Experimental results and their simplified analysis on instability problems in PWM inverter induction motor drives

The instability problems often experienced in PWM (pulsewidth modulation) inverter induction motor drive systems are discussed. Experimental results are presented on how the unstable regions and oscillating frequencies are dependent on dead time. It is noted that the experimental results can clarify the physical description of sources of the instability phenomena. It is shown that a switching-type inverter necessarily includes regenerative intervals. Its existence is the main source of unstable phenomena. It is also shown that a stable region can be determined by applying analytical results to a self-excited induction generator.<>