Based on the analysis above, it can be seen that 2-phase
conducted and 3-phase conducted state of stator windings are
frequently alternated both in the process of wye soft switching
and wye-delta soft transform. In order to research deeper, it is
necessary to establish unbalanced mathematic model for 2-
phase conducted and balanced model for 3-phase conducted
respectively.
Mathematic models are established based on following
assumptions:
a). Neglecting saturation effect, hysteresis and eddy
current losses.
b). Neglecting the effect of slots and nonlinear problems
of motor parameters.
c). The rotor speed (nr or ωr) is constant during wye soft
switching and wye-delta soft transforming stage.
The mathematical model describing the