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Electric Machines
Published in Patrick Hossay, Automotive Innovation, 2019
The resulting rare earth magnetic alloys are nothing short of remarkable. Previously, magnets were made either of a ceramic compound of iron oxide and other metals, called ferrite, or an alloy of aluminum, nickel, and cobalt that produced a much stronger magnet called Alnico. Yet compared to current rare earth options, both of these have a very poor specific power, and would need to be many times larger to offer the same performance. In fact, the samarium–cobalt alloy (SmCo) that defined the first family of rare earth magnets proved more than twice as powerful as Alnico magnets and many times more powerful than ferrite magnets. An important point of comparison is the magnetism remaining after the external magnetic field that magnetized a material is removed, called remanence flux density. Also important is a magnet’s resistance to demagnetization, called coercivity. As the table below indicates, these factors, and the magnetic energy of the material, are remarkably greater in rare earth magnets. However, the very high cost of these magnets limits their use. An even more impressive and feasible option was defined with the next generate of rare earth magnets, neodymium–iron–boron (Nd2Fe14B or NIB). With just about twice the power of SmCo magnets, they are also lower cost. With the price of NIB magnets having dropped significantly over the past two decades, they are now the go-to choice for PM machines for everything from cordless tools to automobiles.
Mechanics and Electromagnetics
Published in Sergey Edward Lyshevski, Mechatronics and Control of Electromechanical Systems, 2017
The soft and hard ferromagnetic materials are characterized by the B–H curves, maximum energy product (BH)max [kJ/m3], Curi temperature, and mechanical properties. The term soft implies high saturation magnetization, low coercivity (narrow B–H curve), and low magnetostriction. The soft materials are used in magnetic recording heads. The hard magnets have wide B–H curves (high coercivity) ensuring high-energy storage capacity. These magnets (ceramic ferrite, neodymium iron boron NdFeB, samarium cobalt SmCo, Alnico, and others) are widely used in electric machines and electromagnetic actuators to attain high force, torque, and power densities. The energy density is given as the area enclosed by the B–H curve. The magnetic volume energy density is wm = ½B · H [J/m3]. Most hard magnets are fabricated using the metallurgical processes, e.g., sintering (creating a solid but porous material from a powder), pressure bonding, injection molding, casting, and extruding.
Direct Current Power Systems
Published in Stephen W. Fardo, Dale R. Patrick, Electrical Power Systems Technology, 2020
Stephen W. Fardo, Dale R. Patrick
Permanent-magnet DC Generator—A simplified diagram of a permanent-magnet DC generator is shown in Figure 7-11. The conductors shown in this diagram are connected to the split-ring commutator and brush assembly of the machine. The magnetic field is established by using permanent magnets made of Alnico (an alloy of aluminum, nickel, cobalt, and iron), or some other naturally magnetic material. It is possible to group several permanent magnets together to create a stronger magnetic field.
Study of a Spoke-Type Ferrite Structure as an Alternative to Surface-Mounted NdFeB PMSGs: A Performance Comparison Based on Getting the Same Efficiency
Published in Electric Power Components and Systems, 2023
Permanent magnets have the ability to deliver flux to the air gap of a magnetic circuit without a constant loss of energy. Many different types of permanent magnet materials are currently available in the industry. Iron, nickel, cobalt, alnico, ferrite, samarium–cobalt, and neodymium–iron–boron alloys are the types of permanent magnets currently used in the industry. Permanent magnets have magnetic flux density (B)-magnetic field intesity (H) B-H curves that represent large coercive force, high permanent magnetism, and high demagnetizing force. While NdFeB magnets have a very high BHmax value, AlNiCo magnets have high-temperature stability, and SmCo magnets can be used at high temperatures up to 300 °C. Ceramic magnets attract attention with their low cost. AlNiCo magnets can be easily demagnetized due to their low coercive forces and are very brittle. Ceramic magnets are also very hard and brittle, similar to AlNiCo magnets. The significant problems of rare earth resources such as limited supply and high cost emerge as the biggest disadvantages of NdFeB and SmCo magnets [3, 4]. Ferrite magnets offer easy production and more affordable price advantages. With these properties, they can be considered as an alternative to NdFeB magnets in case of proper design structure allows. Ferrites have a low residual flux density and a maximum operating temperature of approximately 350°, which results in a high volume and relatively high-weight machine [5].
Future of photovoltaic materials with emphasis on resource availability, economic geology, criticality, and market size/growth
Published in CIM Journal, 2023
G. J. Simandl, S. Paradis, L. Simandl
The term magnet materials, as used today in trade journals, designates primarily REEs and more specifically neodymium (Nd), praseodymium (Pr), samarium (Sm), dysprosium (Dy), and terbium (Tb) (Simandl et al., 2021). In some technical and industry documents, this term also includes Co. However, exploration and mining journals generally ignore materials used in older magnet technologies such as aluminum-nickel-cobalt (AlNiCo) and yttrium cobalt (YCo5) magnets. Most importantly, this term ignores materials used in affordable and relatively demagnetization-resistant ferrite or ceramic magnets (e.g., BaFe12O19 and SrFe12O19), which currently account for the bulk of global magnet production by weight. Modern neodymium–iron–boron (NdFeB) magnets, also referred to as REE magnets, contain approximately 30 wt.% REEs (mainly Nd and to a lesser extent Dy and lower concentrations of other REEs such as Pr and Tb).
Pumping Options for Versatile Test Reactor Molten Lead In-Pile Test Cartridge
Published in Nuclear Science and Engineering, 2023
Mohamed S. El-Genk, Timothy M. Schriener, Ragai Altamimi, Andrew Hahn
The ALNICO-5 and Hiperco-50 magnets have been considered in dc-EMP designs for circulating high-temperature alkali metals in terrestrial and space nuclear power applications. A submerged auxiliary pump with ALNICO-5 magnets, which have a curie point of ~ 800°C, had been used to circulate the liquid Na coolant in the Experimental Breeder Reactor-II27 (EBR-II). The ALNICO-5 generates a strong magnetic field for operation at temperatures up to 550°C (Refs. 28 to 30). At this temperature, the magnetic field is 93% of its saturation value at 20°C. Therefore, the ALNICO-5 magnets were used in the development of the present miniature, dual-stage dc-EMP for circulating molten lead at 500°C in the ELTA-CL options with raiser tube inner diameters of 57.0 and 68.8 mm (Fig. 4). The Hiperco-50 pole pieces at the ends of the ALNICO-5 permeant magnets (Fig. 4) improved the performance of the developed dc-EMP designs in this work by reducing the magnetic flux losses outside the active pumping regions. These pole pieces also helped generate uniform magnetic flux densities in the flow duct in the two pumping regions. The Hiperco-50 has one of the highest magnetic permeabilities of the commercially available soft magnets and a high curie point of ~940°C (Ref. 31).