Achieving High Gear Ratios for Magnetic Gearboxes

A magnetic gearbox (MG) can operate with low noise and vibration, and any kind of non-contact operation eliminates the need for gear lubrication. In addition, MGs have the potential for high efficiency and have a unique ability to pole slip when overloaded rather than catastrophically failing, which in turn, provides built-in overload protection.

Coaxial MGs have experimentally been shown to be capable of achieving active region torque densities above 200 Nm/L. However, most single-stage coaxial MG designs have only been shown to be capable of achieving a high-torque density at a low gear ratio, typically less than 8:1. The disconnect is there are many applications (think robotics and power generation) in which a significantly higher gear ratio is desirable.

In contrast, mechanical cycloidal gearboxes are well known for their ability to have a high gear ratio and a high-torque density, but the trade off is a relatively short operational life. In 2008, a paper was published demonstrating the capability of a contact-free cycloidal MG (CMG), which enabled field harmonic modulation to be created between two magnetic rotors. More recently, other studies demonstrated the performance of a similar type of CMG with even better gear ratio performance. Nevertheless, there’s been very little research published on the capabilities of CMGs so a team at the University of North Carolina at Charlotte set out to do research to demonstrate that a CMG is capable of achieving a volumetric torque density >200 Nm/L while also operating with a high gear ratio.

Kang Li, a member of the team, presents their approach to designing and simulating a cycloidal magnetic gear with a high gear ratio and a high torque density using Infolytical MagNet.

Click on this link to follow the details of their work.