February 4, 2011
Rochester, NY – The collaboration between Lawrence Livermore National Laboratory (“LLNL”) and Arnold Magnetic Technologies (“Arnold”) began with a theoretical design developed by Dr. Dick Post of LLNL, and became a reality through the manufacturing expertise of Arnold. For the past several months, Arnold and LLNL collaborated on designing, building, and testing a prototype passive magnetic bearing system. The objective of the Arnold / LLNL relationship was to prove Dr. Post’s analytical code work by making and testing a working prototype of one embodiment of the magnetic bearing. Once validated, these codes can be used in the design of passive magnetic bearing for multiple applications on a variety of scales. (Arnold Magnetic Technologies Corporation and Lawrence Livermore National Laboratory Collaborate on Passive Magnetic Bearing System, May 26, 2010).
The prototype design involves two precision-machined plates, each nineteen inches in diameter, which encase magnetic Halbach arrays. In the final assembly, the plates face each other and are aligned such that opposing magnetic fields create a central equilibrium plane between them. A stabilization force is created in this region and a passive magnetic bearing is created. The permanent magnets in these arrays are made of high magnetic field strength material and are precision ground to tight tolerances in order to fit into the machined slots in the plates.
Due to the strong interaction of the individual magnetic fields, the placement of the high strength magnets creating the Halbach array in the plate support structure proved to be the most challenging portion of the assembly. The magnets, each with its own angle of orientation, were fabricated at Arnold and assembled into the plates to ensure correct phasing to achieve the proper overall magnetic field orientation. They are positioned using precision custom designed tooling and held in place with suitable adhesives.
Understanding the interactions between magnetic fields is essential in designing the magnet array to achieve the desired magnetic field strength and orientation. The individual components are assembled and the initial testing to verify Dr. Post’s code predictions is about to begin. Upon completion of the prototype testing, LLNL and Arnold will continue to work together analyzing the results in order to commercialize this technology.
Today magnetic bearings are used, in limited quantities, in uninterruptible power supplies, such as flywheel energy storage systems, couplers, motors, compressors, generators, magnetic levitation transportation, and medical devices. Passive magnetic bearings have several advantages over electromagnetic bearings. For example, they do not require an external power source to run and have no active control circuits. Consequently, they are far more efficient to operate.