PM Material Research Articles

Novel 6/7 Stator/Rotor Hybrid Excitation Doubly Salient Permanent Magnet Machine

One novel 6/7 stator/rotor hybrid excitation-biased flux permanent magnet machine (HE-BFPMM) is proposed in this paper. First, it discusses the new structure and operation principle in detail. Then, one improved design optimization technique is proposed to refine the HE-BFPMM based on a 2-D finite-element algorithm. Afterward, a comprehensive electromagnetic performance comparison between HE-BFPMM and original 6/7 stator/rotor BFPMM (ORI-BFPMM) has been made quantitatively by the premise of constant out radius and axial length. It indicates that, compared with ORI-BFPMM, the HE-BFPMM can demonstrate much higher no-load back electromotive force, lower torque ripple, higher PM material utilization ratio, and stronger flux-weakening capability.

Investigation of a Magnetic-Field Modulated Brushless Double-Rotor Machine With the Same Polarity of PM Rotor

Owing to getting rid of brushes and slip rings, the magnetic-field modulated brushless double-rotor machine (MFM-BDRM) can be a promising candidate for the electrical-continuously variable transmission (e-CVT) in hybrid electric vehicles (HEVs). However, since there are many magnetic-field harmonics with the high rotating speed in the air gap, the PM loss is a big problem in traditional MFM-BDRMs [1]. Therefore, a new MFM-BDRM with the same polarity of PM rotor is proposed, which has advantages of reducing PM loss, saving PM material and keeping good electromagnetic performance. The magnetic field distribution in the air gap, the back electromagnetic force (EMF) and torque performance of the proposed MFM-BDRM are investigated. To obtain the optimum design scheme, the influence of PM pole-arc coefficient on the torque performance is investigated. Then the torque performance is further optimized by the span ratio of magnetic blocks. To evaluate the overall performance of this new MFM-BDRM, a traditional MFM-BDRM with the same size is designed to compare their performances.

Automotive Electric Motors, Generators, and Actuator Drive Systems With Reduced or No Permanent Magnets and Innovative Design Concepts

Due to environmental and energy concerns, electric vehicles (EVs) and hybrid EVs (HEVs) are gaining increased attention. At the heart of the drive system of these vehicles is the electric machine and drive. For these applications, high power density, high torque density, wide speed range, and efficiency are of primary importance. To meet these demands, interior-permanent-magnet (IPM) machines have been widely used. However, IPM machines use rare-earth PMs (usually neodymium-iron-boron magnets) in their structure. The price of these types of rare-earth PMs has increased by orders of magnitude over several years. Due to the high cost and limited supply of this material, the use of IPM machines in HEV applications is now being challenged. In fact, many researchers are working on other machines that can compete with IPM machines in terms of size, efficiency, power, and torque density. With consideration of the above points, there is a timeliness to this important topic; thus, we are pleased to present this Special Section on Automotive Electric Motors, Generators, and Actuator Drive Systems With Reduced or No Permanent Magnets and Innovative Design Concepts of the IEEE Transactions on Industrial Electronics that consists of 12 papers reporting on the most recent research on automotive electric drive machines. Most of these papers focus on machines with less or no rare-earth PM material in their structure, although control is also important, and there are some papers related to this topic.

Investigation of the Rotor Demagnetization Characteristics of Interior PM Synchronous Machines During Fault Conditions

This paper investigates the transient magnetic behavior of an interior permanent-magnet (IPM) synchronous machine following a large transient current caused by a fault condition. A combination of finite-element (FE) analysis and numerical integration of the machine equations is used to calculate the currents resulting from a symmetrical three-phase short-circuit fault at the machine terminals, including magnetic saturation effects. FE analysis is further used to simulate the magnetic behavior of the machine when subjected to the fault currents, with a particular focus on the propagation of the demagnetizing MMF throughout the conductive laminations as well as the conductive PM material. Eddy currents induced in the laminations and magnet material are shown to impede the progression of the demagnetizing MMF. However, the transient analysis illustrates the manner in which the fault currents ultimately trigger the onset of irreversible demagnetization of significant portions of the rotor magnets in the analyzed machine. The transient demagnetization analysis method is extended to investigate the influence of several key design variables, including machine operating temperature and segmentation of the rotor magnets.

Compact Undulator for Cornell High Energy Synchrotron Source

Motivated by the needs of Cornell High Energy Synchrotron Source (CHESS), we developed and are now constructing a novel type of planar undulator magnet called CHESS Compact Undulator. The device consists of two pure permanent magnet (PPM) arrays mounted inside of a rectangular box-like frame on linear bearings providing magnet array motion along the beam axis. The outside frame dimensions are 156 mm 148 mm. Undulator is 1 meter long. It has 5 mm constant gap. The magnetic field strength is controlled by the array longitudinal motion (adjustable phase scheme). Magnetic structure has 24.4 mm period and maximum peak field 1.1 Tesla. The PM material is Nd-Fe-B of 40UH grade. The undulator magnet will be enclosed in a 273 (10.75) mm diameter cylindrical vacuum vessel while the driver mechanism responsible for moving the magnet array will be placed outside. The following sections describe mechanical and magnetic design of undulator and present results of the magnetic field measurement and evaluation of vacuum properties.

