Tähtikolmiokäynnistin

Tähtikolmiokäynnistin, often referred to as a star-delta starter, is a type of motor starter used for starting three-phase induction motors. It is employed to reduce the starting current drawn by the motor. Direct on-line starting can cause a very high inrush current, which can be problematic for the electrical supply system and the motor itself, leading to voltage dips and increased stress on motor windings.

The star-delta starter operates by initially connecting the motor windings in a star (Y) configuration. In this configuration, the voltage across each winding is reduced to 1/√3 (approximately 58%) of the line voltage, and consequently, the starting current is also reduced to about one-third of the current drawn during direct on-line starting. After a predetermined time, or when the motor has reached a sufficient speed, the starter reconfigures the windings into a delta (Δ) configuration. In the delta configuration, the motor then receives the full line voltage and operates at its normal rated power.

The primary benefit of using a star-delta starter is the significant reduction in starting current, which helps to prevent overloading of the power supply and reduces mechanical stress on the motor and driven load. This method is most effective for applications where the motor is lightly loaded during startup or where the load can be applied gradually. It is a cost-effective solution for starting medium-power induction motors in various industrial applications.