Three Phase Synchronous Generator:

Practical synchronous generators are always of the 3-phase kind because of the well-known advantages of a 3-phase system. If two coils were located at two different space locations in the stator of Fig. 5.2, their emfs will have a time phase difference corresponding to their electrical space displacement. In Three Phase Synchronous Generator, if three coils are located in the stator of the 2-pole machine of Fig. 5.2 at relative electrical spacing of 120° (or 2π/3 rad), an elementary 3-phase machine results as is shown in Fig. 5.11(a).

The corresponding 4-pole arrangement is depicted in Fig. 5.11(b) where each phase has two symmetrically placed coils corresponding to each pair of poles.

The coils of each phase are series/parallel connected and the Three Phase Synchronous Generator are generally connected in star as shown in Figs 5.12(a) and (b).

Three Phase Synchronous Generator

Three Phase Synchronous Generator

The process of torque production in a machine will be explained already after gaining some familiarity with the rotating magnetic field produced by a current-carrying 3-phase winding.