I. Introduction
Clemson University’s Wind Turbine Drivetrain Testing Facility (WTDTF) houses two dynamometer test benches designed to test full-scale wind turbine nacelles [1]. The smaller of the two test benches is rated at 7.5-MW, while the larger one is rated at 15-MW. Each of these test benches includes devices called load application units (LAUs) designed to apply nontorque loads to the main shaft of the device under test (DUT). Studying the effects of nontorque loads is important because of their contribution to drivetrain failures [2], [3].