Nanostructured Magnets and High-Power-Density Synchronous Generators

S.E. Lyshevski
Rochester Institute of Technology,
United States

Keywords: nanostructured magnets, synchronous generators, power generation, energy harwesting

Summary:

This paper examines enabling nanotechnology solutions for power generation systems (GGS) to improve and empower clean and renewable energy systems [1, 2]. The goal is to design electric machines with nanostructured magnets. We design optimized high-energy density Alnico magnets which meet the specifications for synchronous generators. Generators should guarantee safety, affordability, optimal energy conversion, minimal losses, maximum power density, etc. The studied nanostructured magnets [3-5] and permanent-magnet generators [6-9] can be used and commercialized in light-, medium- and heavy-duty commercial and industrial PGS from 1 kW to 1,000 MW. The proposed solutions uniquely suit automotive, aerospace, naval and other systems. We focus on affordable technology for current and future energy and power industries. The studied synchronous generators are used in wind, hydro, nuclear and other PGS. High-energy, high-power and high-torque densities electric machines and transducers require application-specific permanent magnets with required characteristics and capabilities (BH curve, coercivity, magnetic flux, stability, losses, etc.). In high-performance actuators and generators, the rare-earth SmCo and NdFeBr magnets are commonly used due to high energy product (BH)max. However, these magnets may not ensure adequate thermal stability, must be coated to prevent corrosion, brittle, sensitive to mechanical impact, prone to chipping and cracking, etc. Moreover, rotors and stators are made from high-permeability laminated electrical steel. One increases the air gap with attempts to ensure near-sinusoidal and uniform magnetic coupling, as well as reduce varying reluctance, torque ripple, cogging and other undesirable phenomena. The enabled nanostructured AlNiCo alloys may meet the spectrum of imposed requirements and ensure performance compared with or surpassing rare-earth magnets. One may refine magnetic domains, magnetic anisotropy, crystallographic alignment, crystalline structure and microstructure (composition, size, texture, separation, etc.) in order to control and optimize magnet characteristics. The nanostructured Alnico magnets have sufficient energy product (BH)max, high remanent force (Br), superior corrosion resistance, high Curie and operating temperatures, etc. High (BH)max and coercive force Hc are achieved by decreasing particle size because the maximum values correspond to the single-domain size (acicular Co-Ni crystal diameter is ~30 to 50 nm with interparticle spacing ~50 nm). The micrometer size is achieved by using ball mill, while, nanoparticles are prepared by hydrogen plasma metal reaction (HMPR). Alnico 5Fe,8Al,14Ni,24Co,3Cu with the particle diameter from ~10 to 40 nm are examined. The nanoparticles have the same crystalline structure and lattice parameter as powdered metallurgical sintered (Hc and BHmax are ~50 kA/m and 34 kJ/m3) and cast (Hc and BHmax are ~55 kA/m and 50 kJ/m3) Alnico 5 alloys. The JH and BH curves are reported in Figure 1. Optimal structural and geometric design of Alnico magnets for synchronous machines is performed. The Alnico magnets images are illustrated in Figure 2. The proof-of-concept permanent-magnet synchronous generators, shown in Figure 3, are examined. Our findings promise one to ensure an affordable technology improvement to current and future energy and power systems. This paper focuses on innovative solutions, practical technologies and enabling design tools in designing energy-efficient high-efficiency generators.