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The Role of Reluctance in PM Motors

Description: The international research community has lately focused efforts on interior permanent magnet (IPM) motors to produce a traction motor for hybrid electric vehicles (HEV). One of the beneficial features of this technology is the additional torque produced by reluctance. The objective of this report is to analytically describe the role that reluctance plays in permanent magnet (PM) motors, to explore ways to increase reluctance torque without sacrificing the torque produced by the PMs, and to compare three IPM configurations with respect to torque, power, amount of magnet material required (cost), and percentage of reluctance torque. Results of this study will be used to determine future research directions in utilizing reluctance to obtain maximum torque and power while using a minimum amount of magnet material.
Date: June 16, 2005
Creator: Otaduy, P.J.
Partner: UNT Libraries Government Documents Department

Fringe fields for the N channel permanent magnet array

Description: Analytical expressions are obtained for fringe field multipoles of an N channel permanent magnet quadrupole array. It is assumed that the system of magnetic wedges starts at some transverse (x, y) plane located at z = 0, and it continues to a magnet length z = l, where it stops. The iron yoke continues to z = {+-} {infinity}, but it will be shown that only a small overhang is actually required to maintain the quadrupole and translational symmetries. Recall the 2-d solution for the magnetic potential (H = {del}{phi}): {phi}{sub 2} = A [(x-x{sub i}){sup 2} - (y-y{sub i}){sub 2}], where A = -M{sub 0}/4b, M{sub 0} is the remnant field of the wedges, and (x{sub i}, y{sub i}) are the coordinates for the center of box (i). Boxes have dimensions 2b x 2b and alternate between vacuum fill (for beams) and magnetic wedge fill. The 2-d system looks like a portion of an infinite transverse lattice with periodicity lengthy = 4b in both the x and y directions. For the magnetic potential {phi}, the periodicity length is 2b.
Date: April 1, 1996
Creator: Lee, E.P.
Partner: UNT Libraries Government Documents Department

PPM focused X-band klystron development at the Stanford Linear Accelerator Center

Description: X-band klystrons capable of 50 MW and utilizing Periodic Permanent Magnet (PPM) focusing are undergoing design and fabrication at the Stanford Linear Accelerator Center (SLAC). The klystron development is part of an effort to realize components necessary for the construction of the Next Linear Collider (NLC). The first klystron to be tested this year has a 0.6 microK beam at 465 kV, a 5 cells traveling wave output structure and a predicted efficiency of 63%. A 465 kV, 190 A beam stick with 12 periods of PPM focusing has recently operated to verify the gun optics and transmission of the beam in the absence of rf bunching. Beam transmission greater than 99.8% has been measured. Design and simulation of the beam stick and klystron are discussed, along with performance of the beam stick under confined flow and shielded conditions.
Date: July 1, 1996
Creator: Sprehn, D.; Caryotakis, G.; Eppley, K. & Phillips, R.M.
Partner: UNT Libraries Government Documents Department

Correction magnets for the Fermilab Recycler Ring

Description: In the commissioning of the Fermilab Recycler ring the need for higher order corrector magnets in the regions near beam transfers was discovered. Three types of permanent magnet skew quadrupoles, and two types of permanent magnet sextupoles were designed and built. This paper describes the need for these magnets, the design, assembly, and magnetic measurements.
Date: May 27, 2003
Creator: al., James T Volk et
Partner: UNT Libraries Government Documents Department

A Machine Approach for Field Weakening of Permanent-Magnet Motors

Description: The commonly known technology of field weakening for permanent-magnet (PM) motors is achieved by controlling the direct-axis current component through an inverter, without using mechanical variation of the air gap, a new machine approach for field weakening of PM machines by direct control of air-gap fluxes is introduced. The demagnetization situation due to field weakening is not an issue with this new method. In fact, the PMs are strengthened at field weakening. The field-weakening ratio can reach 1O:1 or higher. This technology is particularly useful for the PM generators and electric vehicle drives.
Date: April 2, 2000
Creator: Hsu, J.S.
Partner: UNT Libraries Government Documents Department

