Abstract: In indirect field oriented control (IFOC) of induction motor, with poor PI speed controller setting, oscillations may occur due to the existence of Hopf bifurcation provided the motor rotor resistance can not be exactly estimated. Conditions for the happening of Hopf bifurcation are deduced from the relationships among rotor time constant estimating error, natural undamped frequency and damping ratio of the system. The characteristic of oscillations is described by power spectra of time series. Research results show that there are abundant dynamics in IFOC drive. In different parameter cases the system exhibit stability, periodic or even chaos. The study lays the foundation for either avoiding oscillations to design a stable conventional induction motor drive, or using oscillations to improve dynamic performance and efficiency of drive.

Key words: Hopf bifurcation, Indirect field oriented control, Induction motor, Oscillation, Power spectra