Stabilization and speed control of a hypersynchronous doubly-fed motor: tests and experimental results

An experimental research work is carried out in order to overcome the inherently unstable behaviour of doubly-fed hypersynchronous motors. The authors deal with the developed method which uses a frequency converter supply of either the rotor or stator winding of the machine, while the other machine winding is connected to the grid. The authors discuss the required control algorithm, and present the results of experimental tests carried out on a 6 hp machine. These results show that stable motor running conditions can be achieved, and converter operations allow a suitable control of the rotor speed over the synchronous speed set by the grid frequency