Mitigation of Unbalanced Magnetic Pull in Synchronous Machines With Rotating Exciters

• Published in: IEEE transactions on energy conversion Vol. 36; no. 2; pp. 812 - 819
• Main Authors: Evestedt, Fredrik, Perez-Loya, J. Jose, Abrahamsson, C. Johan D., Lundin, Urban
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.06.2021; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Control systems; eccentricity; Flux density; Magnetic flux; Magnetic pull; Magnetism; magnetization systems; Magnetomechanical effects; Permanent magnets; Reduction; rotating electronics; Rotating machinery; Rotation; Rotors; Stator windings; Stators; Synchronous machines; Unbalance; Unbalanced magnetic pull; Winding; Windings
• ISSN: 0885-8969; 1558-0059; 1558-0059
• DOI: 10.1109/TEC.2020.3015314

A magnetization system with active compensation of unbalanced magnetic pull for synchronous machines with rotating exciters is demonstrated. The system used switched power electronics and a digital control system to control the currents in four rotor pole groups, each consisting of 3 poles. It was mounted on the shaft of a synchronous machine, providing an interface between a permanent magnet outer-pole brushless exciter and the segmented field winding. Measurements of magnetic flux density on each pole face and current control made it possible to control the airgap magnetic flux density to balance the machine magnetically, thus removing flux density space harmonics in the airgap and also the unbalanced magnetic pull. The construction of the system is presented along with results from experiments and simulations. Tests were performed with the stator winding both in series and with two parallel circuits. Approximately <inline-formula><tex-math notation="LaTeX">\mathbf {80\%}</tex-math></inline-formula> reduction of static forces and <inline-formula><tex-math notation="LaTeX">\mathbf {60\%}</tex-math></inline-formula> reduction of dynamic forces between the stator and rotor were observed when the system was running.