Transverse Flux Permanent Magnet Research Articles

Transverse flux permanent magnet generator design and optimization using response surface methodology applied in direct drive variable speed wind turbine system

Recently, Transverse Flux Permanent Magnet Generators (TFPMGs) have been proposed as a possible generator in direct drive variable speed wind turbines due to their unique merit. Generally, the quality of output power in these systems is lower than multi stage fixed speed systems, because of removing the gears, so it’s important to design these kinds of generators with low ripple and lowest harmful harmonics and cogging torque that is one of the most important terms in increasing the quality of output power of generator. The objective of this paper is introducing a simple design method and optimization of high power TFPMG applied in vertical axis direct drive wind turbine system by lowest possible amplitude of cogging torque and highest possible power factor, efficiency and power density. For this reason an optimum method called combined response surface methodology (RSM) and design of experiment and in order to extract the output values of generator and sensitivity analysis for design and optimization, 3D-Finite element model, was applied. This method has high accuracy and gives us a better insight of generator performance and presents back EMF, cogging torque, flux density and FFT of this TFPMG. This study can help designers in design approach of such generators.

A Gaussian process regression based on variable parameters fuzzy dominance genetic algorithm for B-TFPMM torque estimation

Transverse Flux Permanent Magnet Motor (TFPMM) has received extensive attention in the field of electric vehicles. The magnetic circuit of TFPMM is three-dimensional and non-linear, which leads to the high nonlinearity of electromagnetic torque. Although the three-dimensional finite element method (3DFEM) could be used to estimate torque, it is very time-consuming. Instead of it, this study adopts a kind of machine learning method—Gaussian process regression (GPR). For the hyper-parameters optimization of GPR, most previous studies used single-objective algorithms for improving the regression accuracy. However, GPR is an algorithm of probability prediction and it could not guarantee to have the satisfactory confidence interval characteristic simultaneously while the regression precision achieves optimal. Therefore this paper proposes a variable parameters fuzzy dominance genetic algorithm (VPFDGA) which is suitable for the multi-objective optimization, including the optimization of regression precision, confidence interval reliability, confidence interval width and skill score. By combining GPR with VPFDGA, the electromagnetic torque of a building-block transverse flux permanent magnet motor (B-TFPMM) is estimated by VPFDGA-GPR (GPR based on variable parameters fuzzy dominance genetic algorithm). Besides, two other GPRs based multi-objective optimization, three GPRs based on single-objective optimization and a GPR based on weighted sum method that is the classic multi-objective optimization algorithm are all implemented to compare with VPFDGA-GPR. The results of comparison show that VPFDGA-GPR has the better performances including the higher regression precision, more powerful ability of probability prediction, higher stability, less convergence time and so on.

Permanent magnet linear induction heating device: new topology enhancing performances

PurposeThis work aims to study a new design of linear permanent magnet transverse flux induction heating devices of nonmagnetic parallelepipedic workpiece. In these topologies, the permanent magnet inductor produces a static magnetic field, and the workpiece to be heated is subjected to a linear movement. To study the magnetothermal process, a new analytical coupling method between the magnetic and thermal phenomena is developed. This analytical model described in this study takes into account the variation of the physical properties of the heated workpiece. The analytical results are compared with good agreement to those issued from finite elements simulations, as well as those issued from measurements on an actual prototype.Design/methodology/approachThe research methodology is based on analytical development of coupled problem, including the electromagnetic and thermal boundary problems. A strongly coupled magneto-thermal analytical model is developed; the time dependent magnetic problem is first solved by using the separation of variables method to evaluate the induced currents in the nonmagnetic plate and the resulting power density loss distribution. The plate temperature profile is then obtained, thanks to strong involvement of this magnetic model in a new analytical thermal model based on a synergy of separation of variables method and Green’s function transient regime analysis method.FindingsThe results show that an efficient transient magneto-thermal analytical model was developed allowing fast analysis of permanent magnet induction heater for deep heating of parallelepipedic workpieces. Developed model allows also fast and precise simulations of nonlinear and transient magneto-thermal phenomena for different types of permanent magnet induction heating devices.Practical implicationsThe developed magneto-thermal analytical model can be used for fast designing of permanent magnet linear induction heating devices for moving parallelepipedic nonmagnetic workpiece.Originality/valueA new analytical coupled model, including the electromagnetic and transient thermal boundary problem with additional algebraic equations and taking into account the nonlinearity, has been developed. The developed model accuracy was validated with a permanent magnet linear induction heating device. Developed coupled analytical model allows fast analysis and designing of such permanent magnet linear induction heating devices.

