A wound-rotor motor is typically started with what condition?

A wound-rotor motor is designed to allow for external resistance to be added to the rotor circuit, which provides control over the motor's starting current and torque characteristics. When starting with all the external resistance in the rotor circuit, this configuration limits the initial current drawn by the motor, reducing stress on the power supply and the motor itself.

At startup, the motor requires a high starting torque to overcome inertia. Adding resistance in the rotor circuit achieves this by lowering the rotor speed, which in turn increases the slip and the induced torque. As the motor accelerates and approaches its rated speed, the external resistance can be progressively reduced to allow for more efficient operation and increased speed. This method not only aids in a smooth start but also enhances the motor's overall performance during its initial operation.

In contrast, starting with no external resistance or with resistances open-circuited can lead to excessive starting currents, potential motor damage, and insufficient torque to initiate movement.