Interior Permanent Magnet Reluctance Machine with Brushless Field Excitation

Description: In a conventional permanent magnet (PM) machine, the air-gap flux produced by the PM is fixed. It is difficult to enhance the air-gap flux density due to limitations of the PM in a series-magnetic circuit. However, the air-gap flux density can be weakened by using power electronic field weakening to the limit of demagnetization of the PMs. This paper presents the test results of controlling the PM air-gap flux density through the use of a stationary brushless excitation coil in a reluctance interior permanent magnet with brushless field excitation (RIPM-BFE) motor. Through the use of this technology the air-gap flux density can be either enhanced or weakened. There is no concern with demagnetizing the PMs during field weakening. The leakage flux of the excitation coil through the PMs is blocked. The prototype motor built on this principle confirms the concept of flux enhancement and weakening through the use of excitation coils.
Date: October 7, 2005
Creator: Wiles, R.H.
Partner: UNT Libraries Government Documents Department

Long-term stability of Alnico 5 and 8 magnets at 700 to 1200$sup 0$F

Description: Tests performed to determine the long-term stability of Alnico 5 and 8 magnets for use in permanent magnet in-core sodium flowmeters are described. The results of this experiment showed that two processes combine to affect magnetic stability of these magnets at temperatures above 700 deg F: loss of field strength with time, the rate of loss increasing with temperature, and partial recovery of the loss caused by a high-temperature stabilization. The conclusion is that for a given temperature the most stable performance will be obtained by balancing these iwo processes with an optimum stabilization procedure. This procedure has yet to be established. For 12,000-hr operation, the recommended maximum temperatures are 1000 deg F for Alnico 5 (< plus or minus 10% drift), and 1100 deg F for Alnico 8 (< plus or minus 15% drift). (auth)
Date: November 1, 1973
Creator: Forster, G.A.
Partner: UNT Libraries Government Documents Department

Development of Proof-of-Concept Units for the Advanced Medium-Sized Mobile Power Sources (AMMPS) Program

Description: The purpose of this report is to document the development of the proof-of-concept units within the Advanced Medium-sized Mobile Power Sources (AMMPS) program. The design used a small, lightweight diesel engine, a permanent magnet alternator, power electronics and digital controls as outlined in the philosophy detailed previously. One small proof-of-concept unit was completed and delivered to the military. The unit functioned well but was not optimized at the time of delivery to the military. A tremendous amount of experience was gained during this phase that can be used in the development of any follow-on AMMPS production systems. Lessons learned and recommendations for follow-on specifications are provided. The unit demonstrated that significant benefits are possible with the new design philosophy. Trade-offs will have to be made but many of the advantages appear to be within the technical grasp of the market.
Date: April 3, 2002
Creator: Andriulli, JB
Partner: UNT Libraries Government Documents Department

Crystallographic texture determinations from inverse susceptibility measurements

Description: Determination of the quantitative relationship between crystallographic texture and magnetic properties in advanced permanent magnets may be hampered by complex microstructures, which complicate methods that rely on diffraction, or by interparticulate interactions, which adversely affect methods based on magnetic remanence measurements. To this end, new techniques in the determination of texture of bulk permanent magnets are being explored to overcome these inherent experimental difficulties. The analysis of inverse paramagnetic susceptibility measurements constitutes a new method to investigate crystallographic texture. Such measurements also provide Curie temperature data, which is sensitive to chemical changes that may have occurred in the magnetic phase during processing. The mathematical formalism underlying the analysis of inverse susceptibility measurements is outlined, and is used to evaluate magnetic measurements taken from a series of Nd{sub 2}Fe{sub 14}B magnets that have been processed by different means, and thus contain different degrees of texture. While this method does provide qualitative information concerning the relative crystallographic alignment of magnet samples, it needs calibration to obtain an explicit value for a texture order parameter.
Date: October 1, 1996
Creator: Lewis, L.H. & Welch, D.O.
Partner: UNT Libraries Government Documents Department

Synchrotron tune adjustment by longitudinal motion of quadrupoles

Description: Adjustment of the tune of a synchrotron is generally accomplished by globally varying the strength of the quadrupoles, either in the main quadrupole bus or in a set of dedicated trim quadrupoles distributed around the ring. An alternate scheme for tune control involves varying the strengths of quadrupoles only within a local insert, thereby adjusting the phase advance across the insert to create a ``phase trombone``. In a synchrotron built of permanent magnets, such as the proposed Fermilab Recycler Ring, tune adjustment may also be accomplished by constructing a phase trombone in which the longitudinal position rather than the strength of a number of quadruples is adjusted. Design philosophies and performance for such phase trombones are presented.
Date: July 1, 1996
Creator: Bertche, K.J.
Partner: UNT Libraries Government Documents Department

