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Magnetic lead screw (MLS) is a new type of high performance linear actuator that is attractive for many potential applications. The main difficulty of the MLS technology lies in the manufacturing of its complicated helical-shape magnetic poles. Structure simplification is, therefore, quite essential in promoting the MLS technology. In this paper, a new approach is proposed for forming the required helical-shape magnetic poles in a much simpler way. It is demonstrated that the traditional ring-shape magnetic poles, by proper rotating or shaping, can well approximate the complicated helical-shape magnetic poles. The performance of the new structure is compared with a MLS with ideal helical-shape magnetic poles using 3-D finite-element analysis. Halbach and flux concentration designs using the new approach are introduced. [ABSTRACT FROM AUTHOR]

This paper presents a new transverse flux permanent magnet machine. In a normal transverse flux machine, complicated 3-D flux paths often exist. Such 3-D flux paths would require the use of soft magnetic composites material instead of laminations for construction of the machine stator. In the new machine topology proposed in this paper, by advantageously utilizing the magnetic flux path provided by an additional rotor, use of laminations that allow 2-D flux paths only will be sufficient to accomplish the required 3-D flux paths. The machine also has a high torque density and is therefore an attractive solution for various direct drive applications. [ABSTRACT FROM PUBLISHER]

This paper presents a new type electromagnetic lead screw (EMLS) intended for wave energy application. Similar to the mechanical lead screw, this electromagnetic version can transfer slow linear motion to high-rotational motion, offering gearing effects. Compared with the existing pure magnetic lead screw (MLS) employing permanent magnets only, the new EMLS proposed uses dc current to provide the required helical-shape magnetic field, offering a much simpler, robust structure compared with the MLS. The working principle and the performances of this EMLS are analyzed in this paper. Comparison with PM-type lead screw is given. In addition to this, the theoretical analysis to support the use of a 2-D finite element model to analyze the 3-D magnetic-type lead screw is given, which has not been well covered in the existing literature. [ABSTRACT FROM AUTHOR]

In this paper, a new motor integrated permanent magnet gear (MIPMG) is discussed. The focus is on eddy current loss analysis associated to permanent magnets (PMs). A convenient model of MIPMG is provided based on 2-D field-motion coupled time-stepping finite element method for transient eddy current analysis. The model takes the eddy current effect of PMs into account in determination of the magnetic field in the air-gap and in the magnet regions. The eddy current losses generated in the magnets are properly interpreted. Design improvements for reducing the eddy current losses are suggested. The proposed model and the results presented in this paper will give useful guidelines for a reliable design and design optimization of the MIPMG. [ABSTRACT FROM PUBLISHER]

This paper presents a new single-phase, Hybrid Switched Reluctance (HSR) motor for low-cost, low-power, pump or fan drive systems. Its single-phase configuration allows use of a simple converter to reduce the system cost. Cheap ferrite magnets are used and arranged in a special flux concentration manner to increase effectively the torque density and efficiency of this machine. The efficiency of this machine is comparable to the efficiency of a traditional permanent magnet machine in the similar power range. The cogging torque, due to the existence of the permanent magnetic field, is beneficially used to reduce the torque ripple and enable self-starting of the machine. The starting torque of this machine is significantly improved by a slight extension of the stator pole-arc. A prototype machine and a complete drive system has been manufactured and tested. Results are given in this paper. [ABSTRACT FROM AUTHOR]

This paper presents a new method for computation of the nonlinear flux linkage in 3-D finite-element models (FEMs) of electrical machines. Accurate computation of the nonlinear flux linkage in 3-D FEM is not an easy task. Compared to the existing energy-perturbation method, the new technique introduced in this paper is much easier to use and is computational faster. This method is derived based on the “apparent energy.” Calculation of the nonlinear flux linkage from this energy avoids numerical differentiation, which is sensitive to numerical errors but is required in the traditional energy-perturbation method. The new method proposed is validated using experimental results on two different permanent magnet machines. [ABSTRACT FROM AUTHOR]

