I am using a Eurotherm 690 + drive in sensorless vector control mode to control a small motor. The motor controls extremely well across its entire range. However there is one small problem when I increase the speed from standstill the motor "jumps/judders" as it passes through the 5 Hz. point after & before that point it is perfect. If I reduce the speed below 5 Hz then back up again the "jump / judder" is not there. It only happens when starting from Zero speed. I am quite sure that it is a drive setting that is the cause. If you have any suggestions please let me know.