Abstract: A back EMF controlled, synchronous, permanent magnet motor capable of extremely high rotation speeds at high efficiency. The motor includes a permanent magnet flux source and excitation coils for producing a rotating magnetic field mounted on an iron free form to substantially eliminate core loss and resulting rotor drag. Back EMF is determined directly from the excitation and controls the excitation to produce a torque angle of substantially 90.degree. between the magnet and coil fluxes. Coil excitation is used at maximum efficiency and hunting is avoided. The permanent magnet provides a high flux density that also allows a low current in the motor coils and thus reduces coil copper losses to further improve efficiency.