"Axial Fan" Sp is a comprehensive system piping resistance coefficient (kg / m). Sp resistance depends on the characteristics of the pipeline system, according to the setting of the piping system and resistance calculated and determined. Line performance curve equation is represented by a quadratic parabola through the origin of the coordinate system Pc-Q. Total pressure p represents the total energy provided by the fan, but the loss of energy to overcome the resistance of the piping system can only be total pressure in the static pressure energy. Thus, the fan unit operating conditions determined, and sometimes need to use static versus Discharge fan (Pst-Q) curve to determine the appropriate means conditions. In this case, the fan means will appear full voltage operating point N and static operating point M, correlation shown, this is the meaning of two different operating points.