quasi-Halbach Array Research Articles

Analysis of an Axial-Flux Slotted Limited-Angle Torque Motor with Quasi-Halbach Array for Torque Performance Improvement

Better torque performance and higher reliability have long been the focus of research for slotted limited-angle torque motors (LATMs), which are primarily used to position first-stage valves in electrohydraulic servosystems. This paper presents a high reliability axial-flux slotted LATM with quasi-Halbach array for torque performance improvement including constant torque range (CTR) and output torque. Firstly, the structure with two sets of windings and the operation principle of the proposed slotted LATM is analyzed. Secondly, a brief design procedure is presented, the structure selections of open slot and double-stator single-rotor (DSSR) interior rotor with surface mounted quasi-Halbach permanent magnet (PM) array are illustrated, and the geometric parameters are optimized to obtain the optimal design of the proposed slotted LATM. Then, 3-D finite-element method (FEM) is employed to compare the proposed slotted LATM with the conventional surface mounted PM slotted LATM in terms of cogging torque, no-load back EMF, and output torque, and the results show that the proposed LATM with quasi-Halbach array has a 10% improvement in output torque and a 25% improvement in CTR. Meanwhile, the flux linkages and torque performance of the two sets of windings under various conditions verify good magnetic isolation. Finally, prototypes of two different rotor types are manufactured and a series of experiments are performed to validate the analysis.

A Study on Linear Generator Characteristics in Free Piston Engine

The linear generator (LG) is integrated into a system that called the free piston linear generator (FPLG). In recent year, free piston engine that is studied by many researchers, has some advantages. Therefore, the application of the line generator in free piston for converting the chemical energy to electrical energy that can be used for plug-in hybrids to extend the range of operations as an alternative energy converter. Therefore, the optimizing of linear generator performance be able to significantly reduce the vehicle's fuel consumption. The parameters in permanent magnet linear electric machine (PMLEM) are designed by Maxwell software and the optimal parameters is carried out via the flux density. To achieve this goal, a linear generator in free piston engine with a flat structure and quasi-Halbach array flux structure was proposed. The simulation of linear generator is performed based on the speed ranges in the New European Driving Cycle (NEDC) for a mid-size car. In the study, a linear electrical machine (LEM) is designed by Maxwell software with translator that has various diameters. The results show that the suitable parameters for stator and rotor about 7.7 mm and 14 mm, respectively. Because the flux density for this design’s stator and rotor yoke avoids saturation state and generates the highest electrical output compared to the other states. Besides, the paper also examined the power output at different frequencies from 15 Hz to 50 Hz, corresponds to a velocity amplitude of 3.6 m/s to 12 m/s. The simulation result shows that the frequencies from 15Hz to 30 Hz with 4.8 m/s to 7.2 m/s (1200 rpm to 2100 rpm), respectively meets engine speed operation ranges in hybrid vehicle and these frequencies produce the power output that increases considerably about 7.5 kW at 30 Hz.

Magnetic Design Aspects of the Trans-Rotary Magnetic Gear Using Quasi-Halbach Arrays

This article investigates magnetic design aspects of the trans-rotary magnetic gear (TROMAG) that using a quasi-Halbach array. TROMAG is a magnetic gear that converts high-force, low-speed linear motion to low-torque, high-speed rotational motion and vice versa. It is shown that quasi-Halbach magnetization significantly improves the force capability of the device compared to that of radial magnetization. Finite element analysis is used to study several design aspects of the quasi-Halbach TROMAG, including optimization of magnet dimensions and core thickness, effect of air gap length, effect of magnet remanent flux density, and distribution of flux density in the air gap. Moreover, the possibility of demagnetization is studied, and it is shown that if the quasi-Halbach TROMAG becomes overloaded repeatedly, demagnetization of magnets can degrade its force performance down to that of a similar TROMAG with radial magnetization. A quasi-Halbach TROMAG is prototyped, and static force and flux measurements verify the theoretical results.

Design and Characteristics Analysis of Coaxial Magnetic Gear for Contra-Rotating Propeller in Yacht

In this article, the design and characteristic research of the coaxial magnetic gear for the contra-rotating propeller in the premium yacht are presented. The scale-down model of 1/25 is reviewed as the research of the applicability of the coaxial magnetic gear. The space harmonic characteristics of the magnetic field in the coaxial magnetic gear with the low gear ratio from 1 to 2 are investigated, and the optimized models with the surface-mounted permanent magnet and quasi-Halbach array are obtained using the response surface method. In the several operating points of the diesel engine, the magnetic loss and the resultant thermal characteristics are analyzed and compared in each model. Finally, the desired coaxial magnetic for the contra-rotating propeller in the premium yacht is achieved.

