Transverse Flux Linear Machine Research Articles

Electromagnetic Design and Analysis of a Stator–Magnet Transverse Flux Linear Oscillatory Machine with Yokeless Mover Core

Conventional stator–magnet moving−iron transverse−flux linear oscillatory machines (CSMTLOMs) are widely applied in directly−drive reciprocating devices due to the merits of easy fabrication and robust mover. However, in order to keep the mover vibrating at a certain resonance frequency to save the energy and enlarge the output power, they still suffer from a higher requirement on spring stiffness due to their thick and heavy mover core, which would also narrow the frequency band with a high power factor due to the large inertial energy storage of the heavy mover. Hence, to reduce the mover core weight to reduce the demand of the spring and improve the operation performance, an improved linear oscillatory machine featured by a spoke−type interior permanent magnet inner stator (ISMTLOM) is proposed. Benefiting from its separated two stators, the tangential flux in the radial plane can return through the inner stator core, so that the yoke of the mover core can be eliminated directly. Then, to analytically investigate the influence of the special axial local saturation effect, the segmental equivalent magnetic circuit (EMC) model of the ISMTLOM is established, wherein a saturation coefficient is introduced to quantitatively consider the local saturation effect on the output force. Consequently, several important size parameters are optimally selected when keeping the same outer diameter and copper loss as that of the CSMTLOM. Afterward, the three−dimension finite element algorithm (3D FEA) is adopted for the electromagnetic performance validation and comparison. Finally, it is found that the nonlinear segmental EMC corrected by the saturation coefficient can quickly predict the output force more accurately within the wide load range, and benefiting from the topology improvement, the ISMTLOM has the merits over the CSMTLOM in its smoother output force, much lighter mover core, and less demand of mechanical spring stiffness, whilst preserving the similar output force density.

A novel tubular High-Power-Factor Transverse-Flux linear machine with Concentrated-Flux teeth

Due to principle constraints of the conventional transverse flux permanent magnet linear machine, its PM utilization is less than half. Besides, the complex structure and the serious magnetic leakage also lead to the limited thrust increase and the sharp decline of power factor. Therefore, the high-power-factor transverse-flux permanent-magnet linear machine (HPF-TFPMLM) using the concentrated-flux teeth is proposed in this paper. First, the topology and operation principle of the circumferentially distributed HPF-TFPMLM are investigated. The concentrated-flux teeth and multi-unit concentrated windings are introduced to improve power factor of the HPF-TFPMLM. To further study the proposed HPF-TFPMLM, its counterpart of the axial distributed topology is proposed for comparative analysis. Then, the key electromagnetic performance of power factor, thrust and thrust density of the HPF-TFPMLM are analyzed. Its performances including no-load EMF, magnetic field distribution and overload capacity are evaluated and compared with its counterpart. Finally, the feasibility and correctness of the investigated HPF-TFPMLM are verified.

Design and Analysis of a Novel Tubular High-PM-Utilization Transverse-Flux Linear Machine

Owing to the low permanent magnet (PM) utilization in conventional transverse-flux machines, a novel tubular high-PM-utilization transverse-flux linear machine (HPMU-TFLM) is proposed in this article. The PM utilization ratio of the proposed machine is nearly 100% in theory. Thus, this machine presents a higher power factor and thrust density. First, the basic structure and operation principle of HPMU-TFLM are introduced. The flux-concentrating teeth and multi-unit concentrated winding are designed to improve PM utilization and reduce magnetic flux leakage. Then, the electromagnetic performances of HPMU-TFLM are investigated by the 3-D equivalent magnetic circuit model (EMCM) and the finite element analysis (FEA) method. Finally, its key performances of thrust density, power factor, and efficiency are compared with other typical transverse-flux linear machines (TFLMs). The superiority and feasibility of the proposed machine are verified.

