Engineering research centre
Control of asymmetries in permanent magnet electrical machines
PhD project, 2006-10. Supervisor – Professor T X Mei
It is usually assumed that manufactured 3-phase rotary machines have symmetrical windings. However, because of tolerances in the manufacturing process, the asymmetries between phases may occur. The causes of phase asymmetries can be of mechanical or electromagnetic nature. Furthermore, linear machines with more than 2 phases have inherent asymmetries of phases, which are associated with increased reluctances of the flux paths at the ends of magnetic core.
The dynamic analysis of 3-phase machines is usually carried out using the d-q model which assumes that the machine parameters (inductances) of different phases are symmetrical and almost all latest control systems are developed based on the assumption which can lead to significant torque ripples in the machines with substantial asymmetry properties.
The main objectives of the project include: to develop appropriate modelling methods that take into account of the asymmetries in the electrical machines; to emulate the asymmetrical conditions with a standard permanent magnet motor to ‘re-create’ the torque ripples with the conventional control method; and to develop practical solutions for improved control performance.