Power reduction and resonance avoidance of Maglev vertical axis wind turbines using attractive type passive magnetic bearings

Abstract

In this paper, a new model of magnetically levitated (Maglev) vertical axis wind turbines (VAWTs) is presented for power generation purposes. The rotor is suspended by two permanent magnet attractive type passive magnetic bearings and one control coil; it is possible to rotate the rotor without any mechanical contact. The proposed model solves the most common problems which are found on the other Maglev VAWTs such as reducing the power consumption during the levitation to zero amperes by the zero-power control method and reducing rotation loss during rotation. In addition, the model has some main advantages consisting in the ability to avoid the resonance at the critical speed and increase the maximum rotation speed by changing the air gap between the rotor and passive magnetic bearings to adjust the radial stiffness of the rotor. The design of the passive magnetic bearings is investigated by the finite element analysis, and the optimum shape is discussed. The results of levitation tests are presented for the model to show the effectiveness of levitation current reduction and the adjustment of radial stiffness. The results of rotation tests show that the resonance can be avoided by changing the radial stiffness which also makes it possible to rotate the rotor over the critical speed. Moreover, the results of free-run tests show that the rotation loss of the proposed Maglev system is quite low.

Keywords

• magnetic levitation
• vertical axis wind turbines
• permanent magnet attractive type passive magnetic bearings
• zero-power axial position control
• resonance avoidance