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Article
Publication date: 1 February 2004

I. Gurappa

This paper describes the effect of alloying elements such as Nb and Ga on the corrosion behaviour of Nd‐Fe‐B permanent magnetic alloy. The results revealed that the alloying…

Abstract

This paper describes the effect of alloying elements such as Nb and Ga on the corrosion behaviour of Nd‐Fe‐B permanent magnetic alloy. The results revealed that the alloying elements are not helpful in improving the corrosion resistance of the base magnet; rather their presence makes the base alloy highly vulnerable to corrosion in acidic environments. In particular, Nb addition is more detrimental to corrosion as was evidenced by potentiodynamic, cyclic polarisation, Ecorr vs time, electrochemical impedance and SEM results. The studies also showed that the degradation of the alloys with and without alloying addition takes place due to preferential dissolution of grain boundaries.

Details

Anti-Corrosion Methods and Materials, vol. 51 no. 1
Type: Research Article
ISSN: 0003-5599

Keywords

Article
Publication date: 10 August 2021

Zhihua Hu

The microstructure and properties of Zn-Sn coating on sintered Nd-Fe-B magnets were investigated by the grain boundary diffusion process, to improve the corrosion resistance of…

Abstract

Purpose

The microstructure and properties of Zn-Sn coating on sintered Nd-Fe-B magnets were investigated by the grain boundary diffusion process, to improve the corrosion resistance of magnet surface and explore the feasibility of realizing the lower-temperature grain boundary diffusion.

Design/methodology/approach

The Zn-Sn coating was deposited on sintered Nd-Fe-B magnets by magnetron sputtering, and then the Zn-Sn coated magnets were put into the vacuum tube furnace for grain boundary diffusion process. The morphology and structure of Zn-Sn coating as well as its mechanical properties and corrosion resistance were investigated.

Findings

Results showed that the particle size of vacuum diffusion-treated Zn-Sn coating increased and the particle agglomeration was weakened with increasing diffusion temperature, and the non-vacuum diffusion-treated Zn-Sn coating was oxidized to generate SnO2 and ZnO compounds. The binding force of coating first increased and then decreased with increasing diffusion temperature, and the maximum binding force was obtained at 540 °C. The binding force and corrosion resistance of non-vacuum diffusion-treated Zn-Sn coating were higher than the vacuum diffusion-treated Zn-Sn coating at the same diffusion temperature.

Originality/value

The Zn-Sn coating after diffusion treatment can provide complete protection, and the coating elements diffusion can be carried out at the same temperature as the secondary aging of sintered Nd-Fe-B magnets. Simultaneously, further diffusion process optimization needs to be completed because the diffusion depth is very low and only about 10 µm, which does not meet the requirements of traditional grain boundary diffusion method.

Details

Anti-Corrosion Methods and Materials, vol. 68 no. 4
Type: Research Article
ISSN: 0003-5599

Keywords

Article
Publication date: 1 January 2012

Juan Dixon, Lorenzo Urrutia, Matías Rodríguez and Rodrigo Huerta

This paper is devoted to the investigation of position estimation for a brushless DC machine using only their stator currents. The first application is for a hybrid electric…

Abstract

Purpose

This paper is devoted to the investigation of position estimation for a brushless DC machine using only their stator currents. The first application is for a hybrid electric vehicle, where the generator will be used as a motor to start the internal combustion engine (ICE).

Design/methodology/approach

This paper describes how to estimate the rotor position of a brushless DC (BLDC). Two different strategies, both based on stator currents, will be used: one for low speeds to start the ICE, and one for normal speeds for future applications in a pure electric vehicle (EV). The first one uses an estimation method based on core saturation and the second one is based on the determination of the current slopes on two of the three phases. The algorithms proposed neither needs to measure any machine parameters, nor the back emf. The methods use the information contained in the current magnitudes and slopes, and the machine mechanical speed. The system was implemented using a Digital Signal Processor (TMS320F241), which controls the phase currents and makes all the calculations required for position estimation. Additionally, the PWM signals are transmitted through a fiber optic link to minimize noise production and error on commutations.

Findings

The papers shows how an internal combustion engine can start using this approach in a brushless motor and keep it synchronized.

Research limitations/implications

This work is being applied to a hybrid electric vehicle.

Originality/value

The paper proposes a new way to start the internal combustion engine for hybrid vehicle applications through the estimation of the magnet's position. It also shows a way to estimate the position at other speeds for battery charging of the vehicle.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 31 no. 1
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 15 November 2011

Norio Takahashi, Hirofumi Shinagawa, Daisuke Miyagi and Yuhito Doi

The purpose of this paper is to examine the mechanism of the increase or decrease of eddy current loss of the segmented Nd‐Fe‐B sintered magnets without insulation, and the…

Abstract

Purpose

The purpose of this paper is to examine the mechanism of the increase or decrease of eddy current loss of the segmented Nd‐Fe‐B sintered magnets without insulation, and the effects of parameters on such a phenomenon are discussed.