Analysis of a transverse flux permanent magnet generator with fall-back outer rotor design for wind power generation

ABSTRACT The transverse-flux permanent-magnet generator (TFPMG) has been extensively employed in wind power applications. The distinct advantages of TFPMG over other types of generators are further enforced by important modifications in the form of fall-back inner rotor structure, half the permanent magnets, elliptical stator core and toroidal coils. Considering the benefits of natural cooling, along with the aforementioned modifications, the fall-back outer rotor TFPM design can offer further higher power-to-volume ratio. The topology of fall-back outer rotor TFPM machine is proposed, simulated and analysed in detail in this paper. The said machine design performance is compared with its conventional and inner rotor fall-back counterparts. The considerations of complexity, manufacturability, cost and performance results are encouraging.

Radially-Magnetized Transverse Flux Permanent Magnet Generator

The transverse flux permanent magnet motor attracts wide attention in the field of low-speed direct-drive wind power due to its high torque density, good low-speed performance and other advantages. Aiming at the problem of high leakage coefficient of permanent magnet in the attached transverse flux permanent magnet wind power generator, a radially-magnetized transverse flux permanent magnet generator (RM-TFPMG) is proposed in this paper. Details of the structure and principle of the proposed machine are introduced firstly, and then the main parameters of the RM-TFPMG are calculated by the magnetic circuit method. Finally, the three-dimensional finite element analysis of the radial load flux transverse flux permanent magnet generator is carried out by ANSYS Maxwell software, and the parameters of machine and Back Electromotive Force (EMF) are obtained under the condition of no-load, and the rationality of the designed motor is verified.

Thermal analysis and experimental verification of a staggered‐teeth transverse‐flux permanent‐magnet linear machine

To overcome the inherent demerit of low power factor existing in transverse-flux permanent-magnet (TFPM) machines, a tubular staggered-teeth TFPM linear machine is presented here. Linear alternator integrated with free-piston Stirling engines could offer a great potential in a wide variety of applications ranging from solar energy generation to space power supply. The thermal behaviour of the machine is studied using a three-terminal lumped-parameter thermal network (LPTN) to solve the problem of temperature overestimation of the traditional LPTN. The determination of thermal resistances and thermal parameters are introduced in detail. The temperatures of various components of the machine under different load conditions are calculated by both the three-terminal LPTN model and the numerical thermal model. Sensitivity analysis is carried out to study the influence of critical thermal parameters on the temperature rise of the machine. On this basis, the effectiveness of the forced air cooling is investigated. A prototype is fabricated and temperature experiment indicates that there is a good agreement between measurement and calculation.

A Novel Transverse Flux Permanent Magnet Disk Wind Power Generator with H-Shaped Stator Cores

