an investigation of dual stator winding induction machines

associated with rotor misalignment, rotor shaft bending, weak bearings and
manufacturing tolerances. The behavior and the performance of induction machines
under rotor eccentricity conditions have been a subject of recent investigations.
Generally speaking, the air gap eccentricity can be classified as: static eccentricity,
dynamic eccentricity and mixed eccentricity [4.4]. The diagram of different eccentricity
conditions are shown in Figure 1.2. In the uniform air gap condition, the center of the
rotor and the center of the stator have the same location as shown in Figure 1.2(a).
However, the location of the centers of the rotor and stator are not the same under all
eccentricity conditions. The differences between the eccentricity conditions are explained
as: under static eccentricity condition, the rotor still rotates around its own center axis and
the air gap is not uniform as shown in Figure 1.2(b). The rotor rotates around the stator’s
center axis under dynamic eccentricity condition. The central axis shown in Figure 1.2(c)
is the one for the stator. For mixed eccentricity condition, the rotor will still rotate around
the rotor’s central axis while the rotor’s central axis rotates around stator central axis.
Both the central axis of the rotor and stator are shown in Figure 1.2(d) and the possible
rotating behaviors are represented by arrows.
Some of the previous works focus on the definitions of the air gap and the
approximation of the inverse of the air gap, the determination of the harmonic
components present in the machine variables (currents, torques etc.) due to rotor
eccentricity, the computer simulation of the machine under eccentricity and the
evaluation of the inductances [3.7-3.9, 4.1-4.6]. Based on the winding function method
and coupled-circuit model simulation, the modeling methodology of the induction
machine under eccentricity conditions has been proposed in [3.7].
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