Wt. Thomson et A. Barbour, ONLINE CURRENT MONITORING AND APPLICATION OF A FINITE-ELEMENT METHOD TO PREDICT THE LEVEL OF STATIC AIRGAP ECCENTRICITY IN 3-PHASE INDUCTION-MOTORS, IEEE transactions on energy conversion, 13(4), 1998, pp. 347-354
The introduction reviews the real practical problems of airgap eccentr
icity in large 3-phase induction motors. On-line monitoring methods fo
r diagnosing airgap eccentricity are also discussed and a state of the
art reveiw on the application of current monitoring to detect airgap
eccentricity is presented. The limitations of the classical MMF and pe
rmeance wave approach for predicting the severity of airgap eccentrici
ty are discussed. The time stepping finite element (FE) method and FFT
analysis technique are used as 'analyses tools' to predict the freque
ncy components in the current (Hz and dB) as a function of static airg
ap eccentricity Excellent agreement is obtained between the measured a
nd predicted frequency components (Hz) in the current spectra which ar
e a function of static eccentricity. The FE method is also used to pre
dict the magnitude (dB) of these frequency components in the current s
pectrum with different levels of static airgap eccentricity. These pre
dictions are much closer to the measured values in comparison to previ
ous attempts using the classical MMF and permeance wave approach. The
contents of this paper will be of particular interest to the manufactu
rers and industrial users of three-phase induction motors.