Once you need so much power that you are looking at 3kV or more rather than 400v or 690v phase to phase (that transition is soft, but think sort of round the thousand horsepower mark) then you start to see more complex arrangements, such as rotors with switched resistors embedded, stepped series reactors (current limiting chokes that get switched out once up to speed) and so forth. Generally bigger machines have more poles but turn more slowly, and there is more space for clever tricks (and the 'just oversize it' solution becomes less sensible once the heavy cable is a dominant cost compared to a more complex starter). ~That said, note that if the supply can stand the surges, and the mechanics are rigid enough, you can still DOL start a large motor.
However, note that star-delta is falling from favour at the low power end and being replaced by electronics offering variable speed control and smooth slow start. As the electronics gets refined, costs of the method fall, and also the upper limit power level at which that becomes practical is steadily rising.
It may be that there is not a lot of simple star delta gear being installed on new kit at all in a few years time.
Once you need so much power that you are looking at 3kV or more rather than 400v or 690v phase to phase (that transition is soft, but think sort of round the thousand horsepower mark) then you start to see more complex arrangements, such as rotors with switched resistors embedded, stepped series reactors (current limiting chokes that get switched out once up to speed) and so forth. Generally bigger machines have more poles but turn more slowly, and there is more space for clever tricks (and the 'just oversize it' solution becomes less sensible once the heavy cable is a dominant cost compared to a more complex starter). ~That said, note that if the supply can stand the surges, and the mechanics are rigid enough, you can still DOL start a large motor.
However, note that star-delta is falling from favour at the low power end and being replaced by electronics offering variable speed control and smooth slow start. As the electronics gets refined, costs of the method fall, and also the upper limit power level at which that becomes practical is steadily rising.
It may be that there is not a lot of simple star delta gear being installed on new kit at all in a few years time.
