I found this video useful that explains star delta starters easily and in a creative way.
Here is what you will learn from the video: A problem in 3 phase induction motor in conveyor belt system&will learn how star delta motor starters work , why do we use star delta starters with three phase induction motor ,star delta connection with contactors to make the system automated , how we test the system using Clamp meter (Testo 770-3) to measure the inrush current that cause voltage drop throughout the system and timers used with the circuit.
Hope it helps 