Eddy Current drives from DSI Dynamatic can be used as a reliable means of controlling pump speed by regulating a DC excitation coil on a magnetic rotor, rotating concentrically within a steel drum, driven by the motor at full speed. The slip between the input drum and the output rotor produces a slip loss, proportional to speed. By applying the eddy current efficiency to a centrifugal pump, the resulting loss is less than 10 percent of rated power. There are no input harmonics to induce losses in feeders, transformers and harmonic mitigation equipment or harmonic losses in the motor. Air conditioning is also not required. 800/548-2169; www.dynamatic.com.