Stability of variable speed series-connected wound rotor induction motor in super-synchronous mode

This paper investigates the stability issues associated with operating series-connected induction motor in super-synchronous mode. In such a mode, the motor runs exactly at double the synchronous speed in stable range irrespective of load conditions. In addition to special arrangements required to attain such a high speed, instability problems have been practically noted. The given analysis in this paper is based on the validity of a previously presented dynamic model of an inverter fed motor drive system. Effects of supply frequency and motor parameters are studied to investigate instability reasons and suggest solutions, either in operation or in the design.