In this method, a voltage-dropping reactance is placed in series with the motor during starting. The impedance seen by the power system then is that of the reactance plus that of the motor.

START: R OPEN, S CLOSED
RUN: R CLOSED, S OPEN
CLOSED TRANSITION (R CLOSES BEFORE S OPENS)

Series Reactor Reduced Voltage Starting

Starting Characteristics:

1. Motor terminal voltage is reduced from line voltage.
2. Motor current equals line current.
3. Starting torque is reduced by the square of the terminal voltage.

Applications:

1. Usually on high voltage and large low-voltage motors.
2. Where current reduction requirements are low, or where load torque during acceleration is minimal.
3. May be used for full acceleration or for system voltage recovery.