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Article

Cristian Demian, Raphael Romary, Gilles Vogt and Valentin Costan

The axial magnetic field occurs in the end-region of large turbo-generators is known to induce hot points or voltages between laminations, that may cause insulation…

Abstract

Purpose

The axial magnetic field occurs in the end-region of large turbo-generators is known to induce hot points or voltages between laminations, that may cause insulation breakdown and thus stator faults.

Design/methodology/approach

It is important to dispose of simple methods for estimating the axial flux rapidly with regard to the operating point of the machine.

Findings

The authors provide a practical model of the axial magnetic field based on a simplified vector diagram. The parameters required to build the vector composition of the flux densities are assessed with a limited number of finite element method simulations of the whole end-region of the machine. These simulations were validated by an experimental test on a real turbo-generator. Then the axial flux density was simply estimated for various operating points.

Originality/value

The originality of the paper concerns the practical model of the axial magnetic field based on a simplified vector diagram.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 38 no. 4
Type: Research Article
ISSN: 0332-1649

Keywords

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Article

K. Akatsu and S. Wakui

To design a high power density machine, an automatic design method is proposed. Hopefully, automatic design method uses only the requirements (torque and speed) and the…

Abstract

Purpose

To design a high power density machine, an automatic design method is proposed. Hopefully, automatic design method uses only the requirements (torque and speed) and the information about sources (voltage and current).

Design/methodology/approach

To calculate the volume, a necessary flux density and an inductance are calculated by the permeance method. All mechanical parameters, stator diameter, teeth width, turn number and so on, realize the necessary flux density and an inductance, and these parameters are expressed as a function of a rotor diameter. By using both conditions of current density and copper loss, a rotor diameter which realizes the minimum volume can be obtained.

Findings

As a result of an optimum design, 50 kW SPMSM is realized only into 2[L] spaces, which copper loss is only 500[W], 1 percent of the maximum output. Moreover, 50 kW axial flux type machine is realized only into 1.3[L] spaces. Accurate comparison is possible by only optimum designs because these have the solutions of the same conditions. In a comparison result, a volume of the axial flux machine is less than that of the radial flux machine, because the radial flux type cannot utilize the large rotor diameter. Thus the axial flux type motor is suitable to the high torque machine.

Research limitations/implications

In this research, the length of the coil end and the iron loss, are ignored, because an axial length of stator is much longer than a coil end especially for the high power motor, and the iron loss estimation has not been established.

Practical implications

By using this method, it is possible to perform the automatic design. If a designer inputs only the requested torque, speed and device information, an automatic calculation will be done, and a designer can automatically get a motor structure.

Originality/value

Although some papers can calculate the mechanical parameters which realize only torque, all requirements, torque, speed and power are satisfied in this paper. In addition, an optimum point of the volume is theoretically obtained. In industrial applications, because the power range is very important, especially for electric vehicles and so on, this paper provides more compact and more powerful machines.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 25 no. 2
Type: Research Article
ISSN: 0332-1649

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Article

Ossi Niemimäki and Stefan Kurz

The purpose of this paper is to investigate the theoretical foundation of the so-called quasi 3D modelling method of axial flux machines, and the means for the simulation…

Abstract

Purpose

The purpose of this paper is to investigate the theoretical foundation of the so-called quasi 3D modelling method of axial flux machines, and the means for the simulation of the resulting models.

Design/methodology/approach

Starting from the first principles, a 3D magnetostatic problem is geometrically decomposed into a coupled system of 2D problems. Genuine 2D problems are derived by decoupling the system. The construction of the 2D simulation models is discussed, and their applicability is evaluated by comparing a finite element implementation to an existing industry-used model.

Findings

The quasi 3D method relies on the assumption of vanishing radial magnetic flux. The validity of this assumption is reflected in a residual gained from the 3D coupled system. Moreover, under a modification of the metric of the 2D models, an axial flux machine can be presented as a family of radial flux machines.

Research limitations/implications

The evaluation and interpretation of the residual has not been carried out. Furthermore, the inclusion of eddy currents has not been detailed in the present study.

Originality/value

A summary of existing modelling and simulation methods of axial flux machines is provided. As a novel result, proper mathematical context for the quasi 3D method is given and the underlying assumptions are laid out. The implementation of the 2D models is approached from a general angle, strengthening the foundation for future research.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 33 no. 4
Type: Research Article
ISSN: 0332-1649

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Article

Javad Rahmani Fard and Mohammad Ardebili

The purpose of this paper is to investigate a novel axial flux-switching motor with sandwiched permanent magnet for direct drive electric vehicles (EVs), in which the…

Abstract

Purpose

The purpose of this paper is to investigate a novel axial flux-switching motor with sandwiched permanent magnet for direct drive electric vehicles (EVs), in which the torque density is increased and the cogging torque is decreased. For reducing the back-electromotive force (EMF) harmonics and cogging torque, a twisted structure is employed. To improve the dynamic performance of the axial field flux-switching sandwiched permanent magnet (AFFSSPM) motor a space vector modulation-direct torque and flux control scheme is proposed.

