The difference between AC and DC fan fan

　　The difference between AC and DC fan fan, the former AC power supply voltage becomes alternating positive and negative, unlike the DC fan power supply voltage is fixed, we must rely on the circuit control, so that two sets of coils in turn work to produce different magnetic fields. AC fan supply frequency is fixed, so the rate of change in magnetic silicon produced is determined by the power frequency, the higher the frequency, the faster switching magnetic field, in theory, the speed will be faster the more the number of poles as DC fan speed sooner principle the same. However, the frequency can not be too fast, too fast will cause difficulty in starting. Cooling fan