Think of it as a rotating transformer, with the primary windings residing in a stationary casing (stator) and the secondary conductors attached to an inner shaft (rotor).
Tesla's invention is, in essence, a rotating transformer. Its primary windings reside in a stationary steel casing (the stator) and and secondary conductors are attached to an inner shaft (the rotor).
It is suggested that the excitation transformer power be introduced as the operational power supply for the regulator, and the rotor overvoltage protection of the unit be modified.