Energy "Axial Fan" is usually provided by the head, said total pressure is called, refers to the value added by the unit volume of gas after the fan energy, represented by the symbol p, the unit is Pa. Power can be divided into effective power and shaft power. Effective power refers to the power per unit time fan of the fluid obtained, that the fan output, with Pe expressed in units of kw. That is the prime mover shaft power transmitted to the fan shaft power, also known as the input power represented by Pa. Determination of the shaft power is usually electric logging method, which uses the power meter measured a prime mover input power P'g.