Analysis of a Flux Reversal Machine With Quasi-Halbach Magnets in Stator Slot Opening

Flux reversal permanent magnet (FRPM) machine, with magnets mounted on or inserted into the stator, is favorable for the direct drive applications. In this paper, an FRPM machine with Quasi-Halbach array magnets in stator slot opening is introduced. The operation principle of the proposed machine is presented, and the combination of stator and rotor slot number is given. Several key parameters, that are split ratio, stator and rotor slot opening ratio, magnet ratio, and magnet thickness are carefully investigated, while four proposed FRPM machines with 12 stator slots and 10, 11, 13, 14 rotor slots are optimized for better performance. Moreover, the proposed FRPM machine is compared with a conventional FRPM machine, the analysis results indicate that the torque density of proposed machine is 2.2 times that of the conventional FRPM machine under the same copper loss with almost the same magnet usage. Finally, a 12 stator slot/10 rotor slot FRPM prototype is built to verify the theoretical analysis.

Dual Quasi-Halbach Linear Tubular Actuator With Coreless Moving-Coil for Semiactive and Active Suspension

This paper proposes the application of a specific topology of coreless linear tubular actuator for semiactive and active suspension systems. The actuator consists of two quasi-Halbach arrays of permanent magnets, inner and outer, and a moving-coil armature. Some of the advantages of this actuator for the proposed applications include low moving mass, low ripple of force, reduced magnetic losses, and high force density. The paper also introduces a new method for determining actuator requirements to operate with an active and/or semiactive suspension system and presents the application of the proposed approach to a harmonically base excited single degree-of-freedom suspension system. Additionally, the electromagnetic model for magnetic field distribution, open-circuit induced voltage, and axial force and force ripple was developed and validated by means of finite-element analysis and with experimental results obtained from a prototype.

Analytical predictions and analysis of electromagnetic field and torque for eddy-current couplers with Quasi-Halbach magnet array

Analytical predictions and analysis of electromagnetic field and torque for eddy-current couplers with Quasi-Halbach magnet array

Research on the Field-Modulated Tubular Linear Generator With Quasi-Halbach Magnetization for Ocean Wave Energy Conversion

A field-modulated tubular linear generator (FMTLG) with quasi-Halbach magnetization is proposed for ocean wave energy conversion. The FMTLG, which is equipped with field-modulated technology and quasi-Halbach arrays, can overcome the disadvantages of heavy weight and inefficiency caused by low-speed ocean waves to some extent. To design and optimize the FMTLG in a short time, the open-circuit magnetic field distribution is established with an analytical method. Results of a finite-element method show that the back EMF of the FMTLG is 43% higher than that of a tubular linear permanent magnet generator (TLPMG) with quasi-Halbach magnetization. A novel assistant tooth of the FMTLG makes the cogging force eight times smaller than that generated by the TLPMG. Finally, a prototype is manufactured to verify the simulation results by experiments.

Permanent Magnet Tubular Generator with Quasi-Halbach Array for Free-Piston Generator System

In this paper, the performance of a free-piston generator system with tubular single-phase stator winding is investigated for three different configurations of permanent magnet arrays on the mover: radial, rectangular quasi-Halbach and trapezoidal quasi-Halbach arrays. The optimal shape of the rectangular quasi-Halbach magnetization is obtained by employing an optimization technique called Imperialist Competitive Algorithm (ICA), and the results are compared with the previously developed permanent magnet linear generator (PMLG) with magnets of radial magnetization. Then, the resultant design of rectangular quasi-Halbach array, is changed to trapezoidal quasi-Halbach array and its performance is compared with other types of magnet arrays. The employed ICA is based on the analytical model of the magnetic flux distribution in air-gap, and is further verified by a nonlinear transient finite element (FE) model. The FE model has been developed to study the performance of the reciprocating PMLG. The accuracy of the proposed FE model is exemplified by comparing the calculated results with the experimental ones regarding the PMLG with radial magnetization.

Design of a Tubular Permanent Magnet Actuator for Active Lateral Secondary Suspension of a Railway Vehicle

This paper describes the finite element (FE)-based design of a slotted tubular permanent magnet actuator (TPMA) used in railway vehicle active lateral secondary suspension that improves the actuator’s thrust and lowers its cogging force under thermal and geometric constraints. To consider the electromagnetic and thermal fields and the complex interactions among the design variables, design was carried out in an electromagnet and thermal field environment using accurate and time-effective FE analysis. A six-slot prototype model was fabricated to estimate critical thermal parameters, which are difficult to compute without experiments. Three-dimensional FE analysis using the determined thermal parameters was adopted to calculate the precise thermal distribution of the TPMA and verify the forced air-cooling effect. A prototype TPMA with a quasi-Halbach array of permanent magnets and a moving magnet was manufactured through the FE-based design process; the dynamic, electromagnetic, and thermal characteristics of the prototype TPMA were validated experimentally.

