Motors vary widely in capacity and efficiency and it's difficult to say exactly when downsizing is appropriate. Many motors are at peak efficiency when operating at around 75 percent of their rated load.
Motors that normally run at 50 percent or more of rated load are probably not good candidates for downsizing, while motors that spend a significant amount of time at less than 50 percent of rated load should be considered.
For example, a 25 hp motor that normally operates at 6 horseppower load (25 percent capacity) has dropped in efficiency from 95 percent to less than 90 percent and should be downsized. Motors that have a lot of variation in loading, however, may not benefit from right sizing.
This simple formula can be misleading, however. In making motor sizing decisions, you must consider a number of other factors including the load on the motor and the operating efficiency at that load point, as well as full load speed in revolutions per minute (rpm) on the current and replacement motor. It's important to accurately measure and evaluate these factors together when assessing the energy-saving potential of downsizing.
First-year operating costs for motors can be higher than their initial purchase price. A new, premium-efficiency motor that's sized correctly can pay for itself by returning dollars to your bottom line quickly, and in the years to follow. Each facility is different, however, and the actual savings can vary. If you're considering a motor upgrade, the Motor Cost Savings Calculator can help you determine your potential cost savings.
© Questline, Inc.