Modeling and Analysis of Unbalanced Magnetic Pull in Cage Induction Motors With Curved Dynamic Eccentricity

The unbalanced magnetic pull (UMP) often occurs in different kinds of electrical machines. In induction motors, UMP is usually caused by air-gap eccentricity, which is generally divided into static eccentricity, dynamic eccentricity, mixed eccentricity, and inclined eccentricity, also known as rotor misalignment. However, it has been verified that the curved dynamic eccentricity always occurs to some extent where the shaft in the majority of large electrical machines is bent, such as submersible motors. The curved dynamic eccentricity is defined as a condition in which the degree of dynamic eccentricity varies along the axial direction, and the eccentricity in the middle part of the motor is larger than that of the ends. Therefore, this paper presents a new method to calculate the UMP in cage induction motors, considering the curved dynamic eccentricity. Finite-element method is adopted for verification.