What is the main purpose of a star-delta starting method?

The star-delta starting method is primarily used to reduce the inrush current when starting a three-phase induction motor. When a motor is connected in a star configuration during startup, the voltage across each winding is reduced to about 58% of the line voltage. This results in a significant reduction in the starting current, which minimizes stress on the electrical infrastructure and reduces the likelihood of tripping circuit breakers.

When the motor reaches a certain speed, it is then switched to the delta configuration for normal operation. Delta connection allows the motor to utilize the full line voltage, enabling it to achieve its rated power output and efficiency. This transition is crucial for motors that are specifically designed to operate effectively in a delta configuration once they have built up sufficient speed.

While the other options may seem plausible, they do not accurately capture the main purpose of the star-delta method. The primary aim is to enable a gradual increase in current and torque during motor startup, preventing excessive demand on the power supply system.