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.

No difference.

Y is used as a symbol to indicate the star connection.

In manual star delta starter, the change over from star to delta does not happen automatically. The operator or user puts on the starter, and after few seconds he pushes a lever or handle to change over to Delta.

In automatic method, change over happens from star to delta using an automatic preset timer.

In manual star delta starter, the change over from star to delta does not happen automatically. The operator or user puts on the starter, and after few seconds he pushes a lever or handle to change over to Delta.

In automatic method, change over happens from star to delta using an automatic preset timer.

DOL, Star Delta, Soft starter, VFD