Investigation of Minimum Speed-capacitance Requirements of Self-excited Induction Generators for Normal and Series-connected Modes

This paper presents a comparison between the minimum capacitance-speed requirements when operating the wound rotor induction generator in two different modes. The first mode is the conventional one when shorting the rotor winding. The second mode is when connecting stator and rotor windings in series. A steady state modeling of the generator self-excited operation is derived to obtain the required capacitance-speed relation for the series-connected mode. The results are validated experimentally. In addition, the effect of machine parameters on the minimum-requirements relationship has been studied utilizing four different machines (including the one used in the experimental setup) of different parameters as case studies. The results show that the rotor-to-stator turns ratio has a considerable effect on the speed range of the possible operation of both modes.