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Doubly-Fed Electric Machines (i.e., electric motors or electric generators) incorporate two multiphase winding sets of similar power rating with an electronic controller supplying bi-directional, speed synchronized, and multiphase electrical power to at least one of the winding sets. As a result, Doubly-Fed Electric Machines are synchronous electric machines by nature with both winding sets actively participating in the energy conversion process (i.e., doubly-fed). Uniquely, Doubly-Fed Electric Machines can operate at constant torque to twice synchronous speed (or twice the power output) for a given frequency of excitation with each active winding set rated at half the total power of the machine (i.e., contiguous operation between sub-synchronous through super-synchronous speed range). Theoretically, the electronic controller is comparably less expensive, more efficient, and more compact than electronic controllers of other electric machine types because only the rotating (or moving) active winding set is controlled, which is half the total power output (or less) of the electric machine. However, Doubly-Fed Electric Machines are very sensitive to the synchronous relationship between speed and excitation frequency and as a result, are susceptible to instability without introducing extraordinary means of control. The Wound-Rotor Doubly-Fed Electric Machines and the so-called Brushless Doubly-Fed Electric Machines are the only examples of Doubly-Fed Electric Machines. Like all Synchronous Electric Machines or any state-of-art efficient electric machines, including the brushless DC or Permanent Magnet Electric Machines, Doubly-Fed Electric Machines require electronic control for practical operation and should be considered an electric machine system or more appropriately, an adjustable speed drive. All other electric machines, including the Induction or Asynchronous Electric Machine, have only one active multiphase winding set and are considered Singly-Fed.