This paper presents a novel transverse flux permanent magnet disk generator (TFPMDG) for wind power generation. The main features of its structure are the modular H-shaped stator cores and two simple rotor disks. What is different from the structures introduced in the references is that each H-shaped stator core is formed by two T-shaped iron cores and a permanent magnet (PM) rather than a complete H-shaped core, which makes the manufacturing simpler and easier. Each rotor disk consists of a rotor holder and several rotor bars, resulting in high robustness and reliability. Moreover, two circular coils in the H-shaped stator cores together with the stator disk are sandwiched by the two rotor disks, which improves the utilization of PMs. In this paper, the proposed TFPMDG is investigated in detail. Firstly, the structure and operating principle are introduced. Then, the magnetic circuit method is used to analyze the TFPMDG. Next, the three-dimensional (3D) finite element method (FEM) is employed to compute the magnetic field distribution and EMF at no load. According to the calculation result, the other three TFPMDGs with different shapes of rotor cores are proposed and analyzed for better back EMF, and then a generator with good performance is selected for load analysis. Finally, a prototype is fabricated and tested, and the simulated results are compared with the measured ones, which proves the rationality of the simulated results.

Presentation of a Novel Transverse-Flux Permanent Magnet Linear Motor and Its Magnetic Field Analysis Based on Schwarz–Christoffel Mapping Method

A novel transverse-flux permanent magnet linear motor (TFPMLM) named as double-sided double-excited one is proposed in this paper. First, the operational principle and structural advantages of the TFPMLM are presented. Then, the 3-D magnetic circuit structure of the TFPMLM is simplified equivalently into a 2-D one in order that Schwarz–Christoffel (SC) mapping method can be adopted to analyze the motor’s magnetic field and characteristics. Then, the air-gap flux density distribution, back voltage and force waveforms when at no-load and at load are calculated by the SC mapping method and 3-D finite-element method, respectively, for a prototype linear motor, The results from the two methods coincide much better with each other. At last, influences of magnet shape on the cogging force are studied by the SC method.

Application of Particle Swarm Optimization Combined With Response Surface Methodology to Transverse Flux Permanent Magnet Motor Optimization

As a result of the 3-D magnetic field and complex structure, existing motor design programs are not suitable for the transverse flux permanent magnet motor (TFPMM). Hence, a method combining particle swarm optimization (PSO) algorithm and response surface methodology (RSM) is proposed to optimize a TFPMM. The optimization aims to maximize the no-load electromotive force (EMF) to get higher torque density in the same volume of the motor. First, central composite design method is adopted for experiments on geometrical design variables. Next, the finite-element method is utilized for simulations to determine the coefficients of the second-order analytical model for the RSM. The optimal solution of the model is then obtained by MATLAB PSO toolbox. Finally, we compare the optimized model with a prototype owning the same volume. The results show that with optimization, the no-load back EMF is improved by 10%, so is the output torque, which illustrates the effectiveness of the optimization method.

Design of a Novel Consequent-Pole Transverse-Flux Machine With Improved Permanent Magnet Utilization

Severe leakage flux is a long-existed drawback in the transverse-flux permanent magnet machines (TFPMs), which results in a low permanent magnet (PM) utilization rate and prominent cogging torque in TFPMs. Aiming to solve this problem, this paper presents a novel consequent-pole transverse-flux machine (CP-TFM). The key is to artificially shift the upper and lower salient-pole rotors with a half-pole pitch and connect them with a ring-shaped core. Therefore, a complementary magnetic circuit is constructed to reduce the flux leakage between the adjacent poles as well as improve the PM utilization rate. To verify the feasibility of design, a 3-D finite-element model is established and its electromagnetic performance is evaluated. With the same peripheral dimension and copper loss, a quantitative comparison is carried out between the proposed CP-TFM and conventional TFPM. Finite-element simulation results reveal that compared to its contrast, the proposed solution can almost double the PM utilization ratio and effectively reduce the cogging torque.

Design, Analysis and Fabrication of a Novel Transverse Flux Permanent Magnet Machine with Disk Rotor

The purpose of this paper is to propose a novel design for the transverse flux permanent magnet (TFPM) disk-rotor generator with E and I-shaped cores (TFPMDEIG). Disk-shape structure increases the machine’s power factor, allows for high rotational speeds, decreases centrifugal force over permanent magnets, and is employed in wind turbines, due to its compact structures. As for other advantages for this structure, one can point to the fact that there are as many windings as machine’s pole pairs; these windings become parallel by observing the polarity. In other words, the total power of this machine is distributed between pole pairs, increasing the overall reliability of the machine. In this paper, first, the initial design algorithm and the basic formulas governing the behavior of the proposed structure using the equivalent magnetic circuit for each pole are provided, and the three-dimensional finite element method (3D-FEM) is used for verification of the algorithm. To validate the simulation results (3D-FEM), then, a prototype has been fabricated and experienced. The experimental results are in good agreement with simulation results.

