Quantifying the Energy Savings Potential of Power Drive Systems (PDS)

The use of adjustable speed drives on motor-driven systems—power drive systems (PDS)—offers possibility for dramatic energy savings in commercial and industrial applications beyond what can be achieved by increasing the efficiency of individual components. However, the adoption of PDS remains limited because of the perception that only variable load (VL) applications can benefit from the energy savings potential. This viewpoint, however, fails to consider other energy savings mechanisms and non-energy benefits that come from the installation of a PDS. This paper leverages recent collaborative work by the Northwest Energy Efficiency Alliance and the National Electric Manufacturers Association (NEMA) to examine how and where PDS are currently being installed, as well as quantify and characterize the potential energy savings associated with PDS in a range of applications—including both inherently variable and inherently constant load cases. The work also characterizes other benefits associated with PDS that, though not directly related to the efficiency of the motor system’s operation, can often have a larger monetary impact than the energy savings. This work suggests significant potential benefit from PDS that are not currently being fully realized in the market and outlines steps that the market can take to help breakdown myths around where PDS “make sense,” including the introduction of a new metric for PDS–Power Index in NEMA MG 10011: Power Index Calculation Procedure—Standard Rating Methodology for Power Drive Systems and Complete Drive Modules that describes the potential energy savings possible from both constant and VL systems.