Detection of Broken Damper Bars of a Turbo Generator by the Field Winding.

This paper completes the existing Diagnosis Systems of synchronous machines. In order to avoid break downs caused by broken damper bars, a method to diagnose such failures is presented. The main idea of this method is the separation of pole voltages of the field winding according to its polarity. By it, the difference of the pole voltages can be determined. This difference voltage is caused by the noise field of the missing damper bar because the main field of a symmetrical built machine disappears in the difference voltage. The broken damper bar is fixed on the rotor and the field winding is fixed, too. Moreover, the difference voltage depends as well on the position of the missing damper bar as on the distribution of the field winding. In the case of a distributed field winding, the damper bars under the edges of each pole can be detected exact. In order to check the bars in the middle of each pole additional measuring coils of each bar are needed. These coils work according to the measuring method of the field winding. The theoretical ideas are checked by measurements at a special adapted test machine.