The star-delta operates by:

• A. Switching the motor windings from one arrangement to another
• B. Autotransformer action
• C. Energizing the motor winding increments
• D. Adding resistance to the motor secondary

Answer: (A)

Star-delta starting reconfigures the motor windings from one arrangement during starting to another for normal running. When the windings are connected in star, each winding sees only a portion of the line voltage (about one-third of the full line voltage), which greatly reduces the starting current and the starting torque. Once the motor reaches a sufficient speed, the connection is switched to delta so each winding receives the full line voltage, delivering the motor’s full running torque. This method relies on switching the winding configuration, not on adding resistance or using an autotransformer, and it doesn’t involve energizing windings in increments.