Phase Sequence

Author: E.E. Kimberly

In Fig. 9-1 (a), the emf in conductor 1 is at its maximum value. After 120 degrees more of rotation, the emf in conductor 3 will be maximum in the same sense. After an additional 120 degrees the emf in conductor 2 will be maximum in like sense.

The emf's in these conductors are said to have a phase sequence of 1, 3, 2. If the direction of rotation were reversed, the phase sequence would be 1, 2, 3. The phase sequence of a three-phase power source is important in the application of three-phase induction and synchronous motors described in Chapters 18 and 19 because the direction of rotation of such motors is determined by the phase sequence of the applied voltages.