Design and Strength Analysis of Ultra-High Speed Permanent Magnet DC Rotor

The sintered neodymium-iron-boron (Nd-Fe-B) material is used in most of PM machines. The kind of PM materials has small tensile strength and cannot withstand large centrifugal force due to high rotational velocity. A nonmagnetic steel enclosure is needed to cover the PM material. The tensile stress of the PM can reduced by pre-pressure applied to the outer surface of the PM through shrink-fitting into the enclosure. Based on the elasticity theory and the elastic-plastic contact theory, in soft ANSYS it is feasibility to establish a finite element mechanical model of interference fit between the enclosure and motor rotor PM at high rotating speed. This paper simulates the effects of the temperature and rotating speed (centrifugal force) on the displacement and the contact pressure on the interference-fitting surfaces .By finite element non-linear contact model analysis, if setting up right fit clearance, this paper could ensure the security of the PM rotor under rotational velocity up to 300,000 r/min high and temperature up to 150°C.

Static Eccentricity Fault Diagnosis in Permanent Magnet Synchronous Motor Using Time Stepping Finite Element Method

This paper introduces a new index for noninvasive diagnosis of static eccentricity in permanent magnet synchronous motors (PMSM). Use of this index makes it also possible to precisely determine the eccentricity degree. The index is the amplitude of the harmonic components with a particular frequency pattern. Occurrence and increase of the fault degree cause the rise of amplitude of the harmonic components which can be used to diagnose the fault and determine its degree. To evaluate the ability of the proposed index for static eccentricity detection and estimation of its severity, the correlation between index and eccentricity degree is calculated. Then a three-layer artificial neural network is employed to classify the current and torque profiles to one of the four possible classes of eccentricities. After all, a white Gaussian noise is added to the both measured current and torque and robustness of the proposed index is analyzed with respect to the noise variance. A PMSM under static eccentricity fault is modeled using time stepping finite element method. This modeling includes all geometrical and physical characteristics of the machine components, non-uniform permeance of the air gap and non-uniform characteristics of the PM material. Use of this precise modeling makes it possible to access the demanded signals for a very high precision processing.

Creep behavior of ingot and powder metallurgy 6061Al

The creep behavior of 6061Al alloy obtained by ingot metallurgy and powder metallurgy, IM and PM, respectively, has been investigated in the context of published studies on this alloy. The behavior of the IM alloy in a given range of temperatures where the β, Mg 2Si, precipitates are formed, is dominated by dislocation climb-controlled creep and aluminum self-diffusion as rate controlling process. A dependence of the β inter-particle distance, λ, with the applied stress, σ, of the form λ ≈ 1 / σ is found when the creep data are analyzed in the context of the sub-structure invariant model. The superior creep resistance of the PM material can be explained if a threshold stress, σ 0, is brought into the creep equation. This term is the difference between the applied stresses needed to reach a given strain rate in the PM and the IM alloys, and correlates well with a particle–dislocation interaction mechanism according to the Artz–Wilkinson model.

The structure and properties of the PM material Vanadis 30 with surface treatment

The structure and properties of the PM material Vanadis 30 with surface treatment

Surface Modification of Powder Metallurgy Components With a Direct Diode Laser

A 1200 W diode laser was used to modify the surface properties of a fully-sintered ferrous PM material. Two modifications were investigated; transformation hardening of selected areas and sealing of surface porosity by re-melting. The diode laser was used because the beam footprint is large (5×0.5 mm) and the wavelength short (0.94 μm). Processed samples were examined using metallographic and hardness testing techniques. Results indicated that hardness comparable to induction hardening could be achieved and re-melting could be controlled to seal porosity. Further work now needs to be undertaken to convert this demonstrated potential into a commercial reality.

Evaluation of As-Hipped PM High Speed Steel for Production of Large-Diameter Cutting Tools

Powder Metallurgy has been presented as an important process for producing metallic materials. Specially for high speed steels, it presents many advantages, as finer microstructures and alloy compositions that could not be feasible thought other processes. For large diameter bars, powder metallurgy is important because it produces more isotropic materials, with better carbide distribution, increasing the mechanical properties and notably the toughness. The present work aimed to characterize M3:2 high speed steel produced by powder metallurgy and compare its properties with conventional M2, in bar diameters between 76 and 91 mm. The steels were hardened using austenitizing temperatures varying between 1080 and 1200 °C; tempering was performed at 560 °C. For all austenitizing temperatures, bend toughness and microstructure were analysed and isotropy was evaluated comparing toughness values in transverse and longitudinal directions. The results show that, in the same hardness levels, PM M3:2 high speed steel is tougher than conventional M2. Besides, toughness in PM material is completely isotropic while M2 present differences in relation to the sample direction. Toughness results are closely related to the microstructure of materials, as PM material has a more homogeneous and finer distribution of primary carbides. Thus, the as-HIPed powder metallurgy high speed steel is shown as an important option to improve mechanical properties with maximum isotropy.

