Patent ID: 7508150

Claim:
An electric motor controller comprising: detecting means for detecting rotational speed of an electric motor; storage means for storing the rotational speed detected by the detecting means; calculating means for calculating a difference between a present rotational speed output from the detecting means and plural past rotational speeds stored in the storage means; first judging means for judging whether the difference between the present rotational speed and a most past rotational speed that is calculated by the calculating means is larger than a first threshold value; second judging means for judging whether at least one of plural differences calculated by the calculating means is larger than a second threshold value; third judging means for judging based on the judgment results of the first judging means and the second judging means whether rotation abnormality occurs in the electric motor; and control means for controlling the electric motor in accordance with the judgment result of the third judging means, wherein the first threshold value and the second threshold value are values for detecting a deceleration trend of the rotational speed of the electric motor, the first threshold value is set to be smaller than the second threshold value, and when both the first judging means and the second judging means make positive judgments, the third judging means judges that rotation abnormality occurs in the electric motor.