Transmitted Power of Piping and Wiring in Hydraulic, Pneumatic, and Electric Drive Systems

(Considerations for Loss in Pipes and Wires)

Abstract

Loss is an important factor in power transmission lines of fluid power and electric drive systems that determines the efficiency of mechanical and electrical systems. Although the power rates and torque-to-inertia ratios of hydraulic actuators and electric motors have been extensively investigated, power density and loss in power transmission elements in fluid power and electric drive systems have remained unclear. In this work, the transmitted power values of hoses in hydraulic systems, tubes in pneumatic systems, and cables in electric drive systems available in the market were compared by a simplified model. The flow loss in hydraulic and pneumatic circuits and the electrical loss in electric circuits were considered. The outer diameter, mass per unit length, mean flow velocity, and rated voltage were selected as main parameters. The pressure and voltage drops were calculated on the basis of the pipe friction and electrical resistance and the loss and power were estimated. The results showed that the ratios of the resistance losses to the transmission power for a pneumatic circuit and an electric circuit are comparable to the ratio for a hydraulic circuit in some cases. The transmittable power with loss for hydraulic, pneumatic, and electric drive systems can also be approximated by a power function for the mass per unit length and the outer diameter.