Terra Magnetica

Last month I attended the Magnetics 2010 Conference in Florida, where a variety of speakers gave updates on the business and technical side of the magnetics industry. One of these days I’ll actually write up my thoughts on the conference itself, probably in conjunction with my RareMetalBlog parter in crime, Ian London.

In the meantime, however, I wanted to mention that I have now uploaded a PDF file that contains the slides from my talk, titled “Recent Developments in Permanent Magnet Gear Systems & Machines” – click the aforementioned link to download it.

The primary purpose of any gearing system is to convert between speed and torque. Typically using a rotating input power source, we want to either increase or decrease the speed in the output shaft, via a converse decrease or increase in torque – and vice versa. Typical examples of such systems are automobiles [where we want to convert the high speed of the rotary crank shaft in the internal combustion engine to a relatively high torque at the wheels] and wind turbines [where we want to convert the high torque but relatively slow movement of the turbine blades, into the high speed required by typical generators]. This conversion between speed and torque is actually a form of power conversion from one part of the system to another.

A key drawback of using mechanical systems for such conversion is that there is friction, wear and tear. Only a few gear teeth mesh at any one time, the rated torque values are by necessity lower than peak torque because of fatigure issues, and there is a lot of lubrication and maintenance required. In addition, failures of such devices tend to be catastrophic – when a mechanical gearbox fails – it fails!

Enter the magnetic gearing system. With no contact between elements, there is no friction to cause wear and tear. Multiple magnetic poles are engaged and thus the systems are highly efficient at converting power. Input and output shafts can be isolated too, which presents additional options for the mechanical designer.

Going a step further – fully integrating magnetic gears with electrical machines such as motors and generators, results in superior, best-in-class torque densities for any electromechanical / electromagnetic power conversion system. This result makes magnetic gearing a very promising technology for a variety of devices, including the possibility of highly compact, high powered traction motors for in-wheel drives for vehicles. Torque densities of up to 140 kNm / m^3 have been achieved, with the ability to produce up to 35 kW of power in a single in-wheel traction motor.

My presentation in Florida covered the recent developments in this area, including low gear ration and high gear ration systems, the history of research into magnetic gears, as well as some potential applications. These are early days for such systems, but I think it’s only a matter of time before they are widely deployed.

You can download a copy of the paper from here.