How does a star-delta starter reduce the starting current of an induction motor? answer: A star-delta starter reduces the starting current of an induction motor by initially connecting the motor windings in a star (Y) configuration during startup. In this configuration, the voltage applied to each winding is reduced to 1/√3 (approximately 58%) of the line voltage, which lowers the starting current to about 1/3 of the current that would flow if the motor were started directly on the line (DOL).
After the motor reaches a certain speed (usually 70–80% of full speed), the starter switches the windings to a delta (Δ) configuration for normal operation at full voltage. This transition ensures the motor runs at its rated power while protecting the electrical network from a high inrush current at startup.
Also read:
Key points:
- Star connection → reduces voltage per winding → reduces starting current (~1/3).
- Delta connection → motor runs at full voltage → full speed and torque.
- Protects motor and reduces stress on electrical supply.
Summary: A star-delta starter temporarily reduces the voltage applied to motor windings during startup, which in turn reduces the high inrush current, and then switches to full voltage for normal operation.