In an alternator, the frequency of the generated output voltage is directly proportional to the speed of rotation of the rotor.

This is because the frequency of the output voltage is determined by the number of magnetic cycles produced per second, which is equal to the number of poles multiplied by the rotational speed.

The relationship between frequency and speed can be expressed as:

Speed = 120f/p

Therefore, if the frequency of the output voltage increases, it means that the speed of the alternator has also increased.

Conversely, if the frequency decreases, the speed of the alternator has decreased. The speed of the alternator and the frequency of the output voltage are directly proportional to each other, not inversely proportional.