The formula to calculate the frequency of an alternator is:

f = (P × N) / 120

Where: f = frequency in Hertz (Hz) P = number of poles N = rotational speed in revolutions per minute (RPM)

In this case, we have: P = 6 poles N = 1500 RPM

Therefore, the frequency of the 6 pole alternator running at 1500 RPM is:

f = (6 × 1500) / 120 f = 9000 / 120 f = 75 Hz

So, the frequency of the 6 pole alternator is 75 Hz.