Why are multiple windings (pole pairs) used for each phase of a motor or generator?

• A. To increase torque while keeping speed the same
• B. To reduce power losses
• C. To reduce heat generation
• D. To allow it to spin more slowly but produce the same frequency

Answer: (D)

The key idea is how electrical frequency relates to rotor speed and the number of magnetic poles. The frequency you get at the output depends on how fast the magnetic field cycles as the rotor spins and on how many poles the machine has. If you spin the rotor more slowly but want the same electrical frequency, you can add more pole pairs. More poles mean more magnetic cycles per revolution, so you can achieve the same frequency even with a slower mechanical speed. In short, increasing pole pairs lets the machine run at lower speeds while delivering the same electrical frequency. The other options aren’t the primary reason for using multiple windings; they’re secondary effects that depend on many design factors, not the fundamental relationship between speed and frequency.