Amount Of Permanent Magnet Material Research Articles

Analysis and Optimization Design of U-Shaped Ironless Permanent Magnet Linear Synchronous Motor

The working speed of the U-shaped ironless permanent magnet linear synchronous motor is determined by the frequency and pole pitch. When the motor’s working speed is required to be constant, different combinations of frequency and pole pitch can be chosen. This article mainly discusses the influence of the pole pitch on the motor performance when other parameters are kept constant. First, the magnetic field of the motor permanent magnet is analyzed using the equivalent magnetizing current method to discuss the relationship between the pole pitch and the motor air gap magnetic field. Then, the finite element method is used to analyze the influence of the pole pitch on the motor air gap magnetic field, transverse edge effect, and electromagnetic thrust considering the saturation effect of the magnetic yoke. The research shows that under the conditions of constant motor basic structural parameters and speed, and the same amount of permanent magnet material, both the air gap magnetic density and the motor thrust line density have maximum values as the pole pitch changes. The research results have certain guiding significance for the design of this type of motor.

Rotating magnetocaloric effect in polycrystals—harnessing the demagnetizing effect

Climate change and the increasing demand for energy globally have motivated the search for a more sustainable heat-pumping technology. Magnetic refrigeration stands as one of the most promising alternative technologies for clean and efficient heat pumps of the future. The rotating magnetocaloric effect (RMCE) has previously been studied in materials with magnetocrystalline anisotropy due to its potential to improve devices by requiring only a single magnetic field region, but these materials are fragile and costly to obtain, making them inviable for applications. It has been shown that by exploiting the demagnetizing effect, an RMCE is, in fact, attainable in any polycrystalline magnetocaloric sample with an asymmetric shape, without requiring magnetocrystalline anisotropy. Using gadolinium as a case study, we provide a theoretical framework for computing the demagnetizing field-based RMCE and present thorough experimental verification for different magnetic field intensities and a wide temperature range. Direct measurements of the RMCE in gadolinium reveal that a significant adiabatic temperature difference (1.2 K) and refrigerant capacity (7.44 J kg−1) can be attained within low magnetic field amplitudes (0.4 T). Utilizing lower magnetic field intensities in a magnetocaloric heat pump can significantly diminish the need for permanent magnet materials, thus reducing the overall device cost, size, and weight, ultimately enhancing the feasibility of mass-producing such devices.

Influence of the Amount of Permanent-Magnet Material in Fractional-Slot Permanent-Magnet Synchronous Machines

The efficiency of permanent-magnet (PM) synchronous machines with outer rotor and concentrated windings is investigated as a function of the mass of magnets used, keeping the power, volume, and mechanical air-gap thickness constant. In order to be useful for electric vehicle motors and wind turbine generators, the efficiency is computed in wide speed and torque ranges, including overload. For a given type and amount of magnets, the geometry of the machine and the efficiency map are computed by analytical models and finite-element models, taken into account the iron loss, copper loss, magnet loss, and pulsewidth-modulation loss. The models are validated by experiments. Furthermore, the demagnetization risk and torque ripple are studied as functions of the mass of magnets in the machine. The effect of the mass of magnets is investigated for several soft magnetic materials, for several combinations of number of poles and number of stator slots, and for both rare earth (NdFeB) magnets and ferrite magnets. It is observed that the amount of PM material can vary in a wide range with a minor influence on the efficiency, torque density, and torque ripple and with a limited demagnetization risk.

Iso-geometric shape optimization of magnetic density separators

Purpose – The waste recycling industry increasingly relies on magnetic density separators. These devices generate an upward magnetic force in ferro-fluids allowing to separate the immersed particles according to their mass density. Recently, a new separator design has been proposed that significantly reduces the required amount of permanent magnet material. The purpose of this paper is to alleviate the undesired end-effects in this design by altering the shape of the ferromagnetic covers of the individual poles. Design/methodology/approach – The paper represents the shape of the ferromagnetic pole covers with B-splines and defines a cost functional that measures the non-uniformity of the magnetic field in an area above the poles. The authors apply an iso-geometric shape optimization procedure, which allows us to accurately represent, analyze and optimize the geometry using only a few design variables. The design problem is regularized by imposing constraints that enforce the convexity of the pole cover shapes and is solved by a non-linear optimization procedure. The paper validates the implementation of the algorithm using a simplified variant of the design problem with a known analytical solution. The algorithm is subsequently applied to the problem posed. Findings – The shape optimization attains its target and yields pole cover shapes that give rise to a magnetic field that is uniform over a larger domain. Research limitations/implications – This increased magnetic field uniformity is obtained at the cost of a pole cover shape that differs per pole. This limitation has negligible impact on the manufacturing of the separator. The new pole cover shapes therefore lead to improved performance of the density separation. Practical implications – Due to the larger uniformity the generated field, these shapes should enable larger amounts of waste to be processed than the previous design. Originality/value – This paper treats the shapes optimization of magnetic density separators systematically and presents new shapes for the ferromagnetic poles covers.

Comparison of High Pole Number Ultra-Low Speed Generator Designs Using Slotted and Air-Gap Windings

This paper describes the simple design rules that can be used to design direct-drive brushless generators for an ocean wave device. This is a very low speed device so the pole number and diameter is very large. While these machines may be large, the pole pitch and axial length is low. The application is described and air-gap wound and slotted designs are developed and simulated using analytical and finite element analysis techniques. A 248-pole design with surface rotor magnets is developed. The machines use a substantial amount of permanent magnet material and a more compact version of the slotted machine is also developed.

Force Ripple and Magnetic Unbalance Reduction Design for Doubly Salient Permanent Magnet Linear Synchronous Motor

Permanent magnet linear synchronous motor (PMLSM) has been successfully applied in various industry fields due mainly to excellent dynamic characteristics and accurate positioning capability. However, PMLSM suffers force ripple, which deteriorates controllability, and it is often considered to be an expensive linear drive mechanism since it requires a large amount of rare-earth permanent magnet (PM) material in the stationary part. This paper introduces and analyzes a new design of winding and mover arrangement for doubly salient permanent magnet linear synchronous motor (DSPMLSM). The proposed design reduces force ripples, magnetic unbalance, and the amount of PM material used in the stationary part. Extensive finite element analysis (FEA) reveals the effectiveness of the proposed design.