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Applications of High Performance Permanent Magnets

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This is a presentation for the 20th Workshop on Rare Earth Permanent Magnets and Applications (REPM08) , September 8-10, 2008, Crete, Greece

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Applications of High Performance Permanent Magnets

  1. 1. Applications of High Performance Permanent Magnets J. F. Liu Electron Energy Corporation 924 Links Ave, Landisville, PA 17538, USA Phone: 1-717-898-2294 Fax: 1-717-898-0660
  2. 2. <ul><li>Some Magnet Design Considerations </li></ul><ul><li>Permanent Magnet Dipoles </li></ul><ul><li>Permanent Magnet Quadrupoles </li></ul><ul><li>Magnetic Mangles </li></ul><ul><li>Magnetic Couplings </li></ul><ul><li>High temperature hybrid magnetic bearings </li></ul><ul><li>Summary </li></ul>Outline
  3. 3. Permeance Coefficient P c <ul><li>Also known as load line or operating point </li></ul><ul><li>It is related to the dimensions of the magnets and the associated magnetic circuit </li></ul>In the magnetic circuit, a magnet will operate at a specific point on its extrinsic demagnetization curve: P c =B d /H d Some Magnet Design Considerations P c = B d /H d B r B d H d H c
  4. 4. Why straight-line demagnetization curves? Application with load line #1: Both magnets are okay to use Application with load line #2: Only magnet #1 is suitable B d1 Normal demagnetization curve for magnet #1 load line 2 B r H c 0 Knee load line 1 B d2 H d1 H d2 B r H c Normal demagnetization curve for magnet #2
  5. 5. Permanent Magnet Dipoles Halbach PM Dipole Structures: B g = B r ln(OD/ID) <ul><li>There is no upper limit for air gap flux density in Halbach dipole structures according to above equation. But in reality it would be limited by: </li></ul><ul><li>The realistic size </li></ul><ul><li>The demagnetization effect </li></ul>OD ID
  6. 6. Vector Map Flux Density Map Halbach Dipole Structure
  7. 7. <ul><li>4 Tesla PM prototype Halbach cylinder was prototyped in Japan.* </li></ul><ul><li>EEC has produced many small Halbach structures for a variety of applications. </li></ul><ul><li>Sintered Sm-Co or high H ci Nd-Fe-B magnets are good choices </li></ul>*M. Kumada et al, PAC2001, 3221 . Halbach Dipole Structure
  8. 8. A Example of Halbach PM Quadrupole
  9. 9. Magnetic Mangles 45 o Position 90 o Position 135 o Position 0 o Position
  10. 10. <ul><li>Adjustable magnetic quadrupoles as reported by Fermi lab and SLAC*: </li></ul><ul><li>Diametrically magnetized SmCo 2:17 tuning rods </li></ul><ul><li>Tuning rods rotation changes the strength of field gradient </li></ul>* J. T. Volk et al, PAC2001, p217 Adjustable Magnetic Quadrupoles
  11. 11. Surface Coupler with 12 Alternating Poles Flux density along the center line of the air gap Flux in Tesla
  12. 12. Concentric Coupling System Applications include mixers and pumps, especially for pharmaceutical, chemical and medical applications.
  13. 13. Solid Model of the Radial Bearing Actual Radial Bearing High Temperature PM Biased Magnetic Bearings Supported by NASA Glenn Research Center, EEC/TAMU designed and built a PM-biased hybrid high temperature magnetic bearing that can operate at 1000 F Back Iron Pieces Permanent Magnets Dual Lamination Stacks Rotor Lamination Stack Small Air Gap
  14. 14. High temp magnet arc segments assembled together. Magnet arc assemblies stuck in place on outer diameter of bearing lamination stacks. Magnet Demagnetization Curves of T550 High temp magnet High Temperature PM Biased Magnetic Bearings
  15. 15. Flux Contours from EM FEA with PM bias and control flux. High Temperature PM Biased Magnetic Bearings
  16. 16. Design parameters <ul><li>Bias flux subtracted from total gap flux. </li></ul><ul><li>At 22°C, FEA Bias Flux Density = 0.98 T, At 550°C, it’s 0.53 T. </li></ul><ul><li>540 Amp-Turns will not be sufficient to completely drive gap flux density to zero. </li></ul>PM-Biased Radial Bearing Design Details Control Flux Density as a function of Amp-Turns 15 11.25 7.5 3.75 0 Amps 0.50 0.42 540 0.45 0.37 405 0.40 0.31 270 0.23 0.20 135 0.00 0.00 0 22°C 550°C Average Gap Control Flux (TESLA) Amp-Turns 0.98 T Air Gap Flux at 22 o C 2910 N Linear Load Capacity 0.53 T Air Gap Flux at 550°C 208 N Bearing Weight 8.18 cm Bearing Length 23.75 cm Bearing OD New Design Parameter
  17. 17. Radial Bearing Test Apparatus
  18. 18. <ul><li>Negative position stiffness (nps)– measured radial bearing force vs. rotor position. </li></ul><ul><li>Test performed with zero control current. </li></ul><ul><li>nps = 13.3 kN/mm (76 lb/mil). </li></ul><ul><li>All 12 poles on two stators energized to determine max. possible current stiffness (cs). </li></ul><ul><li>Rotor held as best as possible in geometric center position. </li></ul><ul><li>cs = 233 N/A (52 lb/A). </li></ul>Some Room Temperature Results from Radial Bearing Bench Tests Force vs. Rotor Position Force vs. Control Current
  19. 19. A Comparison of Analytical and Experimental Room Temperature Radial Bearing Test Results Radial Bearing Force vs. Current at R.T. <ul><li>Reasonably good agreement between 3D FEA and 4 Load Cell Data. </li></ul><ul><li>Analytical result at 10 Amps is 7% higher than actual </li></ul>
  20. 20. Some High Temperature Results from Radial Bearing Bench Tests <ul><li>Test temperatures: PM’s were 493°C, Shaft was 350°C, Ceramic Layer on Poles was 366°C. </li></ul><ul><li>Max. Force Output: Force at 13.3 amps with centered rotor was 2800 N (629 lbs), which is 86% of RT result. </li></ul><ul><li>Max. Position-related force: 2220 N at 0.38 mm rotor offset. Yields approximate nps = 5.8 kN/mm, which is about 44% of RT result. </li></ul><ul><li>SmCo magnets and control coils works very well at elevated temperatures. </li></ul>
  21. 21. Solid Model of High Temperature Test Rig Components We are in a process of building this test rig. It will be ready later this year.
  22. 22. Summary A new hybrid high-temp magnetic bearing was designed and built using high temperature Sm-Co magnets. It will be tested using a specially design test rig Permeance Coefficient of magnets in the electromechanical system should be carefully considered in the design and material selection stage Halbach principles can be used in many different applications

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