Rotatory Field

A magnetic field whose virtual poles keep rotating around its centre of figure. If two alternating currents differing one quarter period in phase are carried around four magnetizing coils placed and connected in sets of two on the same diameter and at right angles to each other, the polarity of the system will be a resultant of the combination of their polarity, and the resultant poles will travel round and round in a circle. In such a field, owing to eddy currents, masses of metal, journaled like an armature, will rotate, with the speed of rotation of the field.