A Study of the Influence of Quasi-Halbach Arrays on a Torus Machine

This paper aims to analyze the influence of quasi-Halbach arrays on the performance of an axial-flux machine with slotless toroidal core (Torus machine). The analysis was performed using a 3-D finite-element simulation of two machines, with one machine equipped with a quasi-Halbach array and a second with a conventional design with axially magnetized permanent magnets. These simulations were carried out in order to compare their performance. It was observed that the employment of quasi-Halbach arrays increases the torque density and the effective no-load terminal voltage.

Analytical Prediction of Torque Characteristics of Eddy Current Couplings Having a Quasi-Halbach Magnet Structure

A generic analytical frame for evaluating the torque performance of eddy current coupling equipped with a quasi-Halbach permanent magnet (PM) array is given, where the motional eddy current problem is represented by a four-layer boundary value problem. The effective magnetic characteristics and the field equation associated with the quasi-Halbach array are described in detail. To effectively predict the actual electromagnetic force at any slip speed, the eddy current distributions in the low-speed and high-speed cases are, respectively, investigated, and a modified 3-D correction factor is subsequently developed. A verification process is implemented by a 3-D finite-element analysis using the fixed computational grid method. The effects of the thickness of PM back iron on the degree of saturation and then on the variation of torque are investigated, and the impact of the eddy currents induced in the conductor back iron on the overall torque in the whole slip-speed range is also assessed.

Design Methodology of a Dual-Halbach Array Linear Actuator with Thermal-Electromagnetic Coupling.

This paper proposes a design methodology for linear actuators, considering thermal and electromagnetic coupling with geometrical and temperature constraints, that maximizes force density and minimizes force ripple. The method allows defining an actuator for given specifications in a step-by-step way so that requirements are met and the temperature within the device is maintained under or equal to its maximum allowed for continuous operation. According to the proposed method, the electromagnetic and thermal models are built with quasi-static parametric finite element models. The methodology was successfully applied to the design of a linear cylindrical actuator with a dual quasi-Halbach array of permanent magnets and a moving-coil. The actuator can produce an axial force of 120 N and a stroke of 80 mm. The paper also presents a comparative analysis between results obtained considering only an electromagnetic model and the thermal-electromagnetic coupled model. This comparison shows that the final designs for both cases differ significantly, especially regarding its active volume and its electrical and magnetic loading. Although in this paper the methodology was employed to design a specific actuator, its structure can be used to design a wide range of linear devices if the parametric models are adjusted for each particular actuator.

Design and analysis of novel moving-coil linear compressor for air brake system in electric vehicles

This paper presents a novel direct-drive linear compressor for air brake system in electric vehicles. By integrating the free piston and mechanical springs into a moving-coil type electromagnetic linear oscillating actuator (EMLOA), the structure of the proposed linear compressor is increasing compact. Moreover, the novel features, such as high thrust force constant, better controllability, and high resonant frequency, enable the linear compressor to operate most efficiently at resonance. The thrust force constant is enhanced by employing quasi-Halbach array and is tested to be high (74 N/A) and unchanged over the whole stroke. Dynamic modeling and experiment validation are performed to analyze dynamic characteristics of the linear compressor. The experimental and simulated data agree well, by regulating the frequency and amplitude of the excitation current, the high efficiency of the EMLOA (91.7%) and the low energy volume ratio of the linear compressor (7.3 kW/(m 3 /min)) indicate that the proposed linear compressor is significant energy saving compared with conventional compressors.

Research on a permanent magnet tubular linear generator for direct drive wave energy conversion

An external tubular linear permanent magnet generator (ETLPMG) is proposed for direct drive wave energy conversion. ETLPMG with quasi-Halbach array is larger in the air gap magnetic flux density than the internal and radial magnetisation one. An assistant tooth and fractional slot are implemented to decrease the detent force. The power density of ETLPMG is about 7–8 times for that of the internal one and the efficiency reached 90.03% at 18 Ω condition. The characteristics of the ETLPMG are analysed with a finite element analysis. Finally, a prototype is manufactured to verify the simulation results by some experiment tests.

Three-Dimensional Magnetic Field Modeling of a Cylindrical Halbach Array

A semi-analytical description of the 3-D magnetic field distribution of a cylindrical quasi-Halbach permanent magnet array is derived. This model avoids the necessity of time-consuming finite element analyses and allows for fast parameterization to investigate the influence of the number of segments on the magnetic flux density distribution. The segmented magnet is used to approximate an ideal radial magnetized ring in a cylindrical quasi-Halbach array. The model is obtained by solving the Maxwell equations using the magnetic scalar potential and describes the magnetic fields by a Fourier series.