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Open Access
Article
Publication date: 7 July 2021

Alfonso Camba-Crespo, José García-Solanes and Fernando Torrejón-Flores

This study aims to identify structural breaks in the current account and the periods between these breaks, which the authors name stability spells, and study their characteristics…

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Abstract

Purpose

This study aims to identify structural breaks in the current account and the periods between these breaks, which the authors name stability spells, and study their characteristics and determinants.

Design/methodology/approach

Using data from the IMF and the World Bank, this study applies the Lee and Strazicich test to endogenously identify breaks and the Heckman selection model to simultaneously study the determinants of structural breaks and current-account changes after breaks.

Findings

This study identifies 212 significant structural breaks and 341 stability spells. These spells become shorter and more volatile the further they are from equilibrium, and half of them last 10 years or less. The results show that economic growth and foreign-exchange piling are particularly useful to prevent breaks, while lower per capita income increases exposure to break risks.

Originality/value

This study introduces the concept of current-account stability spells to refer to the periods between structural breaks. These spells are then studied to determine their main characteristics. The authors also apply a global perspective in their analysis, using a wide sample of 181 economies between 1980 and 2018 and considering positive and negative breaks in both level and trend.

Article
Publication date: 20 September 2018

Omid Abdi Monfared, Aref Doroudi and Amin Darvishi

Squirrel cage induction motors suffer from several faults such as rotor broken bar. One of the powerful methods to detect induction motor faults is the line current signature…

Abstract

Purpose

Squirrel cage induction motors suffer from several faults such as rotor broken bar. One of the powerful methods to detect induction motor faults is the line current signature analysis. This paper aims to present a novel algorithm based on continuous wavelet transform (CWT) to diagnose a rotor broken bar fault.

Design/methodology/approach

The proposed CWT has high flexibility in monitoring any frequency of interest in a waveform. Based on this transform, stator current frequency spectrum is analyzed to diagnose the rotor broken bar fault. The algorithm distinguishes the healthy motor from the faulted one based on a proper index. The method can be used in steady-state running time of induction motor and under different loading conditions. Experimental results are presented to show the validity of the proposed approach.

Findings

The proposed index considerably increases at the broken bars conditions compared to the healthy conditions. It can clearly diagnose the faulty conditions. The experimental results are found to be in good agreement with the theoretical and simulated results. The proposed method can reduce the noise and spectral leakage effects.

Originality/value

The main contribution of the paper are as follows: using CWT for detection of broken bar faults; introducing a proper index for diagnosing broken bars; and introducing a supplementary index to reduce the noise and spectral leakage effects.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 38 no. 1
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 10 August 2023

Dahlia Robinson, Thomas Smith, James Devin Whitworth and Yiyang Zhang

This study aims to investigate whether accounting-related litigation is associated with a break in the client’s earnings string and the auditor’s response to a break in the…

Abstract

Purpose

This study aims to investigate whether accounting-related litigation is associated with a break in the client’s earnings string and the auditor’s response to a break in the earnings string.

Design/methodology/approach

The authors use regression models on a sample of publicly-traded USA companies with earnings strings.

Findings

The authors find that clients’ earnings string breaks are associated with increased accounting litigation risk and audit fees. The results are more prevalent for larger breaks.

Research limitations/implications

The findings suggest auditors anticipate string breaks by clients which implies that audit fee research should consider earnings string characteristics in the fee models.

Practical implications

The auditor’s access to private information allows them to anticipate string breaks and potential increase in litigation risk.

Originality/value

An earnings string break represents a convergence of concerns highly relevant to the auditor: more users relying on the financial statements with greater expectations, increased likelihood of losses to those users, an environment where the likelihood of misstatement may increase, and explicitly stated professional responsibilities in response to the latter. Despite that, and a rich earnings string literature, prior studies have not directly examined auditors’ response to a client’s string break.

Details

Managerial Auditing Journal, vol. 38 no. 7
Type: Research Article
ISSN: 0268-6902

Keywords

Article
Publication date: 1 July 2014

George Cairns

This paper aims to critically engage with the premise of development at the “bottom of the pyramid” through consideration of the current and potential future status of the workers…

1112

Abstract

Purpose

This paper aims to critically engage with the premise of development at the “bottom of the pyramid” through consideration of the current and potential future status of the workers who dismantle end-of-life ships in the breaking yards of “less developed countries”, here with specific reference to the dynamic situation in Bangladesh.