Ambient-temperature passive magnetic bearings: Theory and design equations

Description: Research has been underway at the Lawrence Livermore National Laboratory to build a theoretical and experimental base for the design of ambient-temperature passive magnetic bearings for a variety of possible applications. in the approach taken the limitations imposed by Earnshaw`s theorem with respect to the stability of passive magnetic bearing systems employing axially symmetric permanent-magnet elements are overcome by employing special combinations of elements, as follows: Levitating and restoring forces are provided by combinations of permanent-magnet-excited elements chosen to provide positive stiffnesses (negative force derivatives) for selected displacements (i.e., those involving translations or angular displacement of the axis of rotation). As dictated by Eamshaw`s theorem, any bearing system thus constructed will be statically unstable for at least one of the remaining possible displacements. Stabilization against this displacement is accomplished by using periodic arrays (`Halbach arrays`) of permanent magnets to induce currents in close-packed inductively loaded circuits, thereby producing negative force derivatives stabilizing the system while in rotation. Disengaging mechanical elements stabilize the system when at rest and when below a low critical speed. The paper discusses theory and equations needed for the design of such systems.
Date: December 30, 1997
Creator: Post, R.F. & Ryutov, D.D.
Partner: UNT Libraries Government Documents Department

Procurement history of the hybrid undulator for the U-5 Beam Line at the National Synchrotron Light Source

Description: As part of a national multi-institutional Materials Research Group (MRG), Argonne National Laboratory had the responsibility, under a prime contract with the U.S. Department of Energy, of obtaining a Permanent Magnet Hybrid undulator to be used on the U5 Beam Line on the VUV Ring at the National Synchrotron Light Source (NSLS). The procurement involved determining the technical specifications of the device as well as developing an effective procedure for evaluation of the proposals. The conceptual design of the magnetic structure including all pertinent magnetic field properties was developed before the actual procurement process was initiated. In addition, complete calculations of the expected spectral properties of the undulator were performed which included the emittance properties of the VUV ring. The results from both analysis were essential in determining the expected performance of the device and the final choice of operating parameters.
Date: May 1, 1989
Creator: James, D.C.; Bader, S.D. & Viccaro, P.J.
Partner: UNT Libraries Government Documents Department

Fermilab R{ampersand}D program in medium energyelectron cooling

Description: Fermilab began an R & D program in medium energy electron cooling in April 1995 with the object of cooling 8 GeV antiprotons in a new 3.3 km permanent magnet storage ring (Recycler) to be built in the same tunnel as the Main Injector (MI). The MI is to be completed in 1998, and it is planned to install the Recycler by the end of 1997 to reduce interference during the final rush of MI installation. Although the Recycler will employ stochastic cooling initially, its potential for contributing an order of magnitude to Tevatron collider luminosity is tied to electron cooling. The short time scale and Fermilab`s limited familiarity with low energy electron beams has given rise to a two-phase development plan. The first phase is to build a cooling system based on an electron beam of {ge} 200 mA before year 2000. The second phase of about 3 years is planned to reach electron current of 2 A or more. This report describes the general scheme for high luminosity collider operation as well as the R & D plan and progress to date. 17 refs., 5 figs., 1 tab.
Date: July 1, 1996
Creator: MacLachlan, J.A.
Partner: UNT Libraries Government Documents Department

Hybrid permanent quadrupoles for the 8 GeV transfer line at Fermilab

Description: Hybrid Permanent Magnet Quadrupoles for specialized portions of the 8 GeV transfer line from the Fermilab Booster to the new Main Injector have been built, tested and installed. These magnets use a 0.635 m long iron shell and provide an integrated gradient of 1.48 T-m/m with an iron pole tip radius of 0.0416 m. and pole length of 0.508 m. Bricks of 0.0254 m thick strontium ferrite supply the flux to the back of the pole to produce the desired 2.91 T/m gradient. For temperature compensation, Ni-Fe alloy strips are interspersed between ferrite bricks to subtract flux in a temperature dependent fashion. Adjustments of the permeance of each pole using iron from between the pole and the flux return shell permits the matching of pole potentials. Magnetic potentials of the poles are measured with a Rogowski coil and adjusted to the desired value to achieve the prescribed strength and field uniformity. After these adjustments, the magnets are measured using a rotating coil to determine the integral gradient and the harmonics. These measurements are used to calibrate the production Rogowski coil measurements. Similar quadrupoles are included in the design of the Fermilab Recycler.
Date: June 1, 1997
Creator: Pruss, S. M.; Foster, G. W.; Glass, H. D.; Harding, D. J.; Jackson, G. P.; May, M. P. et al.
Partner: UNT Libraries Government Documents Department

