On what type of rotor does a DC excitation winding typically reside?

A DC excitation winding is primarily found on a salient pole rotor. This design features poles that extend outwards from the rotor shaft, with windings attached. The salient pole design allows for effective mounting of the field windings, enabling the generation of a strong magnetic field necessary for the operation of the machine. This configuration provides significant torque and is crucial in synchronous machines, where control over the magnetic field is essential for maintaining synchronization with the power supply frequency.

In contrast, induction rotors do not have wound field coils; instead, they operate on the principle of electromagnetic induction, where rotor currents are induced by the stator's rotating magnetic field. Permanent magnet rotors rely on the intrinsic magnetic properties of permanent magnets, eliminating the need for additional winding. Slip ring rotors, typically associated with wound rotors, are used in applications where variable speed and torque are required, such as in some first-class and second-class machines but lack the DC excitation winding characteristic. The salient pole design is uniquely suited for the DC excitation setup, making it the correct choice in this context.