"Two-phase on" drive operation in a permanent magnet synchronous machine electromechanical actuator

Brushless machine technology provides a new and feasible option for high-power actuation applications historically serviced by hydraulic devices. Two types of brushless permanent magnet machines exist: the brushless DC machine and the permanent magnet synchronous machine. While the brushless DC machine is ideally suited for operation with a "two-phase on" drive, the permanent magnet synchronous machine is ideally suited for operation with a "three-phase on" drive. Within this paper, the impact of the torque ripple induced by using a "two-phase on" drive with the permanent magnet synchronous machine is examined for viability, though not compared with the "three-phase on" drive. The focus application is thrust vector control of the Space Shuttle Main Engines, and test results indicate that such operation is acceptable.