Transverse Flux Permanent Magnet Generator Research Articles

Analytical Performance Estimation of a Fall-Back Inner-Rotor Transverse-Flux Permanent Magnet Generator using Magnetic Equivalent Reluctance Circuit

The potential of wind energy resources is propelled fast and power extraction is increasing considerably due to the development of reliable and cost-effective wind turbine generators. Various permanent magnet (PM) wind generators have been implemented for wind power generation, among which, the conventional transverse-flux permanent magnet generator (TFPMG) is popular due to their higher torque density and simple coil design, but it has some disadvantages in comparison with radial flux PM generator, i.e., higher flux leakages and complex 3D flux pattern. In this article, a fall-back inner rotor transverse-flux PM wind generator FB-TFPMG has been investigated to override the disadvantages of conventional TFPMG. It employs half of the total PMs on the rotor and U-shaped stator cores. An analytical model of the proposed FB-TFPMG has derived using magnetic equivalent reluctance circuit (MERC) to predict the performance of the generator, i.e., flux densities in the air-gap, under aligned and unaligned conditions of rotor PMs with U-shaped stator cores. The results of the MERC model is verified with the results obtained through 3D finite element analysis.

Design and analysis of semi-closed stator core transverse flux permanent magnet generator

Purpose The purpose of this paper is to modernize the generator system of wind turbine concept that not only improves the efficiency and power density but also reduces the system cost making design simpler and less expensive, especially in large-scale production. Design/methodology/approach This paper presents a new permanent magnet transverse flux generator (PMTFG) for wind energy production. The key feature of its composition is the double armature coil in a semi-closed stator core. The main structural difference of the presented design is the use of double coil in the same space of semi-closed stator core and reduced number of stator pole pairs and rotor magnets from 12/24 to 10/20. 3D simulations are performed using finite element analysis (FEA) to measure induced voltage and magnetic field distribution at no load. The FEA is performed to quantify the change in flux linkage, induced voltage and output power as a function of different speeds and load current. Findings Results show that PMTFG with double coil configuration has improved electromagnetic performance in terms of flux linkage, induced voltage, output power and efficiency. The power density of 10/20 PMTFG with the double coil is 0.0524 KW/Kg, about an 18% increase compared to the conventional design. Research limitations/implications The proposed PMTFG is highly recommended for direct drive applications such as wind power. Originality/value Four models are simulated by FEA with single and double coil configuration, and load analysis is performed on all simulated models. Finally, results are compared with conventional PMTFG.

Mitigation of cogging torque in transverse‐flux permanent‐magnet machines with flux concentrators by step skewing of stator pole

The objective of this article is to study how the stator step skewing method can lead to the reduction of the cogging torque of a transverse-flux permanent-magnet (TFPM) machine with flux concentrators. Three structures are analysed and compared in terms of their influence of the skewed displacement on the cogging torque using the three-dimensional finite element method (3D-FEM). Thereafter, to validate the FEM results, cogging torque is calculated by applying a Schwarz–Christoffel (SC) conformal mapping. To apply this transformation, the 3D TFPM generator structure with axially magnetised permanent magnets (PMs) is converted into a 2D structure with radially magnetised PMs and the cogging torque of the machine is predicted using both the analytical method and 3D-FEM. The accuracy of the approach is demonstrated by the adequate agreement between the results obtained through this SC mapping and those of the 3D-FEM. In addition, two 100 W prototyped TFPM machines are designed, simulated, manufactured and tested to validate the effects of the step-skewed stator yoke on the predicted cogging torque and back-EMF.

Thermal Modeling and Analysis of a Novel Transverse Flux HAPM Generator for Small-Scale Wind Turbine Application

This article focuses on a Transverse Flux Permanent Magnet generator which benefits from Halbach-array permanent magnets. In this topology, a sinusoidal air-gap flux is achieved and thus, lower THD content and cogging torque is resulted. The Transverse flux generators can be a proper choice for direct drive, low speed, and high torque density applications such as wind turbines. Regarding the available small scale turbines in the market, an operating point is chosen for the proposed machine. The problem of a high torque density generator is thermal stresses which should be taken into consideration in the design and modeling process. Precise thermal modeling at the design stage can take the risk of the increase in machine temperature. Using an active component meshed model by considering the localized losses along with a lumped parameter circuit for the unmeshed parts is proposed for the understudy machine. A 3 kW, 320 rpm generator is designed and analyzed by considering the electromagnetic and thermal properties. It is shown that the magnetic-thermal modeling of the proposed machine is highly consistent with the experimental results.

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.

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.

