TWO-PHASE PERMANENT MAGNET STEP MOTOR FOR MOTION CONTROL

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A two-phase permanent magnet step motor comprises a permanent magnet rotor having an equal number Nr of magnetic north and south poles defining a fundamental step angle θ=90°/Nr, such that a number of steps per revolution of the rotor is 360°/θ, and a toothless hybrid stator with windings defining a number Ns of stator poles, with Ns being divisible by four and a ratio Nr/Ns=n/4, n being an odd integer. The permanent magnet rotor may comprise a set of rare-earth magnets. Preferably, Nr is at most 10 (i.e., not more than 20 rotor poles). A method of driving the step motor continuously applies successive current phases to the windings with the motor speed being controllable simply by the step pulse rate. The motor can be micro-stepped at low speeds for smooth operation.