Search results

1 – 7 of 7
To view the access options for this content please click here
Article
Publication date: 30 November 2020

Emre Uygun, Michel Hecquet, Abdelmounaïm Tounzi, Daniel Depernet, Vincent Lanfranchi, Serge Bruno and Thierry Tollance

This paper deals with the study of the influence of the phase shift between currents and back-electromotive forces (back-EMF) on torque ripple and radial magnetic forces…

Abstract

Purpose

This paper deals with the study of the influence of the phase shift between currents and back-electromotive forces (back-EMF) on torque ripple and radial magnetic forces for a low power synchronous machine supplied with 120 degrees square-wave currents. This paper aims to establish a good compromise between efficiency, harmonics of torque and harmonics of radial forces at the origin of the electromagnetic noise.

Design/methodology/approach

Based on a finite element approach, torque and magnetic pressure harmonics versus space and frequency are evaluated for different angle values. The evolutions of the different harmonics against the load angle are analyzed and compared to those of experimental measurements.

Findings

Depending on the load torque, field-weakening or field-boosting can be used to reduce current harmonics contributing the most to the radial magnetic forces responsible for the noise. Besides, a compromise can be found to avoid deteriorating too much the performances of the machine, thus being suitable with an industrial application.

Research limitations/implications

This study concerns low power permanent magnet synchronous machines with concentrated windings and driven with a trapezoidal control, while having sinusoidal back-EMF.

Originality/value

The use of a simple mean and suitable with a large-scale manufacturing industry to reduce the identified electromagnetic-borne noise of a specific electric drive makes the originality.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering , vol. 39 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

To view the access options for this content please click here
Article
Publication date: 10 July 2020

Dominique Giraud, Baptiste Ristagno, Denis Netter, Julien Fontchastagner, Nicolas Labbe and Vincent Lanfranchi

This paper aims to propose a method to evaluate the information obtained on harmonics calculations and to estimate the precision of results using finite element method for…

Abstract

Purpose

This paper aims to propose a method to evaluate the information obtained on harmonics calculations and to estimate the precision of results using finite element method for an innovative motor topology in which some well-known meshing rules are difficult to apply.

Design/methodology/approach

The same magnetostatic problem is solved with several mesh sizes using both scalar and vector potentials magnetics formulations on a complex topology, an axial claw pole motor (ACPM). The proposed method lies in a comparison between the two weak formulations to determine what information is obtained on harmonics calculations and to estimate its precision. Moreover, an original mesh method is applied in the air gap to improve the numerical results.

Findings

The precision on harmonics calculations using finite element method on an ACPM is estimated. For the proposed motor and mesh, only the mean value (even with large mesh) and the first harmonic (with fine mesh) of torque are calculated with a good accuracy. This results confirm that the non-respect of the meshing rules have a strong impact on the results and that scalar and vector potentials magnetics formulations do not give exactly the same results. Before using torque harmonics values in vibration calculations, a finite element model has to be validated by using both fomulations.

Research limitations/implications

This method is time-consuming and only applied on an ACPM in this work.

Originality/value

The axial claw pole motor, for which the classic meshing rules cannot be applied, is a complex topology very under-studied. To improve the calculation of space harmonics, the authors proposed to split the airgap into four parts. Then in the two central parts, the meshing step of the structured mesh is equal to the rotating step.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering , vol. 39 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

To view the access options for this content please click here
Article
Publication date: 7 November 2016

Bruno Iamamura, Mathieu Rossi, Michel Hecquet, Vincent Lanfranchi, Sylvain Recorbet and Florence Tridon

The purpose of this paper is to present an original study of industrial inductors with different air-gap materials in order to reduce the vibration and noise of inductors…

Abstract

Purpose

The purpose of this paper is to present an original study of industrial inductors with different air-gap materials in order to reduce the vibration and noise of inductors. Acoustic comfort is an increasingly important factor at the design stage of industrial inductors associated to converters. In addition, power converters in the railway domain are more and more compact and powerful.

