"wo Phase Alternating Currents

— Two alternating currents of the same frequency, but having a difference in phase of a quarter of a period; a diphase or quarter phase alternating current. If two identical simple alternators have their armature shafts coupled in such a manner, that when a given armature coil on one is directly under a field pole, the corresponding coil on the other is midway between two poles of its field, the two currents generated will differ in phase by a half alternation, and will be two-phased currents; similarly, three-phased currents could be generated by coupling the armatures of three simple alternators so that the corresponding coils on each are equally ‘‘staggered’’ with respect to each other. ‘Two-phase and three-phase currents differ in this respect; the two-phase system requires four wires to connect the generators with the motors, and their action is that of two distinct and separate circuits through which are pa ing simple alternating currents of electricity which act upon the revolving part of the motor like the two cranks on a cro connected engine at right angles to eaoh other, or one 90 degrees in advance of the other.