High Energy Rare Earth Magnets Research Articles

Toward Less Rare-Earth Permanent Magnet in Electric Machines: A Review

Many electric traction drive systems (ETDSs) are driven by electric motors primarily composed of high-energy rare-earth (RE) permanent magnets (PMs), such as neodymium-iron-boron (NdFeB) and samarium-cobalt (SmCo). Given the high cost of RE materials, there is a great interest among various industry sectors in searching for breakthrough technologies that reduce the consumption of high-energy RE magnets in their electromechanical energy conversion systems. The reduction of the magnetic volume is typically realized either by replacing a portion of the high-energy RE magnet with the low-energy ferrite magnet (knows as hybrid structure) or by modifying the magnetic arrangement of the machine itself, where a portion of the physical RE magnets is removed and replaced by induced magnets (known as consequent-magnetic pole structure). For this purpose, this article presents a review of the current state-of-the-art motor typologies with less-RE PMs and their key design challenges, followed up by a series of recommended guidelines to overcome related design challenges.

Efficient near Net-Shape Production of High Energy Rare Earth Magnets by Laser Beam Melting

In this publication we report on our progress in investigating the energy efficient production of rare earth permanent magnets by Laser Beam Melting in the powder bed (LBM). This innovative additive manufacturing process offers the potential to produce magnets of complex geometries without an energy intensive oven sintering step. Another advantage that increases the efficiency of this possible new process route is the high degree of material utilization due to a near net shape production of the magnets. Hence only little material is wasted during a post processing machining step. The main challenge in processing rare earth magnet alloys by means of LBM is the brittle mechanical behavior of the material and the change in microstructure due to the complete remelting of the magnet powder. We therefor expanded the parameter study presented in previous work in order to further increase relative density and magnetic properties of the specimens. In this context process stability and reproducibility could also be increased. This was achieved by investigating the impact of different exposure patterns and varying laser spot sizes. Simultaneously to the experiments the energy consumption of the LBM process was measured and compared with conventional rare earth magnet production routes.

Hybrid electromagnetic shock absorber for energy harvesting in a vehicle suspension

Electromagnetic harvesters need to be designed with a mechanism to amplify the coil relative velocity to ensure compact size and lower weight. This paper discusses a novel technique to use fluid link for velocity amplification in an electromagnetic shock absorber. Incorporation of the fluid amplification significantly improves harvested power, without affecting the system dynamics. Numerical modelling and experimentation of a prototype shock absorber comprising of high energy rare earth magnets have been presented. Peak coil voltage of 0.60–24.2 V was recorded during experimentation on the prototype. Experimental and simulation results validate that incorporation of the fluid amplification link improves the harvested electric power by 9702%. Comprehensive design procedure for better harvesting efficiency and vibration isolation has been discussed. Lastly incorporation of the shock absorber in McPherson strut suspension is illustrated. The real size version will be able to harvest peak power of 18–227 W for the suspension velocities of 0.15–0.4 m/s.

Stand-Alone Pico-Hydro Generation System using a High-Efficiency IPM Synchronous Generator

Abstract – This paper presents a successful stand-alone pico-hydro generation system using a high-efficiency interior permanent-magnet (IPM) synchronous generator. A 1-kW 4-pole V-type IPM generator with low voltage regulation is used for laboratory test in stand-alone hydro energy conversion system. It has been found from experimental results that the constant output voltage is supplied stably by the proposed system under wide speed range. Keywords : Hydro g eneration system, IPM generator, Automatic voltage regulation 1. Introduction Recently, global warming has become an important problem. In Japan, there has been a power-shortage problem because of the shutdown of the nuclear power reaction by the Great East Japan Earthquake on March 11, 2011. In such situation, the territorially distributed energy generation using wind or water power attracts attention. The development of permanent-magnet (PM) synchronous generators has progressed rapidly due in part to emergence of the high energy rare-earth magnets like neodymium-iron-boron (Nd-Fe-B) and many designs of PM rotors have been presented in recent years [1]-[6]. However, rare-earth materials such as neodymium and dysprosium are expensive and depend on China for 90% or more of the world share [7]. Therefore, the research for the substitution of Nd-Fe-B to Ferrite magnets has been reported [8]. However, it is considered that the downsizing of the generator needs the high energy rare-earth magnets in stand-alone small power generation system still now. Small wind or water power generation systems have been presented in recent years, for example, [9]-[12]. This paper presents a successful automatic voltage regulation of high-efficiency IPM synchronous generators for stand-alone pico-hydro power generation system. A 1-kW 4-pole V-type IPM generator with low voltage regulation [13] is used for laboratory test in hydro energy conversion system.

Comparison of Different Motor Types for Electricvehicle Application

SummaryThe drive of an electrk Vehicle (Fig.I) requires a small volume, a high power to weight ratio, a high efficiency, a wide speed range. reliability and low costs in manufacturing and maintenance. In this article is presented the comparison of . induction motors (ASIWN). permanent magnet synchmous motors (PMSM’s) and a permanent magnet synchronous motor with auxiliary exciting windings (HYB).Because of absence of maintenance and its large robustness the squirrel-cage ASM is absolutely suitable to equip an electric vehicle. To reach a wide speed range (over 7000 rpm) and a high efficiency the motor must be designed with low stray reactance’s and coppercage rotor. This does not lead to a weight optimal solution.The PAISM with high energy rare earth magnets has a higher efficiency than the ASM. because it does not need a magnetizing current. which produces additional losses. it can also reach speeds as high as the ASM, by feeding the stator windings with an additional negative direct current. But such properties are only possible with a small number of pole pairs.The HYB has a high number of pole pairs, that is more interesting from the weight point of view. but it needs auxiliary exciting windings. By field-strengthening at low speed the motor can deliver a high torque if necessary. By field-weak-ening in the rotor and feeding the suitor with a negative direct current the motor can also reach the maximal speed. Prototypes of each synchronous machine have been designed by FEM-analysis, built and measured on a test bench in the institute.

An improved design procedure for hybrid stepper motors

A design methodology for hybrid stepper motors is presented. It takes into account the saturation throughout the motor, allows for variations in magnet working point, and enables the designer to optimize the balance of coil and magnet MMFS (magnetomotive forces) to achieve a specified holding torque. The procedure is based on the use of the finite-element technique to generate permeance curves for the complex tooth/airgap region of the motor, accounting for localized saturation effects in the teeth. The curves are then used in a nonlinear lumped parameter network of the entire motor. The network models the motor's 3-D nature and may include other saturating elements as well as leakage permeances. By applying the virtual-work technique, the lumped parameter network is used to calculate torque/displacement characteristics as well as the winding inductance and back-EMF (electromotive force) constants. The technique has been used in the design and analysis of several industrial stepper motors utilizing high-energy rare-earth magnets. >