Dynamic Eccentricity and Demagnetized Rotor Magnet Detection in Trapezoidal Flux (Brushless DC) Motors Operating Under Different Load Conditions

Brushless dc (BLDC) machines are finding increasing use in applications that demand high and rugged performance. Automotive and aerospace are some such areas where these machines may be used. In this context, condition monitoring of these machines would provide added value. This paper investigates the effect of several potential rotor faults on the current spectrum of BLDC motors with a view to develop an effective condition-monitoring scheme. The effect of load unbalances, misalignments, and varying load torques on the diagnosis of such machines is investigated. A method to estimate the strength of the rotor magnets is also provided. Simulation and experimental results are presented to substantiate that current signature analysis could be a viable tool for diagnosing the condition of BLDC machines.

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