Status report of a compact 10 GHz electron cyclotron resonance (ECR) ion source for atomic physics experiments

Description: A summary of recent modifications and developments of a compact, fully permanent magnet ECR ion source will be given in this paper. To improve the confinement of the plasma electrons the axial magnetic mirror ratio has been enhanced to 2.5. This results in a more efficient plasma heating at low microwave power levels and therefore ion currents up to 320 e{mu}A could be extracted with a microwave power of less than 10 Watts. The maximum intensities for different charge states and various gases obtained so far will be shown.
Date: August 1, 1997
Creator: Trassl, R.; Broetz, F. & Pawlowsky, M.
Partner: UNT Libraries Government Documents Department

Results from a prototype permanent magnet dipole-quadrupole hybrid for the PEP-II B-factory

Description: We describe the construction of a prototype hybrid permanent magnet dipole and quadrupole. The magnet consists of two concentric rings of Sm{sub 2}Co{sub 17} magnetic material 5 cm in length. The outer ring is made of 16 uniformly magnetized blocks assembled as a Halbach dipole and the inner ring has 32 blocks oriented in a similar fashion so as to generate a quadrupole field. The resultant superimposed field is an offset quadrupole field which allows us to center the field on the high-energy beam in the interaction region of the PEP-II B-factory. The dipole blocks are glued to the inside surface of an outer support collar and the quadrupole blocks are held in a fixture that allows radial adjustment of the blocks prior to potting the entire assembly with epoxy. An extensive computer model of the magnet has been made and from this model we developed a tuning algorithm that allowed us to greatly reduce the n=3 17 harmonics of the magnet.
Date: June 1, 1997
Creator: Sullivan, M.; Bowden, G. & Ecklund, S.
Partner: UNT Libraries Government Documents Department

Inductrack demonstration model

Description: A small-scale model track of a new type of magnetic levitation system (dubbed the ``Inductrack`` system), and a passively magnetically levitated cart, has been designed, constructed and operated. The track consists of a close-packed array of rectangular levitation coils, 15 centimeters in width transversely and 20 meters in length. The array of coils is inductively loaded above and below its lower horizontal section with ferrite tiles. Paralleling the levitation coils on each side are aluminum-channel rails on which ride auxiliary wheels attached to the cart. The cart has, on its lower surface and on its sides, fore and aft, special arrays (``Halbach arrays``) of permanent magnet bars that produce a strong periodic magnetic field below the cart. This magnetic field, when the cart is in motion, induces repelling currents in the Inductrack coils, levitating it and centering it transversely. When mechanically launched (with a pulley- and-weight system) at speeds substantially above a ``transition speed`` of about 2 meters per second, the cart levitated and flew stably down the track, settling to rest on its wheels near the end of the track. In the last phase of the program an electromagnetic launching section consisting of another array of coils, connected to pulse-driver circuits, was added at the beginning of the track. Aided by an initial launch (from stretched ``bungee`` cords), this electromagnetic launching system was operated successfully, resulting again in levitation and subsequent stable flight of the cart.
Date: February 3, 1998
Creator: Post, R.F.
Partner: UNT Libraries Government Documents Department

Effect of permanent-magnet irregularities in levitation force measurements.

