Fig. 9 Influence of CPL on Dominant Pole
The variation of the damping ratio with the drive output
torque and speed is illustrated in Fig. 10 when the drive and
converter current control loop bandwidths are set to 800 Hz
and 1 kHz, respectively, and the speed and voltage control
loop bandwidths are 267 Hz and 83 Hz respectively. The
worst case condition is at the peak torque of 15Nm and full
speed of 1500 rpm. However, the system can be unstable at
the full torque even the speed and hence the power is very
low. This highlights the need that a comprehensive design
assessment is necessary in order to ensure that the system
operates stably in all possible conditions.