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Article
Publication date: 1 June 1944

H. Rissik

A FREQUENTLY recurring problem, more particularly in the sphere of electrical engineering practice, is the determination of the equivalent rating of a machine or piece of…

Abstract

A FREQUENTLY recurring problem, more particularly in the sphere of electrical engineering practice, is the determination of the equivalent rating of a machine or piece of apparatus under conditions of intermittent loading. By equivalent rating is to be understood the value of the continuous load, whether expressed in terms of current or power, which will produce the same final temperature rise as is actually produced by the given intermittent load.

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Aircraft Engineering and Aerospace Technology, vol. 16 no. 6
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 8 March 2021

Rohollah Abdollahi

The purpose of this paper is to provide a T autotransformer based 12-pulse rectifier with passive harmonic reduction in more electric aircraft applications. The T…

Abstract

Purpose

The purpose of this paper is to provide a T autotransformer based 12-pulse rectifier with passive harmonic reduction in more electric aircraft applications. The T autotransformer uses only two main windings which result in volume, space, size, weight and cost savings. Also, the proposed unconventional inter-phase transformer (UIPT) with a lower kVA rating (about 2.6% of the load power) compared to the conventional inter-phase transformer results in a more harmonic reduction.

Design/methodology/approach

To increase rating and reduce the cost and complexity of a multi-pulse rectifier, it is well known that the pulse number must be increased. In some practical cases, a 12-pulse rectifier (12PR) is suggested as a good solution considering its simple structure and low weight. But the 12PR cannot technically meet the standards of harmonic distortion requirements for some industrial applications, and therefore, they must be used with output filters. In this paper, a 12PR is suggested, which consists of a T autotransformer 12PR and a passive harmonic reduction (PHR) based on the UIPT at direct current (DC) link.

Findings

To show the advantage of this new combination over other solutions, simulation results are used, and then, a prototype is implemented to evaluate and verify the simulation results. The simulation and experimental test results show that the input current total harmonic distortion (THD) of the suggested 12PR with a PHR based on UIPT is less than 5%, which meets the IEEE 519 requirements. Also, it is shown that in comparison with other solutions, it is cost effective, and at the same time, its power factor is near unity, and its rating is 29.92% of the load rating. Therefore, it is obvious that the proposed rectifier is a practical solution for more electric aircrafts.

Originality/value

The contributions of this paper are summarized as follows. The suggested design uses a retrofit T autotransformer, which meets all technical constraints, and in comparison, with other options, has less rating, weight, volume and cost. In the suggested rectifier, a PHR based on UIPT at its dc link of 12PR is used, which has good technical capabilities and lower ratings. In the PHR based on UIPT, an IPT is used, which has an additional secondary winding and four diodes. This solution leads to a reduction in input current THD and conduction losses of diodes. In full load conditions, the input line current THD and power factor are 4% and 0.99, respectively. The THD is less than 5%, which satisfies IEEE-519 and DO-160G requirements.

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Circuit World, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0305-6120

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Article
Publication date: 1 May 1972

IN a departure from usual practice this issue concentrates to a large extent upon a single subject — Mechanical Handling. It coincides with that industry's exhibition at…

Abstract

IN a departure from usual practice this issue concentrates to a large extent upon a single subject — Mechanical Handling. It coincides with that industry's exhibition at Earls Court from the 9th to 19th of this month, to be opened by the Rt. Hon. Christopher Chataway, M.P., Minister for Industrial Development. In consequence it was necessary to defer some regular features for a time, for which we apologise.

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Work Study, vol. 21 no. 5
Type: Research Article
ISSN: 0043-8022

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Article
Publication date: 1 February 1989

Bennett J. Price

Uninterruptible Power Supply (UPS) systems are typically designed to provide power to computers for five to thirty minutes after all utility company power has failed. In…

Abstract

Uninterruptible Power Supply (UPS) systems are typically designed to provide power to computers for five to thirty minutes after all utility company power has failed. In addition to providing blackout and brownout protection, many UPS systems also protect against spikes, surges, sags, and noise, and some also offer many of the features found in power distribution units (PDUs). The major components or subsystems of a typical UPS system are detailed, and a sample bid specification is appended. Three sidebars discuss UPSs and air conditioning, the maintenance bypass switch (MBS), and literature for further reading.