Design/methodology/approach

Experiments, simulations and test devices were used to determine the main physical phenomena that generate the undesirable audible noise. Electric and vibratory measurements (modal and operational analysis) were compared with the numerical calculations. PWM and sinusoidal supply were taken into account and different prototypes with different materials in the air-gap were built.

Findings

This study analyzes and details the origin of the electromagnetic noise due to the vertical mode, in order to reduce the vibration and noise of inductors. A detailed analysis using finite element simulation and experimental measurements of free-free mode or forced mode under electrical excitation was conducted to interpret the vibrations of the structure. In addition, in order to observe trends and the impact of magnetostriction effect, the authors propose a simplified model.

Practical implications

Electric and vibratory measurements (modal and operational analysis) are compared with the numerical calculations.

Originality/value

This paper gives a response about the origin of the noise with different experimental measurements. Changing the air-gap material is beneficial for the deflection of the inductor. However, it has been presented that, following the shape of the inductor, it is beneficial to reduce or increase the stiffness of the material depending on the column height. For a fixed Young’s modulus air-gap, a ratio Column height/air-gap thickness exists, which makes it possible to cancel the deflection.

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

To view the access options for this content please click here
Article
Publication date: 12 September 2008

Jean Le Besnerais, Vincent Lanfranchi, Michel Hecquet, Pascal Brochet and Guy Friedrich

The purpose of this paper is to apply a fast analytical model of the acoustic behaviour of pulse‐width modulation (PWM) controlled induction machines to a fractional‐slot…

Abstract

Purpose

The purpose of this paper is to apply a fast analytical model of the acoustic behaviour of pulse‐width modulation (PWM) controlled induction machines to a fractional‐slot winding machine, and to analytically clarify the interaction between space harmonics and time harmonics in audible electromagnetic noise spectrum.

Design/methodology/approach

A multilayer single‐phase equivalent circuit calculates the stator and rotor currents. Air‐gap radial flux density, which is supposed to be the only source of acoustic noise, is then computed with winding functions formalism. Mechanical and acoustic models are based on a 2D ring stator model. A method to analytically derive the orders and frequencies of most important vibration lines is detailed. The results are totally independent of the supply strategy and winding type of the machine. Some variable‐speed simulations and tests are run on a 700 W fractional‐slot induction machine in sinusoidal case as a first validation of theoretical results.

Findings

The influence of both winding space harmonics and PWM time harmonics on noise spectrum is exposed. Most dangerous orders and frequencies expressions are demonstrated in sinusoidal and PWM cases. For traditional integral windings, it is shown that vibration orders are necessarily even. When the stator slot number is not even, which is the case for fractional windings, some odd order deflections appear: the radial electromagnetic power can therefore dissipate as vibrations through all stator deformation modes, leading to a potentially lower noise level at resonance.

Research limitations/implications

The analytical research does not consider saturation and eccentricity harmonics which can play a significant role in noise radiation.

Practical implications

The analytical model and theoretical results presented help in designing low‐noise induction machines, and diagnosing noise or vibration problems.

Originality/value

The paper details a fully analytical acoustic and electromagnetic model of a PWM fed induction machine, and demonstrate the theoretical expression of main noise spectrum lines combining both time and space harmonics. For the first time, a direct comparison between simulated and experimental vibration spectra is made.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 27 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

To view the access options for this content please click here
Article
Publication date: 3 April 2017

Marine Coupaud

Workers’ health is a main concern in industrialized countries. The structural evolution of the labor market should have encouraged better working conditions, as should…

Abstract

Purpose

Workers’ health is a main concern in industrialized countries. The structural evolution of the labor market should have encouraged better working conditions, as should have increasing interest in corporate social responsibility. But work arduousness takes new forms as work organizations evolve. All workers are potentially affected by onerous working conditions. The purpose of this paper is to explore all types of working conditions that may affect workers.

