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

Brushless machine technology provides a new and feasible option for high-po wer actuation applications historically serviced by hydraulic devices. Two types of brushless permanent magnet machines exist: the brushless de machin e and the permanent magnet synchronous machine. While the brushless de mach ine is ideally suited for operation with a "two-phase on" drive, the perman ent magnet synchronous machine is ideally suited for operation,vith a "thre e-phase on" drive. Within this paper, the impact of the torque ripple induc ed by using a "two-phase on" drive with the permanent magnet synchronous ma chine is examined for viability, though not compared with the "three-phase on" drive. The focus application is thrust vector control of the Space Shut tle Main Engines, and test results indicate that such operation is acceptab le.