Design/methodology/approach

The measured contact resistance is used in the finite element analysis.

Findings

It is shown that the eddy current loss in a magnet shows the peak value when the number of segments are increased at 40 kHz, but this property is changed at low frequency (10 kHz). Its tendency is changed by the contact resistance and the permeance (surrounding iron core).

Originality/value

The reason of a curious property of eddy current loss of segmented magnets is clearly explained by examining the eddy current distribution at various contact resistances.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 30 no. 6
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 16 March 2011

B. Ślusarek and M. Przybylski

The paper deals with methods of tailoring magnetic properties of soft and hard magnetic composites. Comparison of magnetic properties of injection moulding and compression…

Abstract

The paper deals with methods of tailoring magnetic properties of soft and hard magnetic composites. Comparison of magnetic properties of injection moulding and compression moulding Nd-Fe-B magnets are presented. Magnetic properties of Nd-Fe-B bonded magnets were tailored by different ways such as: amount of resin, addition of barium ferrite, Al or Fe powders. Influence of technological parameters such as compression pressure, time and temperature of curing on magnetic parameters of Nd-Fe-B bonded magnets are presented in the paper. Magnetic properties of soft magnetic composites made of Fe, Ni, Co are presented in the paper. Influence of technological parameters such as compression pressure, time and temperature of curing on magnetic parameters of iron soft magnetic composites are presented also in the paper.

Details

World Journal of Engineering, vol. 8 no. 1
Type: Research Article
ISSN: 1708-5284

Keywords

Article
Publication date: 1 April 1995

K. Muramatsu, T. Nakata, N. Takahashi, K. Fujiwara and H. Ukita

Recently, rare earth magnets with high coercive force such as Nd‐Fe‐B magnets have been developed. When the magnetic characteristic (M‐H curve) of such a strong magnet is…

Abstract

Recently, rare earth magnets with high coercive force such as Nd‐Fe‐B magnets have been developed. When the magnetic characteristic (M‐H curve) of such a strong magnet is measured, the conventional closed magnetic circuit method using an electromagnet cannot be applicable due to the magnetic saturation of the yoke. Therefore, the open magnetic circuit method has been proposed in which high magnetic fields are generated by using a superconducting or a pulsed magnet. In this method, the correction for demagnetizing field is required. The correction can be done using the demagnetizing factor which is a function of the shape and M‐H curve. The conventional studies take into account only the shape.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 14 no. 4
Type: Research Article
ISSN: 0332-1649

Article
Publication date: 1 June 2005

N. Takahashi, A. Fukum and D. Miyagi

In this paper, a new method for estimating iron loss under a distorted elliptical rotating flux is proposed.

Abstract

Purpose

In this paper, a new method for estimating iron loss under a distorted elliptical rotating flux is proposed.

Design/methodology/approach

In order to precisely analyze the iron loss of rotating machines, the iron loss under distorted rotating flux should be taken into account. However, reports of precise analysis considering measured iron loss data under rotating flux are few.

Findings

The iron loss of surface permanent magnet (SPM) motor model proposed by the investigation committee of IEE of Japan is estimated using the proposed method. The experimental examination is carried out by measuring the iron loss of the motor using a torque meter.

Originality/value

Examines an estimation method of iron loss of motors.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 24 no. 2
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 7 November 2016

Hongbo Qiu, Wenfei Yu, Bingxia Tang, Weili Li, Cunxiang Yang and Yanfeng Wang

Taking a 2,000 r/min 10 kW permanent magnet motor as an example, the purpose of this paper is to study the influence of driving modes on the performance of permanent magnet motor…

Abstract

Purpose

Taking a 2,000 r/min 10 kW permanent magnet motor as an example, the purpose of this paper is to study the influence of driving modes on the performance of permanent magnet motor at limit conditions, and researched the variation mechanism of motor performance influenced by different driving modes.

Design/methodology/approach

A two-dimensional electromagnetic field model of the permanent magnet motor was established, and a rectangular-wave driving circuit was built. By using the finite element method, the electromagnetic field, current, harmonic content and eddy current loss were calculated when the motor operated at rated load and limit load. On the basis of the motor loss calculation, the temperature field of the motor operating at rated condition and limit condition was researched, and the factors that influence motor limit overload capacity were analyzed. By analyzing the motor loss variation at different load conditions, the change mechanism of the motor temperature field was determined further. Combined with the related experiments, the correctness of the above analysis was verified.

