Axial recognize "220V AC Cooling Fan" is actually very simple, divided DC cooling fan and AC cooling fan. It is divided into two types of oil-bearing and ball bearings. Then there is the different voltages. Like people, divided into men and women, in which people are divided into two categories of elderly, middle-aged, youth, children. . . The reason is similar. "220V AC Cooling Fan" in the operating point, the slope of the fan characteristic curve for the minimum, change the system characteristic curve was minimum. Note that "220V AC Cooling Fan" static efficiency at this time (the amount of wind power ÷ × pressure) is the best. Of course, to this point, control is very difficult, there is no longer a fundamental experience will not be completed.