Patent ID: 6831477
Filing Date: 2004-12-14
Classification: G01R

Abstract:
An apparatus for detecting an abnormal condition of an electric motor comprising:motor current detecting means for detecting an actual current flowing through a motor; feedback controlling means for feedback-controlling a target voltage that gives the motor a driving command in accordance with deviation of the actual current from a target current; abnormal voltage estimating means for, based on the target voltage and the actual current, estimating an abnormal voltage estimation value corresponding to a voltage exhibiting an abnormal condition in the motor; commutation frequency arithmetically determining means for arithmetically determining a commutation frequency based on rotational speed of the motor, and number of commutators and number of brushes of the motor; a filter device for changing a filter frequency in accordance with the commutation frequency to filter the abnormal voltage estimation value estimated by the abnormal voltage estimating means; and motor abnormality judging means for determining an abnormal condition of the motor based on comparison of the abnormal voltage estimation value filtered by the filter device with an abnormal voltage value previously stored.