A starting circuit that reduces the voltage of the synchronous motor resistance and adds excitation according to the change of the stator current.

188. This is a starting circuit with added excitation that uses the stator current value to reflect the motor speed, as shown in Figure 3-188.
    In the figure, tKA is an undervoltage relay. When the grid voltage is low to a certain value, KA is released, causing the contactor KMz to close,
short-circuiting the magnetic field resistance R:, and the DC generator output increases (ie, strong excitation). The excitation current of the synchronous motor increases, thereby ensuring
the normal operation of the synchronous motor.