How to judge by the quality of dc cooling fan

A lot of people when choosing dc cooling fans, don't know how to choose, and the average is optional to find several factories, tests can normal operation can, and then choose the lower price compare. Then how can we discern the stand or fall of quality of dc cooling fan? See current: the same speed, the same voltage, the same air. Current small dc cooling fan is good match. Due to the smaller current, means that the smaller the loss of fan, which is low consumption, low consumption is the main reason due to product permeability ability is strong, good motor enameled wire loss, high copper content D smooth oil high activity. Listen to noise: same speed, voltage, the smaller noise dc cooling fans compare with good, because of the low noise mainly with blades, bearing, oil products, assembly structure and so on. Blade shape design, the better, the air volume will be larger, and the lower the noise; Bearing accuracy is higher, so it is with axial friction is smaller, the more accurate size collocation, lower noise, of course, also can; Low noise, friction small, bearings, shaft core of life will be longer, the life of the dc fan also will be longer. Vibration measurement: the same specification and the rotational speed of the fan, small vibration of dc cooling fans compare with good, dc cooling fan is a high-speed machine, it must have some vibration, no one can guarantee no vibration, the smaller the vibration was made, the better, the smaller the vibration, the fan operation is more stable, the bearing and the smaller the wastage of the shaft core, also can reduce the volatilization of oil or ball bearing wear, life will be longer, of course.