Permanent magnet transverse flux machine (PMTFM) is well known for its high torque density and is interested in various direct-drive applications. Due to its complicated 3-D flux components, design and design optimization of a PMTFM is more difficult and time consuming than for radial flux electrical machines. This paper addresses two important design considerations for PMTFM—the influence of permanent magnet leakage flux, which plays an important role in the determination of machine output torque, and the leakage inductance. A new simple method to provide a quick estimation of the armature leakage inductance is proposed, avoiding use of complicated 3-D equivalent reluctance network model to estimate the circumferential armature leakage flux component, and the pole face fringing flux component. Analysis results are supported by 2-D, and 3-D finite element (FE) analysis results, and measurement results on a prototype surface-mounted PMTFM. [ABSTRACT FROM AUTHOR]

The effects of saturation on torque production for non-salient, single-phase, permanent-magnet machines are studied in this paper. An analytical torque equation is proposed to predict the instantaneous torque with saturation effects. Compared to the existing methods, it is computationally faster and easier to calculate the torque using the analytical equation proposed. It can also handle arbitrary armature current waveforms and arbitrary flux linkage waveforms produced by the rotor permanent magnets. The results obtained by using the proposed torque equation are validated using finite-element results, and experimental results obtained on a prototype single-phase permanent-magnet machine. [ABSTRACT FROM AUTHOR]

Current-controlled variable inductors adjust the inductance of an alternating current (ac) coil by applying a controlled dc current to saturate the iron cores of the ac coil. The controlled dc current has to be maintained during operation, which results in increased power losses. This paper presents a new stress-based variable inductor to control inductance using the inverse magnetostrictive effect of a magnetostrictive material. The stress can be applied by a piezoelectrical material, and thus a voltage-controlled variable inductor can be realized with zero-power consumption. The new stress-based variable inductor concept is validated using a 3-D finite-element analysis. A prototype was manufactured, and the experimental results are presented. A linear relationship between inductance and applied stress can be achieved. [ABSTRACT FROM AUTHOR]

A typical giant magnetostrictive actuator (GMA) expands a magnetostrictive rod to generate strain by varying the current in the coil that surrounds the magnetostrictive rod. The heat generated by the current deteriorates the GMA performance. In particular, a constant current in the coil is required to produce the desired magnetic field when an output strain should be maintained. The GMA does not produce any mechanical power in this condition, but constant power is being consumed by the excitation coil. This paper presents a new type of motor-driven GMA (MDGMA), which works in a coil-free driven manner. The magnetic field in the iron–gallium alloy (Galfenol), which is a type of magnetostrictive material, is periodically altered by rotating the permanent magnets instead of varying the coil current in the traditional GMA. The proposed MDGMA not only achieves continuous adjustment of the output strain, but can also maintain a constant output strain without consuming any power. In addition, the coil-free design releases the new MDGMA from the heat generated by the excitation coil, which allows the MDGMA to work more stably. [ABSTRACT FROM AUTHOR]

The large normal force of a single-sided linear actuator may cause vibration, noise and reduce the positioning accuracy. To overcome these disadvantages, a new H-module linear actuator (HMLA) is proposed to reduce effectively the normal force without using expensive air suspension system or assisted guide. Compared to the existing HMLA, the teeth on the two opposite sides of the stator of this new HMLA are shifted by a tooth-shift-distance tsd. With a proper choice of tsd, the electromagnetic design and the force characteristics of the HMLA may be greatly improved. The finite element method (FEM) is employed to analyze the magnetic performance and the force characterization of an optimized HMLA with varying tsd. The performances when the HMLA is excited by rectangular and sinusoidal waveform currents are investigated. The result presented in this paper has shown that the total average tangential force of this new HMLA could be improved by 51% in comparison to the existing HMLA. [ABSTRACT FROM AUTHOR]

