Technical data characterize relationship between Ia/In, Ma/Mn i Mmax/Mn for direct start-up at nominal voltage.
For the star-delta start-up this relationships come down about 30%.

Direct start-up:
It is used if there’s no limits for power supply and the machine tolerates without damages big amount of steam during start-up. His kind of start-up is often used with machines which are started-up with full duty (load) and for which moment of force is stable but the speed varies (conveyor belts, lifts)

Star-delta start-up:
This kind of start-up can be used when moment of force is 50% smaller than nominal motor’s power. It is used usually with centrifugal machines (fans, pumps)

Warmth produced at start-up is independent on used system only in case of a little moment of force, otherwise during star-delta start-up bigger amount of warmth is produced and it results in bigger overheating than at direct start-up.