Star-Delta Control Box
Star-Delta Control Box
Star-Delta Starter
A Star-Delta Starter is an electromechanical device used to start and control the speed of three-phase induction motors. It initially connects the motor in a Star (Y) configuration to reduce the high starting current, which can be up to six times the motor’s full-load current. Once the motor reaches the desired speed, a timer switches the winding to a Delta (Δ) configuration, allowing the motor to operate efficiently.
The starter includes a control circuit with a timer, contactors, and overload relays to ensure safe and reliable operation.
Operation & Working of Automatic Star-Delta Starter
The Automatic Star-Delta Starter controls the safe starting and operation of three-phase induction motors. When the motor is started, the phase current flows through the MCB/MCCB or fuse, the OFF/ON push buttons, and the interlocking contacts to energize the K3 contactor and timer coil simultaneously. This connects the motor winding in Star (Y) configuration, reducing the voltage on each phase to √3 times less than line voltage, ensuring a safe motor start.
During this initial Star connection, auxiliary contacts prevent the activation of the Delta contactor (K2). After the motor reaches a certain speed (typically 5–10 seconds), the timer contact opens, de-energizing K3 and closing K2, switching the motor winding to Delta (Δ) configuration. This allows the motor to receive full line voltage (400V) and run at full speed.
The starter’s control circuit, including contactors, timers, and auxiliary contacts, ensures smooth, reliable, and safe switching from Star to Delta, protecting both the motor and the electrical system from high starting currents.
