This motor driven type series fan is mainly composed of impeller, casing, air inlet, motor and other parts. In addition to the above structure, 6C and 8-20 have a transmission part, which has the highest rate and low noise. Stable performance curve. 1. Impeller-It consists of 10 backward tilting airfoil blades, curved wheel cover and flat back plate. It is made of steel plate (cast aluminum alloy for B4-72). It is highly efficient after dynamic and static balance correction and operation test Stable and reliable operation and good air performance. 2. Chassis-made into two different forms, of which 2.8-12 # chassis is made as a whole and cannot be folded. 16—20 # is made into three-open type. In addition to being divided into two halves according to the horizontal, the upper half is divided vertically into two halves along the center line. They are linked by bolts so that the impeller can be put in or taken out during installation and maintenance. 3, air inlet-the overall structure, installed on the side of the fan, the cross-section parallel to the axis is a curved shape, the role is to make the air flow into the impeller smoothly, and the loss is small. 4. Transmission-It consists of main shaft, bearing box, rolling bearing, pulley or coupling.