What is the FG (Frequency Generator) of cooling fan

Fan speed is defined as the number of rotations made by the fan blades per minute and is measured in revolutions per minute(rpm). It is influenced by various factors including coil turns in the motor, operating voltage, blade count, angle, height, diameter, and bearing system. Importantly, there exists no direct correlation between fan speed and overall quality. Fan speeds can be assessed internally via speed signals or externally through additional instruments that measure rotation rates; however, internal measurements often exhibit a greater margin for error.

Frequency = speed / time

Cooling fan rpm is 3500, F=3500r/60s=58.3r/s=58.3Hz

Why might there be discrepancies between FG feedback signals and manufacturer specifications? The FG (speed feedback) signal generated by a fan typically manifests as a pulse signal reflecting its rotational velocity; this frequency generally correlates with actual performance metrics. During operation, alternating N and S poles within the rotor induce fluctuations in voltage levels—higher speeds result in more rapid changes in these levels. Variations among manufacturers regarding magnetic pole pair counts can lead to differences in reported rotational speeds at identical FG frequencies; for instance, if one manufacturer employs 4 magnetic pole pairs while another utilizes 6 pairs at equivalent frequencies, their respective actual speeds may diverge significantly.