Abstract: Blade pitch of variable pitch blades is changed by an actuator having first and second ac machines. The first ac machine is excited with ac power to apply a motoring torque to a control shaft of the actuator, thereby causing blade pitch to change in one direction. The second ac machine is excited with appropriate power to apply a braking torque to the control shaft, thereby causing blade pitch to change in an opposite direction. When the second ac machine is an induction machine, dc excitation will brake the control shaft. When the second ac machine is a synchronous machine, an ac excitation causing a retarding magnetic field will brake the control shaft.

Abstract: Fault-tolerant apparatus for controlling first and second input members of a mechanical actuator includes first and second electrical machines and at least two controllers. The first and second electrical machines, which apply braking forces to the first and second input members, respectively, are provided with stators having pluralities of isolated phase windings. Each controller is coupled to a phase winding of the first electrical machine, and also to a phase winding of the second electrical machine. Any one controller can excite the first electrical machine to apply the braking force to the first input member or the second electrical machine to apply the braking force to the second input member.

Abstract: A two pole permanent magnet rotor which utilizes a single cylindrical two pole permanent magnet mounted between two end pieces and surrounded by a retaining hoop. The cylindrical two pole permanent magnet, which is made of high energy product material, is "straight through" diametrically magnetized to provide a sinusoidal air gap flux distribution which eliminates losses due to harmonics. The cylindrical two pole permanent magnet may be made of a plurality of smaller magnet blocks which are stacked and machined to form cylindrical configuration.

Abstract: A two pole permanent magnet rotor utilizes a single cylindrical two pole permanet magnet mounted between two end pieces and surrounded by a retaining hoop. The cylindrical two pole permanent magnet, which is made of high energy product material, is "straight through" diametrically magnetized to provide a sinusoidal air gap flux distribution which eliminates losses due to harmonics. The cylindrical two pole permanent magnet may be made of a plurality of smaller magnet blocks which are stacked and machined to form a cylindrical configuration.

Abstract: Apermanent magnet coupling including high strength rare earth-cobalt permanent magnets retained under uniform compression during rotation.