Two-Dimensional and Three-Dimensional Core and Magnet Loss Modeling in a Radial Flux and a Transverse Flux PM Traction Motor

Analytical estimations and verified simulation models both in two dimension (2-D) and three dimension (3-D) are used to compare loss calculations of a radial flux machine (RFM) and a transverse flux machine (TFM) for a traction application. The analysis highlights the importance of a dense mesh and a high number of time steps when calculating core and magnet loss with an finite element method (FEM) program. It also shows the practical handling of loss modeling in 2-D and 3-D, including a stacking factor for the core lamination and magnet segmentation, and it is recommended that one is careful when comparing losses from 2-D and 3-D models. The TFM is shown to have much higher magnet loss compared with the RFM, although the TFM magnet design (with ring magnets) makes segmentation very effective.

Analysis on Axial End Flux Leakage and Resonance Characteristic of TFPM Linear Generator for Thermoacoustic Electric Generation System

According to 3-D magnetic circuit of the transverse flux permanent magnet linear generator (TFPMLG), the area of end flux leakage is divided into several zones, and the analytical expression of axial end flux leakage is derived through conformal transformation. The linear machine equivalent stiffness factor is derived through the calculation of detent force. Combining the linear machine with mechanical resonance property of thermoacoustic electric generation system, the computing method on resonance spring parameters of the system is provided. A 3-D finite-element model of TFPMLG is built to analyze the flux leakage distribution. The experimental results of the linear machine verified the validity of detent force and stiffness factor theoretical derivation; the research on axial end flux leakage and resonance spring parameters provides a valuable reference to other types of linear machines.

A Novel Transverse-Flux PM Linear Machine With Double Ω-Hoop Stator

A Novel Transverse-Flux PM Linear Machine With Double Ω-Hoop Stator

Design and optimization of a surface mounted transverse flux permanent magnet machine

Transverse flux permanent magnet machine (TFPM) is well known for its achievable high torque density and flexible topologies, which makes it especially suitable for wind power generation, electric vehicle and direct drive area. Existing TFPM topologies, however, are subject to high flux leakage and cogging torque. This paper deals with the design and optimization of a three phase surface mounted transverse flux permanent machine (SM-TFPM) to reduce flux leakage and cogging torque, the solutions of adjusting the interval between magnets and inserting auxiliary stator are suggested to realize the restriction of both flux leakage and cogging torque. The finite element analysis (FEA) results show the obvious effects, and the FEA design is validated via prototype experiment by using TMS320F28335 based controller and induction machine load. Based on the abovementioned researches, a further multi-objective optimization is applied by using differential evolution (DE) algorithm and the optimization results are compared with the previous design to demonstrate the improved performance

Performance Analysis and Modeling of a Tubular Staggered-Tooth Transverse-Flux PM Linear Machine

This paper investigates the performance analysis and mathematical modeling of a staggered-tooth transverse-flux permanent magnet linear synchronous machine (STTF-PMLSM), which is characterized by simple structure and low flux leakage. Firstly, the structure advantages and operation principle of the STTF-PMLSM are introduced, and a simplified one phase model is established to investigate the performance of the machine in order to save the computation time. Then, the electromagnetic characteristics, including no-load flux linkage, electromotive force (EMF), inductance, detent force and thrust force, are simulated and analyzed in detail. After that, the theoretical analysis of the detent force, thrust force, and power factor are carried out. And the theoretical analysis results are validated with 3-D finite-element method (FEM). Finally, an improved mathematical model of the machine based on d-q rotating coordinate system is proposed, in which inductance harmonics and coupling between d- and q-axis inductance is considered. The results from the proposed mathematical model are in accordance with the results from 3-D FEM, which proves the validity and effectiveness of the proposed mathematical model. This provides a powerful foundation for the control of the machine.

