Siemens Star Delta Contactor is a device that is mainly used to reduce current demand during motor startup. It is most often used for starting three-phase induction motors that can only be used when starting the motor without load and when the required starting current is relatively low. Siemens Star Delta Contactor is a very common type of starter that is extensively used for starting squirrel cage induction motors. These are used for starting a cage induction motor that is designed to run normally on delta-connected winding.