4-4
Figure 4-2.—Two-phase motor stator.
If the voltages applied to phases 1-1A and 2-2A are 90º out of phase, the currents that flow in the
phases are displaced from each other by 90º . Since the magnetic fields generated in the coils are in phase
with their respective currents, the magnetic fields are also 90º out of phase with each other. These two
out-of-phase magnetic fields, whose coil axes are at right angles to each other, add together at every
instant during their cycle. They produce a resultant field that rotates one revolution for each cycle of ac.
To analyze the rotating magnetic field in a two-phase stator, refer to figure 4-3. The arrow represents
the rotor. For each point set up on the voltage chart, consider that current flows in a direction that will
cause the magnetic polarity indicated at each pole piece. Note that from one point to the next, the
polarities are rotating from one pole to the next in a clockwise manner. One complete cycle of input
voltage produces a 360-degree rotation of the pole polarities. Let's see how this result is obtained.
