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Article
Publication date: 22 October 2019

Mohammed Rajik Khan and Atul Sonawane

This paper aims to present 3D finite element (FE) simulations of impact loading on a construction safety helmet over a headform to improve the ventilation slots profile in helmet…

Abstract

Purpose

This paper aims to present 3D finite element (FE) simulations of impact loading on a construction safety helmet over a headform to improve the ventilation slots profile in helmet design.

Design/methodology/approach

Impact response on headforms in three different studies considering ventilation slots of varied profiles and dimensions in helmets with rectangular elliptical and circular slots is compared and analysed. Head injury criteria (HIC) and safety regulations from past literature have been considered to evaluate the impact responses.

Findings

Simulation results show that a helmet with rectangular ventilation slots achieves a lowest peak impact force of 5941.3 N for a slot area of 170 mm2 as compared to elliptical and circular slots.

Research limitations/implications

Ventilation slots of simple geometry (rectangular, elliptical and circular) have been considered in this work. Other/complex geometry slots can also be chosen to predict its effect during impact response on a helmet–headform model. Biofidelic head–neck FE model can be developed to achieve precise results.

Practical implications

The presented work gives a clear idea to design engineers for the selection of ventilation slot profiles to design a construction safety helmet.

Social implications

Construction safety (CS) helmets are used to reduce injuries on heads of workers at construction sites in the event of free-falling objects. Rectangular ventilation slots in CS helmets as suggested in the work may reduce the risk of injury.

Originality/value

Results are found in good agreement with the past numerical simulation of impact response on a construction safety helmet over a validated biofidelic head FE model.

Details

Journal of Engineering, Design and Technology , vol. 18 no. 3
Type: Research Article
ISSN: 1726-0531

Keywords

Article
Publication date: 2 March 2015

Maria Dems, Krzysztof Komeza, Slawomir Wiak and Sara Fernández Coya

– The purpose of this paper is to present the distribution of the magnetic field and additional losses analysis of the induction motors (IM) with opened and closed rotor slots.

Abstract

Purpose

The purpose of this paper is to present the distribution of the magnetic field and additional losses analysis of the induction motors (IM) with opened and closed rotor slots.

Design/methodology/approach

In the field-circuit approach the distribution and changes of magnetic flux density in the motor are computed using a time-stepping finite element method. The additional losses in each element are evaluated at different frequencies.

Findings

An approximate analytical formulation is derived for rapid losses computation confirmed by the results of field-circuit method. For high-voltage motors due to the size ratios of the core and relatively deep stator and rotor slots major role in causing loss of higher harmonics play a fundamental slot harmonics. Higher harmonics order bigger than 100 cause only small part of total higher harmonics core losses. Closed rotor slots construction influenced significantly on no-load losses mainly due to reduction of losses at slot upper part. For nominal load condition that influence is not so strong according to the saturation of slot tips by rotor leakage flux. Nevertheless, core losses at load are several times higher as at no-load.

Research limitations/implications

In future research authors will take into account motors feed from PWM inverter, working in the frequency range up to 400 Hz.

Practical implications

The results of investigation will be used in more detailed design of IMs especially for motors with closed rotor slots.

Originality/value

The methods presented in the paper was not used before. Also results of additional losses in the motor core calculation, especially according motors with closed slots at no load and load conditions are new.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 34 no. 2
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 3 May 2013

Liang Yan‐ping, Yu Hong‐hao and Bian Xu

The purpose of this paper is to introduce an analytic method to calculate the slot leakage reactance of stator bar strands in alternative current machines whose stator windings…

Abstract

Purpose

The purpose of this paper is to introduce an analytic method to calculate the slot leakage reactance of stator bar strands in alternative current machines whose stator windings have multiple bars per layer and using deficient transposition.

