenerator field winding shorted turn detection by AC flux measurement

A new testing technique for detecting shorted turns in turbogenerator rotors is presented, where the field winding is supplied with power frequency voltage as for a normal impedance measurement. The circumferential flux is measured in the centerline of all slot wedges and compared between individual poles by amplitude and/or phase. When the rotor is removed, the turn short can be localized by evaluating the AC flux distribution over turns. The coils may be accessed through ventilation holes or after disassembly of retaining rings