Chromium Steel Powders for Components

Chromium as an alloying element is of great interest due to its low cost, high hardenability and possibility to recycle. Use of pre-alloyed chromium powders has increased recently due to its accessibility at low cost. Low total cost is and has been the driving force to convert parts made from conventional steel to PM material. By use of pre-alloyed chromium material, the PM industry can further increase its market share, compared to conventional steel. Two pre-alloyed iron powders, one for high strength applications containing 3 % Cr and 0,5 % Mo and one for medium strength applications containing 1,5% Cr and 0,2% Mo are considered in this paper. The mechanical properties for mentioned materials in the carbon range from 0,2 to 0,8% are described.

Quantitative analysis of fatigue properties of PM material

Quantitative analysis of fatigue properties of PM material

Design and development of a permanent magnet torquer for a gyroscope

In this paper, the computer aided design and development of an efficient PM torquer used in a Gyroscope is presented. The initial design using the conventional method has been analyzed and tuned using the 2-D and 3-D finite element (FE) models of the torquer. The radial magnet configuration, with two working airgaps and also with PM rings on both sides of the airgap, is found to be the optimum, owing to maximum coil utilization, increased flux density, minimum leakage flux and low coil-inductance. Samarium cobalt is used as the PM material as it makes the torquer very compact even with larger airgaps. Test results of the developed PM torquer having a scale-factor of 173.3/spl deg//hour/mA, match fairly with the computed values.

The effect of processing on the mechanical properties and interfacial strength of aluminium/TiC MMCs

The microstructure and mechanical properties of aluminium/TiC MMCs made by powder processing (PM), by a flux-casting process, and by melting PM material, have been compared. Particle clustering is more prevalent in cast than in PM composites, but the grain-refining nature of TiC particles significantly reduces the degree of clustering commonly observed in cast MMCs. Melting PM material enables oxide films to ‘trawl' the particles into large clusters. The stiffness and ductility are similar for cast and the PM composites but melting the PM material results in significant reductions in strength and ductility. In all cases, composite ductility is enhanced by extrusion through the removal of porosity and the break-up of particle clusters. Modulus measurements as a function of plastic strain indicate that rates of damage accumulation are lowest, and hence interfacial bonding is strongest, in cast composites as a result of the attainment of intimate contact and strong chemical bonding between the two phases.

Powder production by recycling waste products: A.R.Ness et al. (Bradley University, USA.)

Automotive steering columns use a variety of levers to lock the tilt mechanism in position. A PM material has been developed to withstand the impact and hardness performance requirements of this application. The part only requires honing of the pivot hole to meet the specified tolerance. Long term plans are to achieve the performance requirements using a modified version of the material. This has a higher graphite addition and can be used after tempering the ‘as-sintered’ product, say Brian James and Thomas Murphy of Hoeganaes Corp Riverton, Riverton, New Jersey, USA, and Vernon Potter of Presmet Corp, Worcester, Massachusetts, USA.

Effects of time and temperature of nitrocarburization on corrosion resistance of steel: A.L.Klein et al. (Federal University of St. Caterina, Brazil.)

Automotive steering columns use a variety of levers to lock the tilt mechanism in position. A PM material has been developed to withstand the impact and hardness performance requirements of this application. The part only requires honing of the pivot hole to meet the specified tolerance. Long term plans are to achieve the performance requirements using a modified version of the material. This has a higher graphite addition and can be used after tempering the ‘as-sintered’ product, say Brian James and Thomas Murphy of Hoeganaes Corp Riverton, Riverton, New Jersey, USA, and Vernon Potter of Presmet Corp, Worcester, Massachusetts, USA.

Characteristics of reactor for deposition of thick diamond films : B.Lux et al. (University of Technology, Vienna, Austria.)

Automotive steering columns use a variety of levers to lock the tilt mechanism in position. A PM material has been developed to withstand the impact and hardness performance requirements of this application. The part only requires honing of the pivot hole to meet the specified tolerance. Long term plans are to achieve the performance requirements using a modified version of the material. This has a higher graphite addition and can be used after tempering the ‘as-sintered’ product, say Brian James and Thomas Murphy of Hoeganaes Corp Riverton, Riverton, New Jersey, USA, and Vernon Potter of Presmet Corp, Worcester, Massachusetts, USA.

Advances in PM structural and material process technology : R.Link. (Mannesmann Demag AG, Germany.)

Advances in PM structural and material process technology : R.Link. (Mannesmann Demag AG, Germany.)

自動車焼結部品の高付価値化 材料からみた自動車焼結部品の技術展望

There are two major trends of PM material development. The first is PM products application to the structural parts of automobiles which were originally made of conventional cast iron, carbon steel or alloyed steel.The PM materials were improved based on the alloyed material design, optimum manufacturing process and conditions to obtain comparable mechanical properties with them. The second is unique PM materials having heat and wear resistant properties utilizing PM advantage of flexibility in alloy elements and microstructures. It is understood that there is getting no economical advantage of the PM materials for the former application unless any further new development concept implemented.In this paper, existing concerns for PM materials to be more widely applied to the automobiles and future trend of their development are mentioned focusing on iron base materials.