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15 May 2003

Volume 93, Issue 10, pp. 5855-8792

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Study of internal permanent magnet rotor made of 0.6C–13Cr–Fe dual state magnetic material

Masahiro Mita, Masahiro Masuzawa, Noriyoshi Hirao, and Fumio Kimura

J. Appl. Phys. 93, 8769 (2003); http://dx.doi.org/10.1063/1.1556983 (3 pages) | Cited 1 time

Online Publication Date: 9 May 2003

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We have successfully developed an internal permanent magnet (IPM) rotor using dual state bulk magnetic material to increase usable magnetic flux dramatically. The most significant benefit of the IPM rotor is its mechanical reliability, because permanent magnets are inserted in slots of soft magnetic material. On the other hand, there is significant leakage flux between adjoining permanent magnets in the soft magnetic rotor core, reducing the usable magnetic flux flowing into the stator core. To solve this problem, we used a dual state magnetic material, 0.6C–13Cr–Fe alloy. This soft magnetic material could locally be changed into nonmagnetic material by localized heat treatment. By changing the material at leakage flux path into nonmagnetic, we can reduce the leakage flux, while keeping the rotor mechanically sound. By applying the dual state magnetic material to an experimental eight pole IPM rotor, the useful flux flowing in the stator core differs by 8% when compared to an all soft magnetic rotor core. © 2003 American Institute of Physics.
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84.50.+d Electric motors
75.50.Ww Permanent magnets
75.50.Bb Fe and its alloys

Modular permanent magnet brushless servo motors

J. D. Ede, K. Atallah, and D. Howe

J. Appl. Phys. 93, 8772 (2003); http://dx.doi.org/10.1063/1.1556984 (3 pages)

Online Publication Date: 9 May 2003

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This article discusses the suitability of modular permanent magnet brushless machines for applications where servo characteristics are key performance requirements. It is shown that among the large number of feasible combinations of slot number and pole number, optimum combinations exist, which exhibit good servo characteristics.© 2003 American Institute of Physics.
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84.50.+d Electric motors
07.07.Tw Servo and control equipment; robots

Magnetic force characteristics according to the variation of asymmetric overhang ratio in brushless direct current motor

Yon Do Chun, Shinji Wakao, and Ju Lee

J. Appl. Phys. 93, 8775 (2003); http://dx.doi.org/10.1063/1.1556985 (3 pages) | Cited 1 time

Online Publication Date: 9 May 2003

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As usual, brushless dc motor (BLDCM) has the overhang structure of which permanent magnet (PM) length is longer than the stator’s stack length. Specially, in case of asymmetric overhang, we have to pay attention to the choice of suitable overhang ratio of the lower to the upper overhang length because of the effect of the ratio on the magnetic forces. In this article, the magnetic force characteristics of BLDCM with the asymmetric overhang and the cap of the rotor are analyzed. A three-dimensional equivalent magnetic circuit network (EMCN) method is used for the efficient analysis of the magnetic field. The magnetic forces and torque are calculated by Maxwell’s stress tensor. The variation of magnetic force characteristics is also analyzed according to the overhang ratio. From the results, when the overhang ratio is 0.38, the axial magnetic force characteristic could be improved remarkably. The validity of the analysis results is also clarified by comparison between calculated results and measured ones. © 2003 American Institute of Physics.
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84.50.+d Electric motors
85.70.-w Magnetic devices

Performance analysis of a brushless dc motor due to magnetization distribution in a continuous ring magnet

Jin Hur, In-Soung Jung, Ha-Gyeong Sung, and Soon-Sup Park

J. Appl. Phys. 93, 8778 (2003); http://dx.doi.org/10.1063/1.1556986 (3 pages)

Online Publication Date: 9 May 2003

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This paper represents the force performance of a brushless dc motor with a continuous ring-type permanent magnet (PM), considering its magnetization patterns: trapezoidal, trapezoidal with dead zone, and unbalanced trapezoidal magnetization with dead zone. The radial force density in PM motor causes vibration, because vibration is induced the traveling force from the rotating PM acting on the stator. Magnetization distribution of the PM as well as the shape of the teeth determines the distribution of force density. In particular, the distribution has a three-dimensional (3-D) pattern because of overhang, that is, it is not uniform in axial direction. Thus, the analysis of radial force density required dynamic analysis considering the 3-D shape of the teeth and overhang. The results show that the force density as a source of vibration varies considerably depending on the overhang and magnetization distribution patterns. In addition, the validity of the developed method, coupled 3-D equivalent magnetic circuit network method, with driving circuit and motion equation, is confirmed by comparison of conventional method using 3D finite element method. © 2003 American Institute of Physics.
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84.50.+d Electric motors
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
84.30.Bv Circuit theory
02.70.Dh Finite-element and Galerkin methods