Details

Library Hi Tech, vol. 7 no. 2
Type: Research Article
ISSN: 0737-8831

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Article
Publication date: 2 January 2018

Ashish Kumar Sinha, Sukanta Das and Tarun Kumar Chatterjee

Condition monitoring of squirrel cage induction motors (SCIMs) is indispensible for achieving fault-free working environment. As broken rotor bars (BRBs) are one of the…

Abstract

Purpose

Condition monitoring of squirrel cage induction motors (SCIMs) is indispensible for achieving fault-free working environment. As broken rotor bars (BRBs) are one of the more frequent faults in a SCIM especially where direct-on-line starting is indispensible, as in underground mines, a priori knowledge of fault severity in terms of the number of BRBs assists in effective fault monitoring. In this regard, this paper aims to propose a unique empirical relation to facilitate the determination of number of BRB.

Design/methodology/approach

Fast Fourier transform is used to obtain fault sideband amplitudes under varying number of BRBs and load torque for 5.5 kW, 7.5 kW, 10 kW, three-phase, 415 V, 50 Hz SCIMs in MATLAB/Simulink. The nature of variation is decided by an appropriate curve fitting technique for comprehending a unique empirical relation. The proposed empirical relation is validated by bootstrapping and z-test. Furthermore, hardware validation is done using 1 kW laboratory prototype with Labview interface.

Findings

The analytical study reveals the dependence of lower and upper sideband amplitudes on the number of BRBs, load torque and machine rating. Therefore, fault severity in terms of number of BRBs is accurately calculated using the proposed empirical relation if load torque, machine rating and amplitudes of lower and upper sidebands are known.

Originality/value

The unique empirical relation proposed in the present work provides accurate knowledge of fault severity in terms of the number of BRBs. This facilitates maintenance scheduling which shall reduce effective downtime and improve production.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 37 no. 1
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 2 January 2018

Mahmoud M. Elkholy

The paper aims to present an application of teaching learning-based optimization (TLBO) algorithm and static Var compensator (SVC) to improve the steady state and dynamic…

Abstract

Purpose

The paper aims to present an application of teaching learning-based optimization (TLBO) algorithm and static Var compensator (SVC) to improve the steady state and dynamic performance of self-excited induction generators (SEIG).

Design/methodology/approach

The TLBO algorithm is applied to generate the optimal capacitance to maintain rated voltage with different types of prime mover. For a constant speed prime mover, the TLBO algorithm attains the optimal capacitance to have rated load voltage at different loading conditions. In the case of variable speed prime mover, the TLBO methodology is used to obtain the optimal capacitance and prime mover speed to have rated load voltage and frequency. The SVC of fixed capacitor and controlled reactor is used to have a fine tune in capacitance value and control the reactive power. The parameters of SVC are obtained using the TLBO algorithm.

Findings

The whole system of three-phase induction generator and SVC are established under MatLab/Simulink environment. The performance of the SEIG is demonstrated on two different ratings (i.e. 7.5 kW and 1.5 kW) using the TLBO algorithm and SVC. An experimental setup is built-up using a 1.5 kW three-phase induction machine to confirm the theoretical analysis. The TLBO results are matched with other meta heuristic optimization techniques.

Originality/value

The paper presents an application of the meta-heuristic algorithms and SVC to analysis the steady state and dynamic performance of SEIG with optimal performance.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 37 no. 1
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 1 December 2000

Osama A. Jannadi and Hamed Al‐Saggaf

Quality problems in the service organization are the result of the mismatch between prior expectation and perceived quality of the service. Each organization will attempt…

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Abstract

Quality problems in the service organization are the result of the mismatch between prior expectation and perceived quality of the service. Each organization will attempt to determine the requirements of its customers and translate these requirements into product and delivery process specifications. This paper examines a particular electric company (SCECO‐East), a typical service provider in Saudi Arabia, in which service quality is a distinguishing feature of primary importance. It describes a detailed survey and analysis in the light of the model put forward by Parasuraman et al. It utilizes SERVQUAL for measuring customers’ perceptions of service quality. The study revealed that SCECO‐East scored high in tangibles dimension but low in features of responsiveness and reliability. In addition, while the performance of SCECO‐East was acceptable to all customer categories, service quality was perceived differently by various types of customers, with reinforcement and commercial customers awarding SCECO‐East even lower ratings than other customers did.

