Zhi Wei Lin

Development of PM Transverse Flux Motors With Soft Magnetic Composite Cores

Compared with the conventional fixed speed drive, a major factor that handicaps the wide acceptance of variable speed drive with high efficiency permanent magnet (PM) motors is its high cost. This paper presents an effort to reduce the material and manufacturing costs of PM motors by using the soft magnetic composite (SMC), and the highly matured powder metallurgic technology. Because the SMCs magnetic properties are quite different from that of the traditional silicon steel sheets, special efforts have been made on measurement and modelling of vectorial magnetic properties, electrical machine topologies, and drive schemes in order to make the best use of the material. Various PM SMC motors of transverse flux topologies have been designed, fabricated, and tested. The detailed results are presented and discussed.

Measurement of magnetic properties under 3-D magnetic excitations

In a magnetic material, even under an alternating or a two-dimensional rotating magnetic excitation, the magnetic flux is three dimensional (3-D) due to the rotation of magnetic domains. For measurement of 3-D magnetic properties of materials, a novel tester has been developed. The test principle, construction, and calibration of the 3-D magnetic property tester will be presented. Experimental results of B and H loci and core losses with 3-D magnetic fluxes are included and discussed. The system is working and the results are validated.

Design and Analysis of a High-Speed Claw Pole Motor With Soft Magnetic Composite Core

Soft magnetic composite (SMC) material is formed by surface-insulated iron powder particles, generating unique properties like magnetic and thermal isotropy, and very low eddy currents. This paper presents the design and analysis of a high-speed claw pole motor with an SMC stator core for reducing core losses and cost. The analyses of magnetic and thermal fields are conducted based on a comprehensive understanding of the property of SMC materials. The 3-D finite-element analysis (FEA) is performed for accurate parameter calculation, design optimization, and thermal calculation. Because of the importance of core loss in high-speed motors, rotational core loss model is employed, and the core losses are coupled directly into thermal calculation by keeping the same hexahedral mesh structure between magnetic field analysis and thermal analysis. Since the rotor modal analysis is very important to high-speed motors, the natural frequencies and mode of the rotor are studied

Core Loss Calculation for Soft Magnetic Composite Electrical Machines

Soft magnetic composite (SMC) materials are especially suitable for developing electrical machines with complex structure and three-dimensional (3-D) magnetic flux path. In these SMC machines, the magnetic field is in general 3-D and rotational, so the mechanism and calculation of core loss may be quite different from that in traditional electrical machines with laminated steels in which the magnetic field is restrained. This paper investigates the calculation of core loss in a permanent magnet claw pole motor with SMC stator core. First, core loss models are developed based on the experimental data on SMC samples by using a 3-D magnetic property tester. Then, 3-D magnetic time-stepping field finite element analysis (FEA) is conducted to find the flux density locus in each element when the rotor rotates. The core loss is computed based on the magnetic field FEA results by using the developed core loss models. The calculations agree well with the experimental measurements on the SMC motor prototype.

Magnetic flux penetration in polycrystalline SmFeO0.75F0.2As

The recently discovered Fe–As superconducting materials which show high potential ability to carry current due to their low anisotropy have attracted a great number of attentions to understand their superconductivity mechanism and explore their applications. This paper presents a method to synthesis SmFeO0.75F0.20As polycrystalline by hot press in detail. The magnetization at different temperatures and applied fields obtained by a superconducting quantum interference device are also discussed. In addition, the local magnetization process is presented by magneto-optical imaging technique at the conditions of zero-field-cooling and field-cooling. It is found that the collective magnetization process of the newly discovered Fe–As superconductors is very similar to that of high-Tc cuprates. For instance, the Fe–As superconductors and high-Tc cuprates have the same magnetization features due to strong pining and intergrain weak link. The global supercurrent is significantly lower than local grain supercurrent ...

An amorphous alloy core medium frequency magnetic-link for medium voltage photovoltaic inverters

The advanced magnetic materials with high saturation flux density and low specific core loss have led to the development of an efficient, compact, and lightweight multiple-input multiple-output medium frequency magnetic-link. It offers a new route to eliminate some critical limitations of recently proposed medium voltage photovoltaic inverters. In this paper, a medium frequency magnetic-link is developed with Metglas amorphous alloy 2605S3A. The common magnetic-link generates isolated and balanced multiple DC supplies for all of the H-bridge inverter cells of the medium voltage inverter. The design and implementation of the prototype, test platform, and the experimental test results are analyzed and discussed. The medium frequency non-sinusoidal excitation electromagnetic characteristics of alloy 2605S3A are also compared with that of alloy 2605SA1. It is expected that the proposed new technology will have great potential for future renewable power generation systems and smart grid applications.

A Miniature Short Stroke Linear Actuator—Design and Analysis

We report a newly developed miniature short stroke tubular linear permanent-magnet actuator for robotic applications. Compared to a rotary-to-linear mechanism, the linear actuator has the advantages of efficiency, thrust control, and compact size in generating linear motion. We optimized the electromagnetic force of the actuator analytically by selecting appropriate dimensions and then predicted the force produced by the winding currents by the finite-element method under the brushless dc excitation scheme. We analyzed the actuation performance by dynamic modeling of the actuator. We constructed and tested a prototype on a specially designed test bench to verify the design. Finally, we analyzed and measured the end effect on the magnetic force due to the limited length of the stator core and translator.

Measurement of Soft Magnetic Composite Material Using an Improved 3-D Tester With Flexible Excitation Coils and Novel Sensing Coils

In this paper, accurate measurement of three dimensional (3-D) magnetic properties of soft magnetic composite (SMC) material is carried out by using an improved 3-D tester with adjustable excitation coils and novel sensing coils attached upon the surface of the SMC specimen. Comparing with the conventional 3-D tester operating at 50 Hz, the improved 3-D tester enables measurements over wide frequency range from 2 Hz to 1000 Hz. The relationships between the B vector and H vector are measured under both alternating and rotating flux conditions, and the core loss features are analyzed. These experimental results are crucial for designing new SMC electrical machines, which are expected to operate at 200 Hz or above.

Robust Optimization in HTS Cable Based on Design for Six Sigma

The nonuniform ac current distribution among the multilayer conductors in a high-temperature superconducting (HTS) cable reduces the current capacity and increases the ac loss. Various numerical simulation techniques and optimization methods have been applied in structural optimization of HTS cables. While the existence of fluctuation in design variables or operation conditions has a great influence on the cable quality, in order to eliminate the effects of parameter perturbations in design and to improve the design efficiency, a robust optimization method based on design for six sigma (DFSS) is presented in this paper. The optimization results show that the proposed optimization procedure can not only achieve a uniform current distribution, but also improve significantly the reliability and robustness of the HTS cable quality, comparing with those by using the particle swarm optimization.

Improved measurement with 2-D rotating fluxes considering the effect of internal field

This paper analyzes the effect of the internal field on the measurement with two-dimensional (2-D) rotating fluxes. It is demonstrated that due to the effect of the internal field, the misalignment of H sensing coils, causing the asymmetry of H loci and the discrepancy of the rotational core losses between two opposite rotating directions cannot be corrected completely. A numerical averaging method is employed to eliminate the angular error. Finally, the B and H loci and rotational core losses of a soft magnetic composite (SMC) material were measured under circular rotating magnetic flux density vectors, and the results were corrected by the proposed averaging method.