Design/methodology/approach

The study applies “critical scenario method” (CSM) to explore different possible and plausible futures for the ship-breaking industry globally and locally.

Findings

The paper argues that the status of the workers in the ship-breaking industry of Bangladesh can be conceptualised as firmly set at the “bottom of the pyramid”, and that, for most if not all, this situation cannot be changed within any industry future without wider, radical change to socioeconomic and political structures both in the country and globally.

Originality/value

This paper offers a contribution to the discourse on consumption at the “bottom of the pyramid” as a development process.

Details

critical perspectives on international business, vol. 10 no. 3
Type: Research Article
ISSN: 1742-2043

Keywords

Article
Publication date: 26 August 2014

Rosario Miceli, Yasser Gritli, Antonino Di Tommaso, Fiorenzo Filippetti and Claudio Rossi

The purpose of this paper is to present a diagnosis technique, for rotor broken bar in double cage induction motor, based on advanced use of wavelet transform analysis. The…

Abstract

Purpose

The purpose of this paper is to present a diagnosis technique, for rotor broken bar in double cage induction motor, based on advanced use of wavelet transform analysis. The proposed technique is experimentally validated.

Design/methodology/approach

The proposed approach is based on a combined use of frequency sliding and wavelet transform analysis, to isolate the contribution of the rotor fault components issued from vibration signals in a single frequency band.

Findings

The proposed technique is reliable for tracking the rotor fault components over time-frequency domain. The quantitative analysis results based on this technique are the proof of its robustness.

Research limitations/implications

The validity of the proposed diagnosis approach is not limited to the analysis under steady-state operating conditions, but also for time-varying conditions where rotor fault components are spread in a wide frequency range.

Practical implications

The developed approach is best suited for automotive or high power traction systems, in which safe-operating and availability are mandatory.

Originality/value

The paper presents a diagnosis technique for rotor broken bar in double cage induction motor base on advanced use of wavelet transform which allows the extraction of the most relevant rotor fault component issued from axial vibration signal and clamping it in a single frequency bandwidth, avoiding confusions with other components and false interpretations.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 33 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 6 September 2022

Lijian Quan and Guohui Zeng

In the event of a DC short-circuit fault in a flexible DC power grid, the high peak value of the fault current puts forward more stringent requirements on the DC circuit breaker…

53

Abstract

Purpose

In the event of a DC short-circuit fault in a flexible DC power grid, the high peak value of the fault current puts forward more stringent requirements on the DC circuit breaker. The existing fault current cutoff mainly focuses on changing the topology structure. To suppress the development of fault current and reduce the investment cost of the DC grid, this paper aims to propose a dual-loop active current-limiting control based on energy difference.

Design/methodology/approach

Firstly, the equivalent circuit at fault is established, and the parameters related to the fault current are analyzed. Then, the relationship between the output voltage change of the bridge arm and the difference between the AC and DC energy is deduced. Finally, the experimental results are discussed on the real-time simulation platform Opal-RT.

Findings

The proposed current-limiting measures can greatly reduce the fault current, reduce the breaking current of the circuit breaker and increase the capacitor voltage during the fault period, which is beneficial to the stability of the AC system. It is verified that the proposed method is also applicable to a certain high-resistance fault.

Originality/value

This paper applies the method of AC fault to DC fault and deduces the relationship between energy difference and voltage variation corresponding to different step lengths based on digital simulation. In addition, two variables are used as control structure parameters to reduce the probability of system misoperation.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering , vol. 42 no. 2
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 2 November 2015

Amina Mesbeh, Marwen Jarboui and Ahmed Masmoudi

The purpose of this paper is to investigate the effects of different faulty scenarios on the induction motor (IM) operation with emphasis on the currents in the rotor bar and end…

Abstract

Purpose

The purpose of this paper is to investigate the effects of different faulty scenarios on the induction motor (IM) operation with emphasis on the currents in the rotor bar and end rings.

Design/methodology/approach

The modeling of the IM followed by a graphical representation-based analysis of the rotor steady-state currents under healthy operation is treated. Then, a case study is considered in order to investigate different faulty scenarios with a focus on the rotor cage currents.

Findings

It has been found that the rotor faults greatly affect the currents in the bars and in the end rings both in amplitude and in harmonic content. These vary according to the relative positions with respect to the fault such that: the currents in the bars adjacent to the faulty one(s) have the highest amplitudes with the lowest harmonic content; and the ones in the ring portions adjacent to the faulty one have the lowest amplitudes with the highest harmonic content.

