| 摘要 |
An electric motor controller is provided to surely and rapidly detect abnormal rotation of an electric motor. The rotational speed of a motor is detected by a rotational speed detector, and stored in a rotational speed memory. The difference between the present rotational speed output from the rotational speed detector and each of plural past rotational speeds stored in the rotational speed memory is calculated in a plural difference calculator. It is determined by a first threshold value/difference comparing determiner whether the difference between the present rotational speed and the most past rotational speed out of the plural differences is larger than a first threshold value, and also it is determined by a second threshold value/difference comparing determiner whether at least one of the differences is larger than a second threshold value. The first and second threshold values are set to values for detecting that the rotational speed of the motor has a decelerating trend through the comparison with the differences concerned, and the first threshold value is set to be smaller than the second threshold value. When both the first and second threshold value/difference comparing determiners make positive judgment results, it is determined by an abnormal rotation determiner that abnormal rotation of the motor occurs.
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