Description: In the measurement of the levitation force between a vertically magnetized permanent magnet (PM) and a bulk high-temperature superconductor (HTS), PM domains with horizontal components of magnetization are shown to produce a nonnegligible contribution to the levitation force in most systems. Such domains are typically found in all PMs, even in those that exhibit zero net horizontal magnetic moment. Extension of this analysis leads to an HTS analog of Earnshaw's theorem, in which at the field-cooling position the vertical stiffness is equal to the sum of the horizontal stiffnesses, independent of angular distribution of magnetic moments within the PM.
Date: October 14, 1999
Creator: Hull, J. R.
Partner: UNT Libraries Government Documents Department


Description: The recent upgrade of the NSLS X-Ray Ring energy from 2.584 to 2.8 GeV requires defocusing sextupole fields beyond the operating limits of the present sextupole magnets. We have demonstrated that the required fields can be achieved by addition of permanent magnets to counteract the saturation in the magnet poles. Magnetic measurements on a NSLS sextupole agree with fields predicted by Radia.
Date: June 18, 2001
Creator: RAKOWSKY,G.
Partner: UNT Libraries Government Documents Department

Adjustable permanent quadrupoles for the next linear collider

Description: The proposed Next Linear Collider (NLC) will require over 1400 adjustable quadrupoles between the main linacs' accelerator structures. These 12.7 mm bore quadrupoles will have a range of integrated strength from 0.6 to 138 Tesla, with a maximum gradient of 141 Tesla per meter, an adjustment range of +0 to {minus}20% and effective lengths from 324 mm to 972 mm. The magnetic center must remain stable to within 1 micron during the 20% adjustment. In an effort to reduce costs and increase reliability, several designs using hybrid permanent magnets have been developed. Four different prototypes have been built. All magnets have iron poles and use Samarium Cobalt to provide the magnetic fields. Two use rotating permanent magnetic material to vary the gradient, one uses a sliding shunt to vary the gradient and the fourth uses counter rotating magnets. Preliminary data on gradient strength, temperature stability, and magnetic center position stability are presented. These data are compared to an equivalent electromagnetic prototype.
Date: June 22, 2001
Creator: al., James T. Volk et
Partner: UNT Libraries Government Documents Department

Adjustable Permanent Quadrupoles Using Rotating Magnet Material Rods for the Next Linear Collider

Description: The proposed Next Linear Collider (NLC) will require over 1400 adjustable quadrupoles between the main linacs' accelerator structures. These 12.7 mm bore quadrupoles will have a range of integrated strength from 0.6 to 132 Tesla, with a maximum gradient of 135 Tesla per meter, an adjustment range of +0-20% and effective lengths from 324 mm to 972 mm. The magnetic center must remain stable to within 1 micrometer during the 20% adjustment. In an effort to reduce estimated costs and increase reliability, several designs using hybrid permanent magnets have been developed. All magnets have iron poles and use either Samarium Cobalt or Neodymium Iron to provide the magnetic fields. Two prototypes use rotating rods containing permanent magnetic material to vary the gradient. Gradient changes of 20% and center shifts of less than 20 microns have been measured. These data are compared to an equivalent electromagnet prototype.
Date: September 24, 2001
Creator: al., James T Volk et
Partner: UNT Libraries Government Documents Department

Multilevel DC Link Inverter for Brushless Permanent Magnet Motors with Very Low Inductance

Description: Due to their long effective air gaps, permanent magnet motors tend to have low inductance. The use of ironless stator structure in present high power PM motors (several tens of kWs) reduces the inductance even further (&lt; 100 {micro}H). This low inductance imposes stringent current regulation demands for the inverter to obtain acceptable current ripple. An analysis of the current ripple for these low inductance brushless PM motors shows that a standard inverter with the most commonly used IGBT switching devices cannot meet the current regulation demands and will produce unacceptable current ripples due to the IGBT's limited switching frequency. This paper introduces a new multilevel dc link inverter, which can dramatically reduce the current ripple for brushless PM motor drives. The operating principle and design guidelines are included.
Date: October 29, 2001
Creator: Su, G. J.
Partner: UNT Libraries Government Documents Department

Time evolution of fields in strontium ferrite permanent magnets

Description: Field strengths for strontium ferrite permanent magnets built for the Fermilab Recycler and 8 GeV transfer line have been measured for the past 4 years. The ferrite magnetization exhibits a time dependence parameterized by M1/M{sub 2} = -9 x 10{sup -4} x log (t{sub 1}/t{sub 2}) as determined from measurements of a gradient magnet. This parameterization has been checked against several other styles of permanent dipoles, and quadrupole magnets with good agreement.
Date: June 11, 2001
Creator: al., James T. Volk et
Partner: UNT Libraries Government Documents Department