When the selector switch 1S1 is turned towards hand and the overload relay is not in trip position, the star contactor 1KM3 is turned on instantaneously, The timer IT2 and the main contactor 1KM1 are now turned on through the auxiliary contact of 1KM3.

Indication lamps (1L1, 1L2): For starter status indications.

Star delta timer (1T2): Timer that switches the star and delta contactors.

Coil and auxiliary contacts of Main (1KM1), star (1KM2) and delta (1KM3) contactors.When turned towards hand mode, the starter is triggered immediately and when turned towards auto, the circuit is triggered only when an external command is received from BMS/PLC/DCS.

Operation mode selection switch (1S1).The control circuit of the starter consists of the following components: Contractors : Main (1KM1), star (1KM2) and delta (1KM3).MCCB (Q1) : Protects the circuit from short circuits.The power circuit of the starter consists of the following components: The diagram can be divided into two parts: The power circuit & control circuit. The wiring diagram for a 132kW star-delta starter used for a condenser pump is shown below: Star delta starter wiring diagram Further operation in detail can be found here: Star-delta starter (Wye-Delta Starters) – Circuit, working. You can find the instructions to calculate the ratings of contactors for a star-delta starter circuit here: Star-Delta starter design tool. The power and control circuits of a star-delta starter are discussed in this article with the help of an actual star-delta starter wiring diagram.

Siemens star delta timer wiring diagram