Motor drives provide energy savings when used with ___ loads.

• A. Variable-Speed
• B. Both A and B
• C. Variable-Torque
• D. Neither A nor B

Answer: (B)

Motor drives save energy by letting the motor run only as fast as the load requires, and by reducing voltage and frequency to match that speed. For variable-torque loads, such as fans and pumps, the torque the load needs falls off as speed drops, so lowering speed with a drive reduces power dramatically (for fans the power drops roughly with the cube of speed, with pumps it’s a significant reduction as well). For loads that need different speeds to meet process demands (variable-speed loads), the drive eliminates running at full speed when it isn’t needed, further cutting energy use. Because either type of load can benefit from matching speed to demand, motor drives provide energy savings with both.