Performance Analysis of a Permanent Magnet Transverse Flux Generator With Double Coil

One of the disadvantages of permanent magnet (PM) transverse flux machines is high magnetic flux leakage in the stator and rotor cores. To improve the magnetic circuit of this class of machines, a generator with double coil was designed and built to research the problem. The machine topology is different from the topologies previously introduced in the literature. The main difference was in the stator and rotor configurations. The stator of the generator is divided by two parts: 1) outer and 2) inner. Two coils were placed in the inner and outer stators. The rotor with PMs was placed between the two stators. To diminish magnetic flux leakage in the stator and to decrease machine’s weight, magnetic poles were placed in aluminum housings. This resulted in high-density eddy currents induced in the housings, and a significant raise of the temperature. The housing of the machine was modified. The prototype test showed that the modified version of the stator contributed to a significant decrease in temperature. Electromechanical parameters and cogging torque of the proposed generator is also studied and presented in this paper.

A Novel Transverse Flux Permanent Magnet Generator With Double C-Hoop Stator and Flux-Concentrated Rotor

Transverse flux permanent magnet (TFPM) machine possesses the characteristic feature of decoupled electric load and magnetic load to obtain high power density. A novel TFPM generator (TFPMG) with double C-hoop stator and flux-concentrated rotor is proposed for low-speed applications, such as direct-drive power generation, which has larger torque capability and more poles than traditional double-side TFPMGs. The structure and operation principles of the generator are described in detail. The 3-D finite-element method (3-D FEM) is employed to compute the no-load magnetic field distributions. The analytical results, including flux density waveform, electromotive force (EMF) waveform, and inductance waveform of the armature winding, are obtained to verify the principle and feasibility of the proposed generator. The cogging torque is also analyzed and optimized by the 3-D FEM. A prototype is fabricated, and some experiments are conducted. The experimental results of back EMF and waveforms of current and voltage with different loads verify the FEM analysis previews well.

Analysis and Optimization of a Novel Tubular Staggered-Tooth Transverse-Flux PM Linear Machine

A novel tubular staggered-tooth transverse-flux permanent magnet linear synchronous machine is proposed. The machine is characterized by simple structure and low flux leakage. First, the structure and the operational principle are introduced. Second, the 3-D equivalent magnetic circuit model of the machine is built, and the analytical expression of the electromagnetic force is derived. Last, the force density and the force ripple are optimized with respect to three key dimensional ratios by the 3-D finite-element method. An optimized scheme with the high force density of $2.697 \times 10^{5}$ N/ $\text{m}^{3}$ and the low force ripple of 2.78% is achieved. In addition, the characteristics of the proposed machine are compared with other topologies of linear machines.

Multidisciplinary Design Analysis and Optimization of a PM Transverse Flux Machine With Soft Magnetic Composite Core

This paper presents a multidisciplinary analysis and a design optimization approach for a permanent magnet (PM) transverse flux machine (TFM) with a soft magnetic composite (SMC) core. First of all, electromagnetic, thermal, and modal analyses, and the manufacturing method of the SMC cores, are investigated for this machine. Meanwhile, a lumped 3-D thermal network model is developed for the thermal analysis. Then, a multidisciplinary optimization design model is proposed to minimize the material cost and to maximize the output power based on the proposed multidisciplinary analysis models. The numerical solutions obtained from electromagnetic and thermal analyses are validated by comparing them with the previous experimental results. As shown, the performance of this PM-SMC TFM can be improved greatly using the proposed approach. Finally, a finite-element model is employed to verify the performances obtained from optimal results in terms of thermal and modal analyses.