Design/methodology/approach

Based on the analysis of deficient transposition, the calculation model of mutual slot leakage reactance between any two strands in one bar is established. The subsection integral method is presented to calculate the slot leakage reactance and analytic function is listed. A pump motor used in nuclear power is taken as an example, and the slot self leakage reactance of any strand in its top layer winding and the slot mutual leakage reactance between one strand and other strands in the same bar are calculated depending on the method described above. The slot leakage reactance of all strands in the top layer winding is calculated when different transposition angles are applied in stator bars.

Findings

The results show that subsection integral method is effective in calculating the slot leakage reactance of stator bar strands of deficient transposition. The slot leakage reactance distribution of all strands is obtained. The transposition angle has a great impact on the slot leakage reactance distribution of stator bar strands.

Originality/value

This paper presents an available method to calculate the slot leakage reactance of any strands in alternative current machine whose stator windings have multiple bars per layer and using deficient transposition, and discusses the impact of transposition angle on the slot leakage reactance. The conclusion can lay the foundation of the effective calculation of circulating current losses in stator bars with deficient transposition.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 32 no. 3
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 5 May 2015

Stefan Schmülling and Stefan Kulig

Magnetic slot wedges are usually installed in open slot high-voltage induction machines. They reduce the no load losses and the magnetization current. Additionally, the leakage…

Abstract

Purpose

Magnetic slot wedges are usually installed in open slot high-voltage induction machines. They reduce the no load losses and the magnetization current. Additionally, the leakage inductance increases. However, machines and the slot wedges are getting frequently damaged with a decreasing maintenance interval. The usage of magnetic slot wedges leads to unknown effects. It is possible, that direct magnetic forces or indirect forces, caused by the deformation of the stator or stator teeth during operation, results in the damage of the slots wedges. The purpose of this paper is to fully understand the influence of the magnetic slot wedges and the intrinsic effects.

Design/methodology/approach

A finite element model of the affected machine is verified with current and torque values from the data sheet of the affected machine. Three types of forces, which are working on the slot wedges, are considered and compared.

Findings

There are direct forces working on the slot wedges. The origin of this forces and a coherence between this forces and the slot number relationship, between stator and rotor slots is shown as well as reasons for the damage to the slot wedges.

Originality/value

There are investigations about the influence of the behaviour of an induction machine by magnetic slot wedges. This investigations consider the influence on the network models of such machines. The paper at hand deals with the intrinsic effects caused by the slot wedges and its consequences.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 34 no. 3
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 21 July 2020

Hongbo Qiu, Xutian Zou and Xiaobin Fan

Owing to the salient pole structure and stator slots of hydro-generator, the air gap magnetic field in the generator is unevenly distributed. High-frequency harmonic components…

Abstract

Purpose

Owing to the salient pole structure and stator slots of hydro-generator, the air gap magnetic field in the generator is unevenly distributed. High-frequency harmonic components contained in the inhomogeneous air gap magnetic field will have a negative impact on the generator performance. The purpose of this paper, therefore, is to improve the distribution of air gap magnetic field by using appropriate magnetic slot wedge, thereby improving the generator performance.

Design/methodology/approach

Taking a 24 MW, 10.5 kV bulb tubular turbine generator as an example, the 2 D electromagnetic field model of the generator is established by finite element method. The correctness of the model is verified by comparing the finite element calculation data with the experimental data. The influences of the permeability and thickness of the magnetic slot wedge on the generator performance are studied.

Findings

It is found that the intensity and harmonic content of the air gap magnetic field will change with the permeability of slot wedge and then the performance parameters of the generator will also change nonlinearly. The relationship between the eddy current loss, torque ripple, output voltage and other parameters of the generator and the permeability of slot wedge is confirmed. In addition, the variation of losses and torque with wedge thickness is also obtained.

