about 1000 to 5500 rpm and accelerations are generally under about 200 rpm ms fig6 a shows the same samples on a more compressed vertical scale and fig6 b shows the distribution of current for the same sample times the distribution of current is complex but it will be noted that the maximum current is between 80a and 90a fig7 a and 7 b show corresponding samples when the motor 110 is experiencing a locked rotor condition as can be seen the estimated acceleration shown on the vertical axis is much greater when the rotor is locked and the sensorless algorithm 112 is not operating correctly the velocity is displayed on the horizontal axis and it can be seen that when the rotor is locked a velocity is still generated because of the false variation in the position estimation however the majority of motor speed values are below 1500 rpm and a large number are below 1000 rpm i e below the normal operating speed range of the motor also a large proportion of the samples have acceleration values of 200 rpm ms or greater also the values for current are much higher than those in fig6 b with a large number of samples having currents above 100a this change in estimated acceleration magnitude can be used as an indication of stalling and a threshold placed on the acceleration signal if the absolute acceleration exceeds this specific threshold then the stall detection algorithm detects a stall condition the estimated acceleration of the motor is defined as the change in motor velocity since the previous calculation divided by the time since the last velocity.