Rotating Magnetic Field

To understand the rotations of magnetic field consider a 2-pole 3-phase stator as shown in Figure 5a. The three phase windings a, b and c are represented by three coils aa^', bb^' and cc^'. A current in phase a winding establishes magnetic flux directed along the magnetic axis of coil aa^'. Similarly, the currents in phase b and c windings will create fluxes directed along the magnetic axes of coils bb^' and cc^' respectively. The three phase currents flowing the winding is shown in Figure 5a . At time instant 1 , the currents of each phase are

(2)

Since, i_b and i_c are negative, crosses must be shown in coil-sides b^' and c^' and dots in the coil sides b and c.The right hand thumb rule gives the flux distribution as shown in Figure 5b . In Figure 5b and the following figures, the thicker line indicates higher magnitude to flux. The

At instant 2 , the currents are

(3)