In a four-pole AC generator, how many cycles per mechanical revolution are produced by a single loop?

In a four-pole AC generator, how many cycles per mechanical revolution are produced by a single loop?

• A. One
• B. Eight
• C. Two
• D. Four

Answer: (C)

Electrical cycles per mechanical revolution come from how many pole pairs the rotor presents as it turns. A four-pole rotor has two pole pairs around the circumference, so as the rotor makes one full turn the coil experiences polarity reversals that complete two full cycles of the induced emf. In other words, cycles per revolution equal half the number of poles, so a four-pole machine yields two cycles per turn. (Frequency relates to rpm by f = P × rpm / 120, which ties speed to the number of cycles produced per second.)

Electrical cycles per mechanical revolution come from how many pole pairs the rotor presents as it turns. A four-pole rotor has two pole pairs around the circumference, so as the rotor makes one full turn the coil experiences polarity reversals that complete two full cycles of the induced emf. In other words, cycles per revolution equal half the number of poles, so a four-pole machine yields two cycles per turn. (Frequency relates to rpm by f = P × rpm / 120, which ties speed to the number of cycles produced per second.)