Star Delta starter is the most widely used application especially for Air-compressor and HVAC system.This starter used for 6 or 12 wire for motor terminal depend on electric motor that chosen for the application.
Basically this starter used 3 unit contactor,1 unit timer delay,1 unit overload relay and start/stop button to control the star delta motor.Around the world,it have many types of control circuit design for star delta.
It have different design and technique for the control circuit but the main objective is same,to reduce starting inrush current.
For safety condition for the star delta control circuit,it include with interlock for star and delta sequence to avoid serious damage for electric motor.That mean during star sequence,contactor for delta cannot energize or vise versa. read more