How far apart do the stator coils sit on a three-phase alternator?

• A. 90 degrees
• B. 120 degrees
• C. 180 degrees
• D. 150 degrees

Answer: (B)

In a three-phase alternator, the stator coils are spaced 120 degrees apart. This configuration is essential for achieving a balanced three-phase system, which ensures that the output voltages are equal in magnitude and symmetrically displaced in phase.

By positioning the coils 120 degrees apart, each coil produces a voltage that is shifted by one-third of a cycle relative to the others. This design allows for a continuous and steady flow of electrical power, as the three phases provide overlapping power generation, which helps in minimizing power fluctuations and maintaining a consistent output.

In contrast, if the coils were positioned at 90, 180, or 150 degrees, the alternator would not be able to generate a balanced three-phase output, leading to uneven voltage levels and inefficiencies in power distribution. Therefore, the spacing of 120 degrees is critical in the design and operation of three-phase alternators.