The simulations are carried out for wye-delta soft start
with various transform point. And the standard variable for
expressing transforming point is the slip s0 which is the value
just before opening stator winding from wye-connection. For
highlight the effect of soft transform from wye to delta, figure
8 (a)-(e) show only a part of three-phase current waveform in
stator during the wye-delta start corresponding to various slip
s0. In these pictures, region A represents stator current
waveform during wye-delta soft transforming process, and
region B stator current of motor operating in delta form.