Analysis of a Fall-Back Transverse-Flux Permanent-Magnet Generator

The conventional transverse-flux permanent-magnet generator (TFPMG), preferred for wind power applications, has a few limitations, e.g., the flux distribution in a U-shaped stator core is uneven, and its inactive permanent magnet (PM) poles lead to high magnetic flux leakage. In this paper, a new fall-back transverse-flux permanent-magnet generator (FB-TFPMG), suitable for direct-drive applications, is proposed to reduce the magnetic flux leakage between the stator cores and the PMs. In the proposed configuration, half the number of PMs (i.e., only active PMs) are employed with the elliptical-shaped stator core and toroidal-shaped coil. This leads to immediate benefit of lower mass and better flux utilization. The performance of the new topology is analyzed, under no-load and loaded conditions, using a 3-D finite-element tool, and the results are presented in comparison with the conventional TFPMG. The results show improved outcome of the proposed topology in comparison to the conventional TFPMG.

Cogging Torque Optimization of Novel Transverse Flux Permanent Magnet Generator With Double C-Hoop Stator

This paper deals with a sizing optimization approach to reducing the cogging torque and maximizing the flux linkage of a transverse flux permanent magnet generator with double C-hoop stator and flux-concentrated rotor. The previous investigations demonstrated that the cogging torque is significantly influenced by $k_{s}$ and $k_{r}$ , which denote the ratios of circumferential widths of stator hoop and rotor core to pole pitch, respectively. The 3-D finite-element method (FEM) is employed to investigate the relationship between the abovementioned ratios and the cogging torques of both single-phase and three-phase prototypes. The optimal ratios of $k_{s}$ and $k_{r}$ , which comply with the equation, i.e., $(k_{{ r}} >1-k_{{ s}} )\cap (k_{{ r}} >1-0.788~*~k_{{ s}} )=k_{r} >1-0.788~*~ k_{{ s}} $ , are selected, and the procedures are described. The FEM results show that the amplitude of the cogging torque can be reduced significantly due to the reshaped rotor core. Besides, two additional zero-crossing points can be observed with the increase in $k_{r}$ and the decrease in $k_{s}$ . The cogging torque can be decreased by 20% with a skewed rotor core. A three-phase prototype is optimally designed and manufactured to verify the optimization approach.

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.

Structural analysis and optimisation of transverse flux permanent magnet machines for 5 and 10 MW direct drive wind turbines

ABSTRACTThe transverse flux permanent magnet generator offers high power density in terms of active mass. Two configurations of this machine topology (referred to as TFPM‐1 and TFPM‐2) are described, and optimised electromagnetic designs are presented. Direct drive generators require a significant support structure, which is designed to minimise the deflection into the air gap due to inherent electromagnetic attraction forces. The design of these structures is also dependant upon the generator topology. Structural design tools, which can be used in a design office environment, have been developed for the transverse flux machine and verified using commercial numerical modelling packages. Generic disc and arm structures are used. Only static analysis has been performed, but this does provide the designer with an estimate for more detailed design. A comparison of mass is made between the two transverse flux machines and a more conventional iron‐cored permanent magnet generator. The comparison shows that TFPM‐2 has the lowest total mass at 5 and 10 MW, but the conventional iron‐cored machine is lighter than TFPM‐1. Copyright © 2012 John Wiley & Sons, Ltd.

Dynamic modeling of transverse flux permanent magnet generator for wind turbines

The transverse flux permanent magnet machines have become an interesting possibility for offshore wind turbines. These machines have the highest relation between electrical torque and weight of active materials. The pole pair modular construction could eliminate or lower the gear ratio used in conventional wind turbines. This paper presents a dynamic model of a wind turbine equipped with a transverse flux permanent magnet generator connected to a direct-current power system using a combination of 3D finite element generator model and an aerodynamic model. The results indicate that the model can give accurate response for steady-state operation and for wind speed variations.

Accurate Modeling of a Transverse Flux Permanent Magnet Generator Using 3D Finite Element Analysis

This paper presents an accurate modeling method that is applied to a single-sided outer-rotor transverse flux permanent magnet generator. The inductances and the induced electromotive ...

Conventional and TFPM Linear Generators for Direct-Drive Wave Energy Conversion

The archimedes wave swing (AWS) is a system that converts ocean wave energy into electric energy. The goal of the research described in this paper is to identify the most suitable generator type for this application. Of the conventional generator types, the three-phase permanent-magnet synchronous generator with iron in both stator and translator is most suitable, because it is cheaper and more efficient than the induction generator, the switched reluctance generator, and the permanent-magnet (PM) generator with an air-gap winding. The paper also proposes a new transverse-flux PM (TFPM) generator topology that could be suitable for this application. This new double-sided moving-iron TFPM generator has flux concentrators, magnets, and conductors on the stator, while the translator only consists of iron.