Originality/value

The influence mechanism of magnetic slot wedge on the performance of hydro-generator is revealed. The presented results give guidelines to selecting suitable magnetic slot wedge to improve generator performance.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering , vol. 39 no. 4
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 13 November 2009

Ayman M. EL‐Refaie, Z.Q. Zhu, Thomas M. Jahns and David Howe

Permanent magnet (PM) brushless machines equipped with fractional‐slot concentrated‐windings (FSCW) have been receiving considerable attention over the past few years, due to the…

1094

Abstract

Purpose

Permanent magnet (PM) brushless machines equipped with fractional‐slot concentrated‐windings (FSCW) have been receiving considerable attention over the past few years, due to the fact that they have short end‐windings, a high‐slot fill factor, a high efficiency and power density, and good flux‐weakening and fault‐tolerance capabilities. A key design parameter for such machines is the phase winding inductance since this has a significant impact on the performance, as well as on the magnitude of any reluctance torque. The purpose of this paper is to describe a detailed investigation of the various components of the winding inductance in machines equipped with both overlapping and non‐overlapping windings and different slot/pole number combinations. It also examines the influence of key design parameters, which affect the inductance components, with particular reference to the inductances of machines in which all the teeth are wound and those in which only alternate teeth are wound.

Design/methodology/approach

The paper analyzes and compares various inductance components which result from different winding configurations.

Findings

It is shown that the main component of the winding inductance is the relatively large slot‐leakage component. Both analytical and finite element models are employed and predicted results are validated on several prototype machines.

Originality/value

Such a thorough investigation of the various inductance components for these type of machines has not been presented before. The paper will serve as a good reference for engineers and researchers designing PM machines equipped with FECW.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 28 no. 6
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 1 January 2013

Imen Abdennadher and Ahmed Masmoudi

The paper is aimed at the investigation of the magnetic forces generated by fractional slot surface mounted PM machines, considering a comparative study between two topologies: a…

Abstract

Purpose

The paper is aimed at the investigation of the magnetic forces generated by fractional slot surface mounted PM machines, considering a comparative study between two topologies: a 9 slot/10 pole machine and a 12 slot/10 pole machine.

Design/methodology/approach

Following the distribution of the armature windings using the star of slots approach, an investigation of the magnetic forces developed by both machines under study, using 3D finite element analysis (FEA). Prior to such investigation, a 2D FEA based sizing procedure is carried out in order to select a set of suitable geometrical parameters. Then, the comparison between both machines is extended to the torque production capability.

Findings

It has been found that the 9 slot/10 pole machine has a pic value of the average magnetic force reaching almost 40N which is located in one side of the air gap. Such a peak does not exceed 7N in the 12 slot/10 pole machine and is located in two diametrically‐opposite areas of the air gap.

Research limitations/implications

This work should be extended by an experimental validation of the FEA results regarding the magnetic force generation.

Practical implications

The list of the selection criteria of fractional slot PM machines should be extended to the magnetic force generation in order to fulfil the requirements of many applications such as the propulsion systems.

Originality/value

The paper proposes a combined electromagnetic‐mechanical approach to investigate the magnetic forces generated by fractional slot surface mounted PM machines using 2D and 3D finite element analysis.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 32 no. 1
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 10 February 2023

Huiyong Wang, Ding Yang, Liang Guo and Xiaoming Zhang

Intent detection and slot filling are two important tasks in question comprehension of a question answering system. This study aims to build a joint task model with some…

Abstract

Purpose

Intent detection and slot filling are two important tasks in question comprehension of a question answering system. This study aims to build a joint task model with some generalization ability and benchmark its performance over other neural network models mentioned in this paper.

Design/methodology/approach

This study used a deep-learning-based approach for the joint modeling of question intent detection and slot filling. Meanwhile, the internal cell structure of the long short-term memory (LSTM) network was improved. Furthermore, the dataset Computer Science Literature Question (CSLQ) was constructed based on the Science and Technology Knowledge Graph. The datasets Airline Travel Information Systems, Snips (a natural language processing dataset of the consumer intent engine collected by Snips) and CSLQ were used for the empirical analysis. The accuracy of intent detection and F1 score of slot filling, as well as the semantic accuracy of sentences, were compared for several models.

