Why delta connections are done when the motor is required to be operated at 220V?
The tip dresser motor phases are wound for 220 V.

To run it on 3 x 220 V, the phases are to be delta-connected.


Since the line voltage is 220 V, each phase of the motor is fed 220 V.

To run it on 3 x 380 V, the phases are to be star-connected.


With a line voltage of 380 V, the phase voltage would be 220 V (380 / √3 = 220).
Thus each phase is still fed 220 V.