Conventional Radial Flux Coaxial Magnetic Gear (CRCMG)
Inner Rotor
Flux Angle Mapping (FAM) Magnetic Gear
Outer Stator
Cross section of mechanical design of FAM MG prototype
3D printed parts for holding the FPs
Flux Angle Mapping (FAM) Magnetic Gear
One issue with conventional radial flux coaxial magnetic gears is that at high gear ratios (>10:1) the difference in size between the magnets on the inner and outer rotor becomes very large (see the image on left). This makes it hard to optimize the geometry of the PMs since the number of magnets is fundamentally related. If we can break this relationship and make the pole pairs on the inner and outer rotor only differ by 1 then it might provide some advantage. That is exactly what this project was about.
Ferromagnetic Pieces Rotor
Flux plot showing how the flux is “mapped” from the inner magnets to the outer magnets for a sample FAM design
Currently I am still working on assembling the prototype.I have completed the mechanical design in CAD and have 3D printed some of the parts. Since each ferromagnetic piece is a different shape, when the lamination stacks were made, they had to be connected with a outer bridge. The plan is to use the 3D printed parts to hold the FPs in place and then machine the bridge off using a lathe. Hence the 3D printed parts should be as stiff as possible, so I again used carbon fiber reinforced poly carbonate. I will update this page when results are available.
FAM MGs operate using a completely different operating principle as compared to CRCMGs. Essentially, the ferromagnetic pieces are shaped in a way that maps the flux from a inner magnet to the corresponding outer magnet (“red to red” and “blue to blue”). This means each FP is a different size and shape which does complicate manufacturing.
A much more detailed explanation and analysis can be found in my research paper on this topology. The paper can be accessed via IEEE Xplore or directly.