What voltage must the motor operate at once it is up to speed with a part-winding starter?

In a part-winding starter system, the motor initially operates at a reduced voltage to limit the inrush current during startup. This method helps in gradually bringing the motor up to speed without causing excessive mechanical stress or electrical issues.

Once the motor has reached its operational speed, it needs to transition to its normal operating conditions. At this stage, the voltage must be adjusted to the normal voltage level so that the motor can perform efficiently and deliver the required torque without straining its components.

Thus, the correct option is associated with the idea of maintaining an appropriate voltage throughout the motor's operation, ensuring it operates under normal conditions after the initial reduced-voltage startup phase.