Design/methodology/approach

The author creates four indicators of working conditions using the multiple correspondence analysis and also analyzes how they relate to the workers’ physical and mental health using a logit model.

Findings

Performing the analysis on data from the third and fifth waves of the European Working Conditions Survey, the author presents the results showing the growing importance of interpersonal relationships at work and observes a rise in inequalities in terms of health over the period 2000-2010 for people belonging to the vulnerable categories: women and lower-income groups.

Originality/value

The author offers to describe the evolution of the working conditions of the European workers over an interesting period during which many changes took place. Moreover, this paper investigates the respective impacts of different types of working conditions to come up with policy recommendations.

Details

International Journal of Manpower, vol. 38 no. 1
Type: Research Article
ISSN: 0143-7720

Keywords

To view the access options for this content please click here
Article
Publication date: 9 November 2020

Harrison Esam Awuh and Marleen Dekker

Building on the limitations of the efforts of aid agencies and non-governmental organisations to pull the poor out of poverty in low- and middle-income countries and…

Abstract

Purpose

Building on the limitations of the efforts of aid agencies and non-governmental organisations to pull the poor out of poverty in low- and middle-income countries and declining opportunities for market expansion in high-income countries, microfranchising is being promoted as a pro-poor business model, which promotes entrepreneurship. Sub-Saharan Africa has become a fertile ground for the propagation of this model. However, contemporary studies on microfranchising have not sufficiently explored what motivates people to turn to this method of doing business.

Design/methodology/approach

Through the case of a microfranchise in Ghana (FanMilk), the purpose of this paper is to use qualitative methods to study motivations for engaging in entrepreneurship ventures in a microfranchise.

Findings

The findings reveal whether motivations for becoming microfranchise entrepreneurs change over time or are varied, and these changes are moderated by changing opportunities, challenges and demographic factors.

Originality/value

These findings contribute to knowledge on microfranchising in terms of theory, policy and practice. The findings also seek to stimulate further inquiry into microfranchising and its ability to create value for multiple parties when operating in emerging markets such as Africa.

Details

Journal of Entrepreneurship in Emerging Economies, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 2053-4604

Keywords

To view the access options for this content please click here
Article
Publication date: 25 October 2019

Jan Mei Lim

Emotion regulation is an ongoing multiprocess phenomenon and is a challenging developmental task to acquire in individuals with autism spectrum disorder (ASD) who have…

Abstract

Purpose

Emotion regulation is an ongoing multiprocess phenomenon and is a challenging developmental task to acquire in individuals with autism spectrum disorder (ASD) who have different neurobiological profiles and emotion regulation problems. The purpose of this paper is to review recent literature to understand the neurobiological and psychological perspective of emotion regulation in ASD, while converging themes of psychosocial interventions and existing best practices on emotion regulation within this heterogeneous population are reviewed and discussed in consideration of intellectual disability (ID).

Design/methodology/approach

Review of recent literature and common empirically supported interventions addressing emotional regulation implemented in individuals with and without ASD, and with and without ID were included in the electronic database search through PubMed, EBSChost, Science Direct, Wiley Online Library, GALE and SAGE. Search terms used included autism, ID, cognitive control, executive function, sensory processing/intervention, emotion regulation, cognitive behavior therapy, mindfulness, social stories, positive behavior support and behavior therapy.

Findings

Neural systems governing emotion regulation can be divided into “top-down” and “bottom-up” processing. Prefrontal cortex, cognitive and attentional control are critical for effective emotion regulation. Individuals with ASD, and with ID show impairments in these areas have problems with emotion regulation. Targeted psychosocial intervention need to consider bottom-up and top-down processes of emotion regulation, and that standardized interventions require adaptations.

Originality/value

There are limited studies looking into understanding the neurobiological and psychological perspective of emotion regulation in ASD and linking them to interventions. This review highlights psychosocial interventions that are important for further research, investigation and development as treatment in this population is limited.

1 – 7 of 7