Design/methodology/approach

A multi-objective optimization is performed by means of artificial neural network and non-sorting genetic algorithm II to minimize the cogging torque while preserving the average torque.

Findings

A comparative study between two proposed machines and the conventional flux-switching permanent magnet (FSPM) machine is accomplished and the static electromagnetic characteristics are analyzed. It is demonstrated that the proposed model with twisted structure has significantly improved performance over the conventional FSPM machine in back-EMF and efficiency. The proposed controller has a speed loop only and contains neither the current loop nor hysteresis control. The AFFSSPM motor exhibits excellent dynamic performance with this scheme.

Originality value

The axial flux-switching permanent-magnet machine is one of the most efficient machines but the AFFSSPM with sandwiched permanent magnet has not been specially reported to date. Thus in this paper, the authors report on optimal design of an axial flux-switching sandwiched permanent magnet machine for electric vehicles and investigate its dynamic performance.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 36 no. 4
Type: Research Article
ISSN: 0332-1649

Keywords

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Article

Javad Rahmani Fard and Mohammad Ardebili

The purpose of this paper is to propose a novel axial field flux-switching machine with sandwiched permanent magnets. It is one of the most efficient machines which is…

Abstract

Purpose

The purpose of this paper is to propose a novel axial field flux-switching machine with sandwiched permanent magnets. It is one of the most efficient machines which is appropriate for high-torque and low-speed direct-drive applications. The proposed model is equipped with an advanced phase-group concentrated-coil winding to obtain a unity displacement winding factor. Two configurations of the proposed motors with 6-stator-slot (S)/10-rotor-pole (P) and 12S/19P are investigated. These two structures are compared with optimized a conventional axial-field flux-switching permanent-magnet (CAFFSPM) machine. Unity displacement winding factor increases the back-EMF and electromagnetic torque. Moreover, the prototype 12S/19P motor is built to verify the design.

Design/methodology/approach

The torque equation is obtained and the dimensions of the two proposed motors are determined. Some specific design issues, including the stator/rotor pole sandwiching pole angle, the stator tooth angle and the rotor pole angle have been optimized to minimize the cogging torque while maintaining the high torque density by means of response surface methodology (RSM) and 3-D finite element model of the machine.

Findings

To improve the performance, especially at high torque density, low cogging torque and high level of fault-tolerant capability, the 12S/19P axial field flux-switching sandwiched permanent-magnet (AFFSSPM) motor is proposed. Based on the optimized design, a prototype of the 12S/19P AFFSSPM motor is fabricated and tested. It is found that the experimental results validate the 3-D finite element method (FEM) simulation results.

Originality/value

The AFFSSPM motor is one of the most efficient motors, but the 12S/19P AFFSSPM motor with sandwiched permanent magnet and unity displacement winding factor has not been specially reported to date. Thus, in this paper, the authors report on optimal design of a novel axial flux-switching sandwiched permanent-magnet machine for electric vehicles and fabricate a prototype of the 12S/19P AFFSSPM motor.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 37 no. 2
Type: Research Article
ISSN: 0332-1649

Keywords

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Article

Mohammadreza Baghayipour, Ahmad Darabi and Ali Dastfan

This paper aims to propose an analytical model for the harmonic content no-load magnetic fields and Back electric motive force (EMF) in double-sided TORUS-type non-slotted…

Abstract

Purpose

This paper aims to propose an analytical model for the harmonic content no-load magnetic fields and Back electric motive force (EMF) in double-sided TORUS-type non-slotted axial flux permanent magnet (TORUS-NS AFPM) machines with surface-mounted magnets considering the winding distribution and iron saturation effects.

Design/methodology/approach

First, a procedure to calculate the winding distribution with a rectangular cross-section is proposed. The magnetic field distribution and magnetic motive force (MMF) drop due to saturation in iron cores are then exactly extracted in a 2-D analytical model. The consequent influence on air-gap magnetic field and Back EMF are also calculated using a new iterative algorithm. The results are compared with those of the conventional analytical model without saturation, 2-D finite element analysis (FEA) and an experiment on a fabricated prototype machine.

Findings

Unlike the conventional method, the new method yields the no-load magnetic field distributions in air-gap and iron cores and Back EMF very exactly such that the results well match to those of the FEA and experiment.

Originality/value

Unlike the conventional winding factor, the winding distribution is considered here along the both axial and circumferential directions, which improves the accuracy level of results for non-slotted structures with relatively large air-gaps. The magnetic field distribution and MMF drop-in iron parts are also calculated as the basis for exact recalculation of air-gap magnetic field and Back EMF. Because of small computational burden beside superior accuracy, the proposed model can be treated as an accurate and fast substitute for FEA to be used during the design procedure or for predicting the other performance characteristics of TORUS-NS AFPM machines.