Findings

Permanent magnet synchronous motor (PMSM) driven by sine wave is better compared with brushless direct current motor (BLDCM) driven by rectangular wave in reducing the magnetic field harmonics, motor losses and optimizing the temperature distribution in the motor. The method driven by sine wave could improve the motor output performance including the motor efficiency and the motor overload capacity. The winding temperature is the most important factor that limits the output capability of PMSM operating for a long time. However, because of the large rotor eddy current losses, the permanent magnet temperature is the most important factor that limits the output capability of BLDCM operating for a long time.

Practical implications

The influence of driving modes on the motor magnetic field, losses and temperature distribution, efficiency and overload capacity was determined, and the influence mechanism was also analyzed. Combined with the analysis of the electromagnetic and temperature fields, the advantages of different driving modes were presented. This study could provide an important basis for the design of permanent magnet motors with different driving modes, and it also provides reference for the application of permanent magnet motor.

Originality/value

This paper presents the influence of driving modes on permanent magnet motors. The limit output capacity of the motor with different driving modes was studied, and the key factors limiting the motor output capability were obtained.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 35 no. 6
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 29 March 2021

Martin Christopher Mapley, Geoff Tansley, Jo P. Pauls, Shaun D. Gregory and Andrew Busch

Additive manufacturing (AM) techniques have been developed to rapidly produce custom designs from a multitude of materials. Bonded permanent magnets (PMs) have been produced via…

Abstract

Purpose

Additive manufacturing (AM) techniques have been developed to rapidly produce custom designs from a multitude of materials. Bonded permanent magnets (PMs) have been produced via several AM techniques to allow for rapid manufacture of complex geometries. These magnets, however, tend to suffer from lower residual induction than the industry standard of injection moulding primarily due to the lower packing density of the magnetic particles and secondly due to the feedstock consisting of neodymium-iron-boron (Nd-Fe-B) powder with isotropic magnetic properties. As there is no compaction during most AM processes, increasing the packing density is very difficult and therefore the purpose of this study was to increase the magnetic properties of the PMs without increasing the part density.

Design/methodology/approach

Accordingly, this research investigates the use of anisotropic NdFeB feedstock coupled with an in-situ alignment fixture into an AM process known as selective laser sintering (SLS) to increase the magnetic properties of AM magnets. A Helmholtz coil array was added to an SLS machine and used to expose each powder layer during part fabrication to a near-uniform magnetic field of 20.4 mT prior to consolidation by the laser.

Findings

Permeagraph measurements of the parts showed that the alignment field introduced residual induction anisotropy of up to 46.4 ± 2.2% when measured in directions parallel and perpendicular to the alignment field. X-ray diffraction measurements also demonstrated a convergence of the orientation of the crystals when the magnets were processed in the presence of the alignment field.

Originality/value

A novel active alignment fixture for SLS was introduced and was experimentally shown to induce anisotropy in bonded PMs. Thus demonstrating a new method for the enhancement in energy density of PMs produced via AM methods.

Article
Publication date: 5 January 2015

Belli Zoubida and Mohamed Rachid Mekideche

Reducing eddy current losses in magnets of electrical machines can be obtained by means of several techniques. The magnet segmentation is the most popular one. It imposes the…

Abstract

Purpose

Reducing eddy current losses in magnets of electrical machines can be obtained by means of several techniques. The magnet segmentation is the most popular one. It imposes the least restrictions on machine performances. This paper investigates the effectiveness of the magnet circumferential segmentation technique to reduce these undesirable losses. The full and partial magnet segmentation are both studied for a frequency range from few Hz to a dozen of kHz. To increase the efficiency of these techniques to reduce losses for any working frequency, an optimization strategy based on coupling of finite elements analysis and genetic algorithm is applied. The purpose of this paper is to define the parameters of the total and partial segmentation that can ensure the best reduction of eddy current losses.

Design/methodology/approach

First, a model to analyze eddy current losses is presented. Second, the effectiveness of full and partial magnet circumferential segmentation to reduce eddy loss is studied for a range of frequencies from few Hz to a dozen of kHz. To achieve these purposes a 2-D finite element model is developed under MATLAB environment. In a third step of the work, an optimization process is applied to adjust the segmentation design parameters for best reduction of eddy current losses in case of surface mounted permanent magnets synchronous machine.

Findings

In case of the skin effect operating, both full and partial magnet segmentations can lead to eddy current losses increases. Such deviations of magnet segmentation techniques can be avoided by an appropriate choice of their design parameters.

Originality/value

Few works are dedicated to investigate partial magnet segmentation for eddy current losses reduction. This paper studied the effectiveness and behaviour of partial segmentation for different frequency ranges. To avoid eventual anomalies related to the skin effect an optimization process based on the association of the finite elements analysis to genetic algorithm method is adopted.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 34 no. 1
Type: Research Article
ISSN: 0332-1649

Keywords

1 – 10 of 43