Development, Design, and Analysis of a Dual-Consequent-Pole Transverse Flux Linear Machine for Direct-Drive Applications

Transverse flux machines can achieve high force density by reducing the pole pitch because of the decoupling of electric and magnetic loadings. But the main flux linkage interlinking with the armature coils will decrease as the pole pitch reduces, resulting in motor performance degradation. Unlike the approaches adopted by many literatures to suppress the leakage flux, this article proposes a novel dual-consequent-pole transverse flux linear machine by adopting dual-PM structure. Without increasing the occupied volume, the coil flux linkage is enhanced and the force density can be further improved. At first, the basic configuration and operation principle are introduced at first. Then the leading parameter influence on the force density is investigated. The electromagnetic performance of the proposed machine is investigated by three-dimensional finite element analysis and is compared with its counterparts. The field distribution, winding flux linkage, back electromotive force, detent force, and thrust force are emphasized as well as the efficiency and power factor. Finally, a prototype machine is constructed and tested to validate the theoretical analysis.

Development of a Novel Transverse Flux Tubular Linear Machine With Parallel and Complementary PM Magnetic Circuit for Precision Industrial Processing

The transverse flux permanent-magnet (PM) linear machine has attracted much attention in high-performance direct-drive applications because of its high torque density and efficiency. However, due to its inherent large open-circuit flux leakage, the prominent cogging force makes it difficult to obtain a high accuracy in position and speed control, which restricts its potential for precision industrial processing applications. To overcome this problem, a novel transverse flux linear machine is proposed in this paper. The key is by creatively combining a consequent-pole mover design and a stator-segment-interlacing configuration in such a way that a parallel and complementary transverse magnetic circuit is realized for the moving PMs, which can effectively minimize the open-circuit leakage flux and cogging effect. In this paper, the machine structure, operation principle, and theoretical modeling are introduced, with its electromagnetic performance evaluated by using the finite-element method. A prototype is also built for the experimental verification, and relevant test results agree well with the finite-element predications.

Study of the assembly, build and test of a linear transverse flux machine

This study discusses the topology development of a cylindrical transverse flux linear machine for use with a free piston engine. Despite its three-dimensional flux path, the stator of this topology can be made from regular laminated components and only the translator includes soft magnetic composites. The detailed design development is discussed, including stator tooth combination, alternative winding, and fabrication techniques. Results from both finite element analysis and experimental measurement are compared, which gives a validation of the feasibility of the building process.

A Linear Laminated Cylindrical Transverse Flux Machine for Use With a Free Piston Engine

This paper discusses the development of a new topology of cylindrical transverse flux linear machine for use with a free piston engine. Despite its three-dimensional flux path, the stator of this topology can be made from regular laminated components and only the translator includes soft magnetic composites. The design development is discussed, including alternative winding and fabrication techniques. Finite element analysis, results of a laboratory prototype, and numerical-reluctance analysis are all used to give insight into the machine characteristics. By using flux and flux linkage factors, the tradeoff between force requirement and power factor is explored. It is shown that the power factor of this topology will generally vary from 0.89 to 0.6, which compares well with other transverse flux machines.

Design Considerations of Tubular Transverse Flux Linear Machines for Electromagnetic Launch Applications

Due to the achievable high force densities, permanent magnet linear machines with transverse flux configurations are gaining increased interest in electromagnetic launch (EML) applications, in which the force density demand is crucial. This paper deals with the design of a tubular transverse flux linear machine (TFLM) targeting EML applications, and the issues pertinent to its topology selection, design optimization, and thermal modeling are discussed. By overall comparison of practical topologies and technologies of the TFLM, a tubular moving-magnet topology with separated flux paths is believed to be more appropriate. Design optimization is then performed to maximize the thrust force under specific volumetric constraints. It is shown that the thrust force is more sensitive to the stator segment length, instead of the magnet thickness. Regarding the overload requirement inherent in EML systems, special focus is given on the thermal characteristics of the TFLM at overload conditions, and it is proved that the machine shows appreciable overload capability. Measurements carried out on a prototype TFLM have validated the predictions.

Coordinated Control of an Independent Multi-phase Permanent Magnet-type Transverse Flux Linear Machine Based on Magnetic Levitation

This paper proposes a coordinated control for an independent multi-phase transverse flux linear synchronous motor (IM-TFLSM) based on magnetic levitation. The stator structures of the IM-TFLSM are composed of a two set, which has independent three-phase windings and a double-sided air-gap as opposed to the conventional Y-connected three-phase linear motors. A suitable control algorithm is necessary to operate the applied linear machine. This study proposes a coordinated control algorithm for adjusting the mover air-gap and thrust force of the IM-TFLSM in order to maintain air-gap and phase shifted current control of the independent 3-phase modules. In addition, the principle of operation and its special structures are described in detail and the validity and effectiveness of the control algorithm is verified through multiple experimental results.