This paper presents an identification algorithm of the scalar Preisach model by using a set of symmetric minor hysteresis loops and suggests an improved vector Preisach model to describe the vector and anisotropic hysteresis behavior of a non-oriented (NO) electrical steel sheet (ESS) under rotating magnetic fields. Symmetric minor hysteresis loop is quite easy measured, so an identification algorithm based on symmetric minor hysteresis loop instead of first-order reverse curve is presented in this paper. The vector Preisach model employs a nonlinear coefficient, which is a function of magnitude and a direction of magnetic flux density, to describe the anisotropic property of the NO ESS and increases the numerical accuracy. The validity of the suggested vector Preisach model is investigated through comparisons with the experimental results under various magnetic field conditions. [ABSTRACT FROM AUTHOR]

This paper presents a new initial rotor position estimation method for an interior permanent magnet synchronous motor. The proposed method includes two steps. First, the minimum voltage vectors are injected to estimate the rotor position. Second, in order to identify the magnet polarity accurately, two opposite voltage pulses are injected on the estimated d-axis. In the proposed method, no filter is needed to draw the high frequency current signal for position estimation and no low-pass filter is required in the current control loop for extracting the fundamental current component for field-oriented control. The fast and reliable feature of this proposed method allows starting the motor with 100% load torque. The effectiveness of the proposed method is verified experimentally and the maximum position estimation error is around 6 electrical degrees. [ABSTRACT FROM AUTHOR]

In order to analyze the magnetic field distribution and thrust performance of the U-channel air-core permanent magnet linear synchronous motor (UAPMLSM), an analytical model is proposed based on the equivalent magnetization intensity method. The detailed analytical solutions of the magnetic flux density and thrust considering space harmonic components are derived, and then validated by the finite-element method results. With the provided analytical approach, it gives an insight into the key design parameters that may affect the characteristics of the magnetic field and thrust. The optimal design of the pole arc coefficient and coil span coefficient is given with minimized total harmonic flux density components and the thrust ripple. The proposed analytical model could be used for a quick and optimal design of the UAPMLSM. [ABSTRACT FROM AUTHOR]

In this paper, an effective cogging torque reduction method based on shifting the slot-openings is presented. Stator teeth are divided into groups and proper slot-opening shift is applied for each group. The cogging torque can then be greatly reduced while the back-EMF waveforms remain symmetrical. No additional back-EMF harmonic components will be introduced by this method. Analytical analysis revealing the working principle of this method is given, which gives a clear guide about how this method may be applied to different permanent magnet machines. [ABSTRACT FROM AUTHOR]

The single-sided linear actuator has usually large normal force which may induce large frictional force when using roll-bearings to support the linear motion. Otherwise, an air suspension system or assisted guide is needed to balance the normal force. A new H-module linear actuator (HMLA) with much lower normal force is proposed in this paper. The proposed new H-module linear actuator makes use of additional air suspension system unnecessary. The topology and working principle of the HMLA is illustrated in details in this paper. The force characteristics are analyzed by finite element method (FEM). The impacts of several key design parameters on the force characteristics are studied, and the HMLA is optimized afterwards. It is proved that the optimized HMLA could use less permanent magnet (PM) volume and generate larger useful tangential force and its normal force vs. tangential force ratio is much lower than that of the conventional single-sided linear actuator. [ABSTRACT FROM PUBLISHER]

In order to reduce the thrust ripple of linear servo system, a double-sided air core permanent magnet linear servo motor with trapezoidal shape permanent magnets (TDAPMLSM) is proposed in this paper. An analytical model of the motor for predicting the magnetic field in the air-gap at no-load is introduced. This model is derived based on the equivalent magnetization intensity method, and its accuracy is validated by using the results obtained from the finite-element method. The key dimensions that affect the air-gap magnetic field are analyzed based on the analytical model, and the design is optimized by using genetic algorithm. A thrust ripple reduction of 70.6% is achieved by optimization. The proposed analytical model may be used for a quick and reliable design and design optimization of the TDAPMLSM. [ABSTRACT FROM AUTHOR]