Some new technology is so out of the ordinary that it seems like a solution looking for a problem. Programming magnets is one such capability.
Correlated Magnetics Research has developed a method of fully magnetizing small areas on magnetic materials and arranging these magnetic elements, or “maxels” as the company calls them, into patterns so that the resulting magnetic device is tailored to a particular task. For instance, magnets can be programmed to attach in a particular orientation, or only to other magnets similarly coded. A designer might use these coded magnets to enable the assembly of structures without mechanical fasteners and only in the way the designer intended. The process essentially delivers custom magnetic fields of almost any shape and intensity. The maxels currently can range from 0.5 to 8-mm diameters. A programmed magnet may have as few as three and up to many thousands of maxels.
The technology, developed by co-founder and CEO Larry Fullerton,
A Polymagnet field scan shows a complex polarity arrangement (red for north and blue for south). Precisely placed maxels produce precision magnetic fields, and therefore, resulting forces. These magnets will seek a particular alignment, deliver a tailored coupling force and allow specific release-force characteristics, all to produce unique magnetic identities to control how magnetic structures interact.
raises the possibility of making complex alternating magnetic fields like those found in wind-turbine generators. The difference would be a high-pole-count rotor could be made from a single magnet, or perhaps fewer chunks of magnetic material. In addition, the fields set up by the magnetic rotor could be tailored to vary smoothly and rapidly as the poles transition from north to south, making wind-turbine generators more efficient. A 30-pole generator prototype provided the proof of concept.
“Turn its crank at two turns per second and you get 60 Hz power, or if you put 60 poles along the circumference, one turn per second generates 60-cycle power,” company Vice-President Ron Jewell said. “We have seen interest for small-scale wind generators as a residential application, and small, portable generators for charging batteries – todays’ soldiers carry a lot of batteries, for example. This printed-magnet approach might serve larger wind-energy generators as well.”
Magnetic coupling sufficient to transfer large amounts of torque between rotating surfaces would accomplish a lot of work, but would experience no wear and would need no lubrication. Such advanced research is ongoing at CMR under contract to the U.S. Navy. Large wind turbines might use this technology to couple the rotor shaft to the gearbox or the gearbox to the generator. A torque-limiting capability in such a coupling would prevent the transmission of shock loads that recent research says is partly responsible for shortening gearbox lives.
Magnetic field viewed from the side of a thirty-pole rotor printed onto a single NdFeB ring by Correlated Magnetics Research. The pole elements are shown as dark regions and the transitions are shown by the light-colored lines between the pole elements This thirty-pole rotor was printed in 11 seconds.
Aside from alternating poles on a generator, magnetic patterns allow for other possibilities. “The technique allows making patterns that attract or repel, or attract and repel simultaneously,” Jewell said. “Magnets can be designed to lock together in space without surface contact, using a code pattern we call Hoverfield.”
“We’re continuously developing new behaviors and discovering new applications,” Jewell said. For instance, one application under study for the Hoverfield code pattern is as a vibration isolator. Another pattern can form a linear detent – like the vent stops in a screened window. The company has also shown how magnets with patterns of maxels can use much less magnetic material to accomplish a particular task when compared to standard magnets. For example, coupling and shear force improvements exceed 600% over conventional single dipole magnets in certain applications.
To investigate the almost unlimited combinations of magnet patterns, the company has created a spot-magnetizer they call a MagPrinter that uses a proprietary magnetization coil, or “print head,” to place magnetic elements into hard materials such as rare-earth magnets. The company has designed software that helps a magnet designer sketch out a code pattern and then vary voltage inputs to precisely control the saturation (amplitude) of the maxels.
The cutaway view is of a prototype hand-crank generator capable of 60-cycle power.
The size and shape of a maxel is the result of the size of the print head, the magnetic material and the voltage used to create it. A softer material produces a larger maxel compared to a harder material using the same print head and voltage setting. The process works with many materials from rare earths to ferrites to flexibles. A 2mm print head can make hundreds of elements on a small magnet, which greatly accelerates exploration of the large number of potential code patterns.
“We are currently printing a wide variety of maxel sizes. It only takes about 15 micro-seconds to induce the field. The pulse is so short that any heat is dissipated rapidly and does not build up on the device. In the lab, we are printing typically at 10 to 15 maxels per second, so combined with the automated design environment, you can completely design a magnet concept in a matter of minutes,” says Jewell. WPE
Filed Under: Generators, News
