Y-Delta-Switches are standard stuff.
The starting arrangement is fairly simple and designed to reduce the starting rush current.
The very same windings are first connected in Y, only seeing (sqrt(3)) of the nominal voltage, getting the motor to speed. When it's running stable you switch to delta, getting full torque.
I had to run a 3ph blower unit once. It had a Y/D switch and an old ampere meter going up to 6A I think (small 1.5kW 380V 3ph motor). Switching to Y made the ampere meter jump to the end of the scale. Then you waited until the needle went down (or listened to the motor picking up speed) and finally switched to D. The needle would give a short jerk to "full", go back to a few amps and the motor was running.
