What reduces the starting current of a motor using star-delta configuration?

In a star-delta starter configuration, the starting current of a motor is reduced primarily through the technique of switching winding configurations. When a motor starts in a star configuration, the windings are connected in such a way that each winding receives only a fraction of the line voltage (specifically, 1/√3 or about 58% of line voltage), which leads to a significant reduction in current draw at startup.

Once the motor reaches a certain speed, usually around 70-80%, the connection is switched to delta configuration, allowing the motor to operate at full line voltage and achieving full torque. This transition effectively minimizes the starting current, which helps reduce stress on both the motor and the connected electrical supply. By limiting the inrush current at startup, the star-delta configuration protects the motor from potential damage and ensures smoother operation during ignition.

The other options do not provide the same effect on reducing starting current as the star-delta configuration. For example, increasing the voltage would actually elevate the starting current, and adding resistors could limit performance rather than reducing starting current effectively. Using capacitor start motors is a different approach altogether, primarily utilized in single-phase motors for improving starting torque, rather than addressing starting current in the context of three