This paper proposes a wye-delta soft start method of
the three-phase induction motors and its control device based on
SCR switches. Comparing with traditional wye-delta start, this
method can suppress inrush current effectively both in the initial
stage with wye connection and the transforming stage from wye
to delta. With the sequence trigger control strategy of SCRs, the
smooth transition of the magnetic flux and lower inrush current
can be realized. Furthermore, this paper also discusses the best
transforming point from wye to delta connection on the basis of
comparison of start current wave at various slip of motor. And
the method