Analysis of the Concentric Planetary Magnetic Gear

In the field of electric machine design, a trend in many applications has been to design machines with increasing torque density. When machines fail to meet torque density requirements or are simply incapable of matching load torque, gears are commonly used. Magnetic gears have been proposed as a means of increasing torque density within electromechanical systems, while avoiding problems associated with traditional mechanical gears. While the idea behind magnetic gears goes back to early patents, their study and use in industry has been very limited to date. This study looks into variations of the gear which could lead to more industrial use. The effect of pole count upon torque ripple is investigated with finite element analysis (FEA). The analysis is extended to new magnetic layouts which borrow from permanent magnet machine design. One of the most critical components of the gear, the stator pole pieces, are also investigated for variations which aid in construction while maintaining the performance of the gear. As a means of supplementing analysis of the gear, winding function theory (WFT) is used to analyze the gear. Winding function theory has enjoyed success with induction, synchronous, and even switched reluctance machines in the past. This study is the first of its kind to apply winding function theory to a device devoid of windings altogether. It is shown that this method is capable of generating the stall torque and steady-state torque ripple waveforms which have been commonly attempted with FEA. While magnetic gears enjoy distinct advantages over mechanical gears such as inherent overload protection, they are not as torsionally stiff as their mechanical counterparts. As such, the use of damper windings for the purpose of stiffening the gear against transient oscillations is also investigated. Several competing designs are investigated for their performance, and a final design is studied which is capable of arresting transient oscillations in less than a second. In addition, a prototype has been fabricated and will be used to verify the analysis undertaken. The prototype is used to verify variations of the stator pole pieces as well as the inner rotor magnetic layout. A dynamometer has been assembled to test the performance of the prototype. A new design is also proposed for future work.