Abstract: In the indirect -field oriented control （IFOC） system of induction motor with poor PI speed controller set -ting‚oscillation may occur due to the existence of Hopf bifurcation if the motor rotor resistance can not be exactly esti -mated．In this paper‚conditions of Hopf bifurcation happening were analyzed according to the Lyapunov stability theo-ry‚and principles for proper PI speed controller setting were deduced．Influence of d axis stator current reference on Hopf bifurcation was also discussed．The validity of the above analyses was finally proved by simulation results．The conditions of Hopf bifurcation happening can be used as the guidance for PI speed controller design for the purpose of improving the stability and reliability of IFOC system．

Key words: Hopf bifurcation, induction motor, indirect -field oriented control, PI speed controller