Modeling of switched reluctance motor using Fourier series for performance analysis

Jin Hur, Chong-Chul Kim, and Dong-Seok Hyun

J. Appl. Phys. 93, 8781 (2003); http://dx.doi.org/10.1063/1.1556987 (3 pages) | Cited 1 time

Online Publication Date: 9 May 2003

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A computational method for a performance analysis of the switched reluctance motor has been developed. Most of the papers present static characteristics, such as static torque based on a finite element method analysis. However, this method is based on a Fourier series expansion with step-by-step, current-dependent, adjustable coefficients. Analytical expression for the calculation of instantaneous phase inductance, flux linkage, co-energy, and electromagnetic torque as a function of rotor position and winding current are derived. Finally, the strategy to represent the winding inductance variation with position is made by approximating the actual inductance profile. © 2003 American Institute of Physics.
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84.50.+d Electric motors
02.70.Dh Finite-element and Galerkin methods

Detent torque from the soft magnetic stator stack of a hybrid stepper motor

K. R. Rajagopal, Bhim Singh, and B. P. Singh

J. Appl. Phys. 93, 8784 (2003); http://dx.doi.org/10.1063/1.1556988 (3 pages)

Online Publication Date: 9 May 2003

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The residual magnetism present in the stator stack of a hybrid stepper motor, which will be of the last excited polarity, will develop a detent torque, similar to the static torque of the last excited phase, but with reduced excitation. The predominant component is fundamental. Even though this torque is the result of the stator excitation, it can be considered as a detent torque as it is available when the stator excitation is withdrawn. This detent torque is in addition to the inherent one due to the rotor permanent magnet, and it will be present until the next phase is switched ON. Once the excitation is removed from the second phase, because of the hysteresis the detent torque will be available, similar to the static torque profile for phase 2, but with less excitation. This means because of the hysteresis the detent torque follows the static torque of the phases. The magnitude of this detent torque will depend upon the level to which the phase was excited. Experiments have been carried out on a 0.5° hybrid stepper motor to study the effects of the excitation on the detent torque profiles. Harmonic analyses of the measured detent torque curves had been carried out and it is seen that the fundamental detent torque increases with the excitation and also follows the respective phases. Therefore, the residual flux density and the coercive force of the soft magnetic material used for the stator stack have to be as small as possible to get rid of this effect. Controlling a hybrid stepper motor by a suitable switching scheme for a given application requires the measured static torque profiles of the motor for all the phases at the exact working voltage (or voltages in case of a variable voltage supply) and detent torque profiles both before and after excitation. Harmonic spectrum of the measured static and detent torque profiles have to be accounted for while simulating stepping behavior of the motor, from which an appropriate switching scheme can be arrived at. © 2003 American Institute of Physics.
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84.50.+d Electric motors
75.00.00 Magnetic properties and materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects

Dynamic modeling of tubular moving-magnet linear actuators

R. E. Clark, G. W. Jewell, and D. Howe

J. Appl. Phys. 93, 8787 (2003); http://dx.doi.org/10.1063/1.1544518 (3 pages) | Cited 3 times

Online Publication Date: 9 May 2003

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This article examines the influence of eddy currents on the dynamic performance and efficiency of a small reciprocating permanent magnet actuator for use in air compressors. Transient finite element simulations are compared with results from magnetostatic analyses and measurements. It is shown that induced eddy currents reduce the efficiency by ∼5%. The influence of the excitation current wave form on the eddy current loss and the actuator efficiency is also examined. © 2003 American Institute of Physics.
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85.70.Rp Magnetic levitation, propulsion and control devices
85.70.Ay Magnetic device characterization, design, and modeling
75.50.Ww Permanent magnets
07.55.Db Generation of magnetic fields; magnets
02.70.Dh Finite-element and Galerkin methods

Flux measurements and modeling of the magnetic hysteresis for a zero-voltage switching dc-to-dc converter

H. Hauser, F. Himmelstoss, and P. Wurm

J. Appl. Phys. 93, 8790 (2003); http://dx.doi.org/10.1063/1.1555318 (3 pages) | Cited 3 times

Online Publication Date: 9 May 2003

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A half-bridge bidirectional step-up dc/dc converter with zero voltage switching is introduced. The losses in the semiconductors are reduced in this concept but the higher current ripple leads to increased losses in the MnZn ferrite inductor. The resulting unsymmetric hysteresis including minor loops due to switching oscillations is predicted using reversible and irreversible energy contributions. © 2003 American Institute of Physics.
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84.30.Jc Power electronics; power supply circuits
84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables
41.20.Gz Magnetostatics; magnetic shielding, magnetic induction, boundary-value problems
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