What is the name of the reduced voltage starting technique that employs a resistor in series with each motor supply phase?

The reduced voltage starting technique that employs a resistor in series with each motor supply phase is known as primary resistor starters. This method is specifically designed to limit the initial inrush current that occurs when an electric motor starts, which can be several times higher than the motor's full-load current. By introducing resistors in series with the motor, the voltage across the motor is reduced during startup, effectively controlling the starting torque and current.

As the motor accelerates and approaches its rated speed, the resistors can be bypassed, allowing the motor to operate at full voltage. This technique is beneficial in applications where minimizing mechanical stress on the motor and connected equipment during startup is important. It is a widely used method for starting induction motors, particularly in systems where a more gradual acceleration is advantageous.

Other options do not specifically describe the method of using resistors in series with each supply phase. For instance, autotransformer starters involve varying the voltage supplied to the motor through a transformer setup, while soft starters utilize electronic controls to gradually adjust the voltage and current rather than relying on physical resistors. Closed transition starters typically involve switching between starting configurations with minimal disruption, rather than directly inserting resistors in the motor supply.