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.

Abstract: A torque reaction test system for evaluating the performance characteristics of a test motor by detecting its inertial reaction torque to acceleration and deceleration of the rotor. In one embodiment a test motor, typically at a final assembly stage and contained within a housing where it is inaccessible, is mounted in a rotatable fixture and the torque reaction of the test motor when accelerated and decelerated is obtained. The torque reaction is plotted against time or speed. A torque balance loop provides a feedback current which maintains the test motor housing within the fixture at a predetermined point of rotation and which provides an indication of torque reaction. A further embodiment provides a dynamometer in which a test motor is driven by a drive motor for a rapid run-up time and the torque response characteristics are plotted as a function of time or speed to provide nondestructive determination of system parameters.