Details

International Journal of Quality & Reliability Management, vol. 17 no. 9
Type: Research Article
ISSN: 0265-671X

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Article
Publication date: 3 December 2018

Kanwal Jit Singh, Inderpreet Singh Ahuja and Jatinder Kapoor

This review paper reveals the literature on ultrasonic, chemical-assisted ultrasonic and rotary ultrasonic machining (USM) of glass material. The purpose of this review…

Abstract

Purpose

This review paper reveals the literature on ultrasonic, chemical-assisted ultrasonic and rotary ultrasonic machining (USM) of glass material. The purpose of this review paper is to understand and describe the working principle, mechanism of material removal, experimental investigation, applications and influence of input parameters on machining characteristics. The literature reveals that the ultrasonic machines have been generally preferred for the glass and brittle work materials. Some other non-traditional machining processes may thermally damage the work surface. Through these USM, neither thermal effects nor residual stresses have been generated on the machined surface.

Design/methodology/approach

Various input parameters have the significant role in machine performance characteristics. For the optimization of output response, several input parameters have been critically investigated by the various researcher.

Findings

Some advance types of glasses such as polycarbonate bulletproof glass, acrylic heat-resistant glass and glass-clad polycarbonate bulletproof glass still need some further investigation because these materials have vast applications in automobile, aerospace and space industries.

Originality/value

Review paper will be beneficial for industrial application and the various young researcher. Paper reveals the detail literature review on traditional ultrasonic, chemical assisted ultrasonic and rotary USM of glass and glass composite materials.

Details

World Journal of Engineering, vol. 15 no. 6
Type: Research Article
ISSN: 1708-5284

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Book part
Publication date: 20 June 2017

David Shinar

Abstract

Details

Traffic Safety and Human Behavior
Type: Book
ISBN: 978-1-78635-222-4

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Article
Publication date: 14 July 2021

Irindu Upasiri, Chaminda Konthesingha, Anura Nanayakkara, Keerthan Poologanathan, Brabha Nagaratnam and Gatheeshgar Perampalam

In this study, the insulation fire ratings of lightweight foamed concrete, autoclaved aerated concrete and lightweight aggregate concrete were investigated using finite…

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Abstract

Purpose

In this study, the insulation fire ratings of lightweight foamed concrete, autoclaved aerated concrete and lightweight aggregate concrete were investigated using finite element modelling.

Design/methodology/approach

Lightweight aggregate concrete containing various aggregate types, i.e. expanded slag, pumice, expanded clay and expanded shale were studied under standard fire and hydro–carbon fire situations using validated finite element models. Results were used to derive empirical equations for determining the insulation fire ratings of lightweight concrete wall panels.

Findings

It was observed that autoclaved aerated concrete and foamed lightweight concrete have better insulation fire ratings compared with lightweight aggregate concrete. Depending on the insulation fire rating requirement of 15%–30% of material saving could be achieved when lightweight aggregate concrete wall panels are replaced with the autoclaved aerated or foamed concrete wall panels. Lightweight aggregate concrete fire performance depends on the type of lightweight aggregate. Lightweight concrete with pumice aggregate showed better fire performance among the normal lightweight aggregate concretes. Material saving of 9%–14% could be obtained when pumice aggregate is used as the lightweight aggregate material. Hydrocarbon fire has shown aggressive effect during the first two hours of fire exposure; hence, wall panels with lesser thickness were adversely affected.

Originality/value

Finding of this study could be used to determine the optimum lightweight concrete wall type and the optimum thickness requirement of the wall panels for a required application.

Details

Journal of Structural Fire Engineering, vol. 12 no. 3
Type: Research Article
ISSN: 2040-2317

Keywords

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