Findings

The results showed that the proposed model outperformed all other benchmark methods, especially for the CSLQ dataset. This proves that the design of this study improved the comprehensive performance and generalization ability of the model to some extent.

Originality/value

This study contributes to the understanding of question sentences in a specific domain. LSTM was improved, and a computer literature domain dataset was constructed herein. This will lay the data and model foundation for the future construction of a computer literature question answering system.

Details

Data Technologies and Applications, vol. 57 no. 5
Type: Research Article
ISSN: 2514-9288

Keywords

Article
Publication date: 13 December 2022

Kejia Chen, Jintao Chen, Lixi Yang and Xiaoqian Yang

Flights are often delayed owing to emergencies. This paper proposes a cooperative slot secondary assignment (CSSA) model based on a collaborative decision-making (CDM) mechanism…

Abstract

Purpose

Flights are often delayed owing to emergencies. This paper proposes a cooperative slot secondary assignment (CSSA) model based on a collaborative decision-making (CDM) mechanism, and the operation mode of flight waves designs an improved intelligent algorithm to solve the optimal flight plan and minimize the total delay of passenger time.

Design/methodology/approach

Taking passenger delays, transfer delays and flight cancellation delays into account comprehensively, the total delay time is minimized as the objective function. The model is verified by a linear solver and compared with the first come first service (FCFS) method to prove the effectiveness of the method. An improved adaptive partheno-genetic algorithm (IAPGA) using hierarchical serial number coding was designed, combining elite and roulette strategies to find pareto solutions.

Findings

Comparing and analyzing the experimental results of various scale examples, the optimization model in this paper is greatly optimized compared to the FCFS method in terms of total delay time, and the IAPGA algorithm is better than the algorithm before in terms of solution performance and solution set quality.

Originality/value

Based on the actual situation, this paper considers the operation mode of flight waves. In addition, the flight plan solved by the model can be guaranteed in terms of feasibility and effectiveness, which can provide airlines with reasonable decision-making opinions when reassigning slot resources.

Details

International Journal of Intelligent Computing and Cybernetics, vol. 16 no. 2
Type: Research Article
ISSN: 1756-378X

Keywords

Article
Publication date: 7 March 2016

Y. Oner, Z.Q. Zhu, L.J. Wu and X. Ge

Due to high electromagnetic torque at low speed, vernier machines are suitable for direct-drive applications such as electric vehicles and wind power generators. The purpose of…

Abstract

Purpose

Due to high electromagnetic torque at low speed, vernier machines are suitable for direct-drive applications such as electric vehicles and wind power generators. The purpose of this paper is to present an exact sub-domain model for analytically predicting the open-circuit magnetic field of permanent magnet vernier machine (PMVM) including tooth tips. The entire field domain is divided into five regions, viz. magnets, air gap, slot openings, slots, and flux-modulation pole slots (FMPs). The model accounts for the influence of interaction between PMs, FMPs and slots, and radial/parallel magnetization.

Design/methodology/approach

Magnetic field distributions for slot and air-gap, flux linkage, back-EMF and cogging torque waveforms are obtained from the analytical method and validated by finite element analysis (FEA).

Findings

It is found that the developed sub-domain model including tooth tips is very accurate and is applicable to PMVM having any combination of slots/FMPs/PMs.

Originality/value

The main contributions include: accurate sub-domain model for PMVM is proposed for open-circuit including tooth-tip which cannot be accounted for in literature; the model accounts the interaction between flux modulation pole (FMP) and slot; developed sub-domain model is accurate and applicable to any slot/FMP/PM combinations; and it has investigated the influence of FMP/slot opening width/height on cogging torque.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 35 no. 2
Type: Research Article
ISSN: 0332-1649

Keywords

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