Design and Analysis of a Novel Transverse-Flux Tubular Linear Machine With Gear-Shaped Teeth Structure

A transverse-flux tubular linear machine with novel gear-shaped teeth for high force density is proposed. The teeth can be formed by silicon steel laminations or permanent magnets for a tubular linear switched reluctance or tubular linear hybrid motor. With the unique improved teeth structure and short magnetic circulation paths, larger propulsion force output can be obtained with reduced mover weight and volume. Simulation based on finite element method (FEM) verifies the validity of the proposed machine design. The proposed machines are compared with other transverse-flux linear machines. Results show that the proposed tubular motors exhibit better output performance with a higher force-to-volume ratio.

Dynamic Characteristic Analysis Considering Core Losses in Transverse Flux Linear Machine With Solid Cores

This paper deals with a method for dynamic characteristic analysis considering core losses in transverse flux linear machines (TFLMs) with solid cores. This paper focuses on how to calculate the core losses of solid cores and how to apply the core losses to the dynamic simulation. The magnetic field characteristics, which are used for the core loss calculation and dynamic simulation, are calculated by using a 3-D equivalent magnetic circuit network analysis method. The accuracy of the proposed core loss calculation and dynamic simulation methods are examined by comparing the input currents of the dynamic simulation model with the measured input current of two TFLM prototypes.

On the feasible polygon classifications of linear switched reluctance machines

This paper provides a systematic guidance for linear switched reluctance machine design. By classifying the feasible polygons for desired machine operations, the physical size limits of either longitudinal or transverse flux linear machine poles and pole pitches can be determined. Also, with appropriate objective function selections, the constraints for associated machine optimization studies can be defined from the polygon boundaries. Comparison verifications are provided to show the adequacies and capabilities of the proposed algorithms.

Three-dimensional field and side-force design analyses of a transverse flux linear switched-reluctance machine

This paper is intended to investigate the electromagnetic flux distribution and side-force characteristics of a transverse flux linear switched-reluctance machine (TFLSRM) by three-dimensional finite element method. With the flux path perpendicular to its moving direction, results showed that the TFLSRM is quite suitable for high speed linear motion applications, due to the generated electromagnetic side-force which enhance the overall system guidance. From comparison analysis, conceptual design suggestions on the machine pole shapes will also be supplied.

Fast 3-D magnetic field analysis of transverse flux linear reluctance propulsion machine by Fourier projection method

This paper proposes a finite-element based Fourier projection method to analyze the magnetic field distribution for a transverse flux linear reluctance propulsion machine. Since the machine's moving direction is perpendicular to its magnetic flux plane, it is unavoidable to solve the finite element problem with a 3-D form. The proposed method can project the 3-D magnetostatic Poisson's equation into three simplified Helmholtz's equations to solve the system magnetic field distribution in an efficient way. Through this modeling, the force pulsation phenomena and the flip-flop effect revealed in the machine system can be investigated.

A generalized 3-D dynamic modelling for transverse flux homopolar linear machines based on statistical saliency-effect superposition method

This paper presents a prototype of a transverse flux homopolar linear machine system, along with a systematic and generalized 3-D approach which is capable of analyzing three kinds of these linear machines: the transverse flux linear induction machine; the homopolar linear synchronous machine; and the transverse flux linear reluctance machine; all in one compact mathematical model. A novel methodology which combines the state-space technique with the statistical saliency effect superposition method is proposed. With such a detailed and generalized modelling approach, the capability of analyzing the saliency effects induced by the distributed windings in practical linear machine systems is enhanced, and the representations of all the related linear machine system equations can be manipulated in compact matrix forms. Experimental verifications confirm that this comprehensive theoretical approach is a convenient and reliable mathematical basis for computer-aided analysis and design studies on linear machine systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>