This paper proposed an algorithm for enhancing the performance of the diagnosis of rotor bar fault and stator winding fault in a squirrel-cage induction motor? through motor current signature analysis(MCSA). The performance of this diagnostic algorithm was also verified through experimentation. An online diagnostic system for these two electrical faults was also developed using the proposed diagnostic algorithm.
Information on the rotational speed of a motor is an essential factor for diagnosing induction motor faults. In this paper, the rotor slot harmonics(RSH) method is used to estimate the rotational speed of an induction motor without a speed sensor.
The results of the RSH technique showed that the estimation error rate of the motor speed is 0.05% or less.
Diagnosing the rotor bar fault in an induction motor under
light-load operating conditions is especially a difficult problem.
This paper proposes the rotor bar fault characteristic frequency under light? load condition.
Experimental results show that the characteristic frequency of proposed is more separate from the supply source frequency than that of under light-load condition. Also the proposed method is more detectable than under heavy-load condition.
For detecting the rotor bar fault, the variation threshold value that was varied according to the load change is suggested. This paper proposes a diagnostic method using the distortion ratio in Park''s vector pattern; this enables diagnosis of stator winding short-circuits by applying a constant threshold value irrespective of changes in the load or capacity. The conventional
method is difficult to set a threshold value with a diagnostic
reference value that varies with changes in the load and motor capacity, whereas the proposed method is very easy to set the threshold value. Since the distortion ratio does not vary with load change.
An online diagnostic system for electrical faults of a squirrelcage inductor motor was developed on the basis of above algorithm. The system was configured to allow a user to easily identify and judge the process and results of the diagnosis of the rotor bar and winding faults.