Could some one please explain me the Advantages & Disadvantages of having Soft starters instead of conventional auto transformer & star delta starter's?
You reduce your parts count. One soft-starter replaces three contactors (plus other peripheral devices).
Other advantages of using a soft-starter is the ability to choose the start up mode. Your soft-starter manual can explain those better than I can.
Then there's none of that annoying "THUD" as the contactors engage and disengage. I forget the number of times it made me jump while testing a 440V line.
In relation to that, the vibrations caused by contactors engaging and disengaging can accelerate loose connections in terminals. This is why we have "terminal tightening exercises" every few months or so.
In addition to reduction of components and noise during starting, the starting current will also get reduced when compared to DOL starting or Star/Delta starting.
"Everything you can imagine is real." -- Pablo Picasso