Research limitations/implications

Although the simulated model has confirmed the well known IM behavior under healthy operation, it would be appreciated if the obtained results under faulty operation would be validated by finite element analysis.

Practical implications

It is of great interest to investigate the effects of faulty scenarios on the rotor cage currents, in order to take appropriate actions starting from the design of the IM.

Originality/value

A deep investigation (including the waveforms, the phasor diagrams and the harmonic content) of the effects of different faulty scenarios on the IM rotor cage currents represents the major contribution of this work.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 34 no. 6
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 15 June 2018

Shruti Shastri, A.K. Giri and Geetilaxmi Mohapatra

The purpose of this paper is to assess the sustainability of current accounts for five major South Asian economies, namely, India, Pakistan, Bangladesh, Sri Lanka and Nepal, for…

Abstract

Purpose

The purpose of this paper is to assess the sustainability of current accounts for five major South Asian economies, namely, India, Pakistan, Bangladesh, Sri Lanka and Nepal, for the period 1985–2016.

Design/methodology/approach

The study employs the intertemporal solvency model of Hakkio and Rush (1991) and Husted (1992). Autoregressive Distributed Lag bounds test, Gregory and Hansen’s test and Carrion-i-Silvestre and Sanso’s test are used to assess the cointegration between current account inflows and outflows. The coefficients of long-run relationship are obtained using dynamic ordinary least squares. Besides the econometric investigation, the study also examines some other indicators such as the composition of current account, size of external debt, etc., to shed further light on the sustainability of current accounts.

Findings

The study finds support for the long-run relationship between the current account outflows and inflows for all the countries. The estimates of slope coefficient indicate strong sustainability in case of India, Bangladesh and Nepal, whereas weak sustainability holds for Sri Lanka and Pakistan underscoring the need for policy interventions. In a comparative perspective, the current accounts in India, Nepal and Bangladesh conform more to a sustainable behavior in terms of the size of deficits, external debt stock and compliance to the intertemporal budget constraint.

Originality/value

The study employs econometric techniques allowing for structural breaks in the assessment of current account sustainability. Besides using the intertemporal model, the study also examines factors such as composition of current accounts, size of external debts, etc., to evaluate sustainability.

Details

South Asian Journal of Business Studies, vol. 7 no. 2
Type: Research Article
ISSN: 2398-628X

Keywords

Article
Publication date: 5 September 2016

Ying Xie, Ze Wang, Xueting Shan and Yangyang Li

Thermal stress of the rotor in a squirrel cage induction motor is generated due to the temperature rise, and the structure of the rotor will be destroyed if the stress acted on…

Abstract

Purpose

Thermal stress of the rotor in a squirrel cage induction motor is generated due to the temperature rise, and the structure of the rotor will be destroyed if the stress acted on the rotor exceeds its limits, so the thermal stress is also one of the main causes led to broken bar fault. The purpose of this paper is to report the thermal stress coupled analysis for the induction motor with healthy and faulty rotor, and to find the variation tendency of the temperature and thermal stress due to broken bars, and the part most likely to break in the rotor as a result of the thermal stress load are identified.

Design/methodology/approach

The steady temperature and thermal stress of the rotor in the case of the healthy and faulty conditions are calculated by finite element method, and the 3D model of the motor used in the experiments is established and the experimental results are presented for both healthy and faulty machines.

Findings

The influence of the broken bars fault on the motor thermal profile and thermal stress can be found, and it explains why the breaking point always appears in the joint of the bars and end rings.

Originality/value

The paper presents the 3D thermal stress coupled model and performance characteristics of induction motor with broken bars. The reasonable constraint is established according to the contact of components each other, and more reasonable fracture location is selected. The results obtained by the simulation model are in a good agreement with practical situation, because the effect of skewed rotor were taken into consideration in the process of simulation.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 35 no. 5
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 1 June 2000

K. Wiak

Discusses the 27 papers in ISEF 1999 Proceedings on the subject of electromagnetisms. States the groups of papers cover such subjects within the discipline as: induction machines;…

Abstract

Discusses the 27 papers in ISEF 1999 Proceedings on the subject of electromagnetisms. States the groups of papers cover such subjects within the discipline as: induction machines; reluctance motors; PM motors; transformers and reactors; and special problems and applications. Debates all of these in great detail and itemizes each with greater in‐depth discussion of the various technical applications and areas. Concludes that the recommendations made should be adhered to.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 19 no. 2
Type: Research Article
ISSN: 0332-1649

Keywords

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