Details

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

Keywords

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Article

Javad Rahmani Fard and Mohammad Ardebili

The purpose of this paper is to suggest a novel current sensor-less drive system for a novel axial flux-switching permanent-magnet motor drive to reduce the costs and…

Abstract

Purpose

The purpose of this paper is to suggest a novel current sensor-less drive system for a novel axial flux-switching permanent-magnet motor drive to reduce the costs and avoid problems caused by faults of the current sensors.

Design/methodology/approach

Commonly, a conventional controller needs at least two current sensors; in this paper, the current sensors are removed by replacing estimated stator current with the extended Kalman filter.

Findings

A prototype of the novel axial flux-switching permanent-magnet motor is fabricated and tested. It is found that the experimental results confirm the proposed method and show that the control has almost the same performance and ability as the conventional control.

Originality/value

The axial flux-switching permanent-magnet motor is one of the most efficient motors, but current sensor-less control of an axial flux-switching permanent-magnet motor with a sandwiched permanent magnet and a unity displacement winding factor has not been specially reported to date. Thus, in this paper, the authors report on current sensor-less control based on the extended Kalman filter for electric vehicles.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 37 no. 6
Type: Research Article
ISSN: 0332-1649

Keywords

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Article

Qinfen Lu, Yihua Yao and Yunyue Ye

The purpose of this paper is propose a novel integrative transverse-flux linear compressor (TFLC), which integrates compressor into a single-phase transverse-flux linear…

Abstract

Purpose

The purpose of this paper is propose a novel integrative transverse-flux linear compressor (TFLC), which integrates compressor into a single-phase transverse-flux linear oscillating actuator with moving magnet. Its main merit is having similar lamination as rotate motor which is easy to be stacked.

Design/methodology/approach

The simple lumped circuit model accounting for magnetic saturation, armature reaction and axial fringing effect is proposed. Based on this model, the magnetic field in air gap is calculated, and then the optimal PM height, PM length, split ratio and pole number are found. The predicted thrust force, stroke and system resonant frequency at no load are validated by prototype measurement. The relation of system resonant frequency and load are also measured.

Findings

In this novel TFLC, the optimal split ratio is in area of 0.54∼0.56 and pole number is 6. For designed stroke 10 mm, suitable PM height and length are 3 mm and 63 mm, respectively. By measurement, the predicted thrust force, stroke and system resonant frequency at no load are validated. The measurement also shows that the system resonant frequency can be improved from 30 Hz of no load to 39 Hz at 0.7 Mpa air load.

Originality/value

The novel TFLC has excellent driving performance and simple structure for maintenance. It can produce enough pressure to meet the requirement of refrigerator, so it is a strong candidate for refrigerating apparatus.

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

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Article

Naghi Rostami and Majid Rostami

The purpose of this paper is the fast and accurate modelling of surface-mounted Axial-Flux Permanent-Magnet (AFPM) machines equipped with cylindrical magnets using…

Abstract

Purpose

The purpose of this paper is the fast and accurate modelling of surface-mounted Axial-Flux Permanent-Magnet (AFPM) machines equipped with cylindrical magnets using quasi-3D approach. Furthermore, the accuracy of the method is improved by using leakage coefficient, saturation coefficient and an appropriate permeance function.

Design/methodology/approach

Quasi-3D approach is used for fast and accurate modelling of AFPM machines. Air-gap flux density distribution, induced back EMF, and produced cogging torque are calculated using the proposed method with reasonable accuracy.

Findings

The results obtained by quasi-3D approach compared to Finite-Element-Analyses (FEA) shows how accurate, fast and efficient this method is. It is proved that, this method can be successfully applied to evaluate the performance of the AFPM machines.

Originality/value

Effectiveness and accuracy of quasi-3D approach is assessed on different AFPM machines. Furthermore, to increase the accuracy of computations, the effects of the magnetic potential drop at iron parts of the machine are taken into account by using a saturation coefficient. Besides, the influence of the slot opening on the flux density distribution is taken into account by using an appropriate relative permeance function.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 36 no. 4
Type: Research Article
ISSN: 0332-1649

Keywords

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Article

Huang Jun, Q.W. Wang and W.Q. Tao

A computational study of convective heat transfer for turbulent flows in multi‐channel, narrow‐gap fuel element has been carried out, using a general marching procedure…

Abstract

A computational study of convective heat transfer for turbulent flows in multi‐channel, narrow‐gap fuel element has been carried out, using a general marching procedure. The fluid distribution adjustment among seven annular‐sector channels is based on the assumption of the same pressure drop in these passages. It was found that the inlet velocities of the bilateral channels are lower than those of the middles, and the axial local heat transfer coefficients for the seven channels do not approach the fully developed constant value. At each cross section, the periphery temperature distribution is not uniform, while the local temperature distribution along axial coordinate is of sinuous type with the peak at x=0.7–0.8 m. At the same Reynolds number, the averaged Nusselt numbers of water in Channel 1 and Channel 7 are higher than those in the middles. The maximum surface temperature increases almost linearly with the inlet water temperature, whereas it decreases almost asymptotically with the inlet average velocity.

Details

Engineering Computations, vol. 19 no. 3
Type: Research Article
ISSN: 0264-4401

Keywords

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