The timing should allow the motor to get up to full RPM in the star configuration before switching to delta configuration. Depending on the motor size and inertia loading it will be from 5 to 10 seconds.

The transition from star connection to delta connection requires that the current flow through the motor is interrupted. This is termed "Open Transition Switching" and with an induction motor operating at partial speed (or full load speed), there is a large current and torque transient produced at the point of reconnection. This transient is far worse than any produced by the DOL starter and can cause severe damage to equipment and the supply.

packet switching

circuit switching

message switching

There are three type of switching system such as circuit switching ,packet switching , massage switching.