The magnitude of the voltage induced in the stator winding is, as shown above, a function of the magnetic field intensity, the rotating speed of the rotor, and the number of turns in the stator winding. An actual description of individual coil design and construction, as well as how the completed winding is distributed around the stator. In this section a very elementary description of the winding arrangement is presented to facilitate the understanding of the basic operation of the machine.
As stated above, coils are distributed in the stator in a number of forms. Each has its own advantages and disadvantages. The basic goal is to obtain three balanced and sinusoidal voltages having very little harmonic content (harmonic voltages and currents are detrimental to the machine and other equipment in a number of ways). To achieve a desired voltage and MVA rating, the designer may vary the number of slots, and the manner in which individual coils are connected, producing different winding patterns. The most common winding arrangement is the lap winding, and it shown in Figure 1.21.
A connection scheme that allows great freedom of choice in designing the windings to accommodate a given terminal voltage is one that allows connecting sections of the winding in parallel, series, and/or a combination of the two. Figure 1.22 shows two typical winding arrangements for a four-pole generator.
