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This paper aims to study the relationship between leakage flux coefficient and the coreless axial magnetic field permanent magnet synchronous generator (AFPMSG) size and obtain the expressions of leakage flux coefficient.

In this paper, a magnetic circuit model of coreless AFPMSG is proposed. Four kinds of leakage permeances of permanent magnet (PM) are considered, and the expression of no-load leakage flux coefficient is obtained. Solving the integral region of leakage permeances by generator size, which improves the accuracy of the solution.

Finite element method and magnetic circuit method are used to obtain the no-load leakage flux coefficient and its variation trend charts with the change of pole arc coefficient, air gap length and PM thickness. The average errors of the two methods are 2.835%, 0.84% and 1.347%, respectively. At the same time, the results of single-phase electromotive force obtained by magnetic circuit method, three dimensional finite element method and prototype experiments are 19.36 V, 18.82 V and 19.09 V, respectively. The results show that the magnetic circuit method is correct in calculating the no-load leakage flux coefficient.

The special structure of the coreless AFPMSG is considered in the presented equivalent magnetic circuit and equations, and the equations in this paper can be applied for leakage flux evaluating purposes and initial parameter selection of the coreless AFPMSG.

Design of small disc-type permanent magnet (PM) brushed DC motors for servomechanisms is challenging. The purpose of this paper is to propose a special coreless double-sided structure. This easy to manufacture motor has two set of shifted concentrated windings on both sides of the rotor. All of the coils in each winding are simply connected in series. A simple arcless commutator, which shares the features of both the usual commutators and slip rings, is connected to each winding at only two points.

By replacing the PMs with an equivalent current density, main design equations of the motor have been derived through the solving of scalar Poisson equation. A radial division technique has been used to take the radial variations into account. This provides the ability of considering various shapes of coils and PMs. A novel iterative algorithm has been proposed to design a motor with high torque capability, compared to other coreless counterparts. Some design variables are obtained based on an independent optimization problem, which maximizes the active portion of windings. The other variables are calculated in such a way that the design requirements are satisfied.

The feasibility and capability of the new structure have been proved by prototyping a sample motor. Comparing the design outputs with the results of the 3D finite element analysis and experimental tests shows a good agreement. This verifies the accuracy of the proposed design method.

A new structure for PM brushed DC motors and a novel algorithm for its design has been developed.

This article seeks to present the simple and easy to manufacture design of a permanent magnet generator based on coreless windings. An example is shown of basic calculations based on an equivalent magnetic circuit. Finally, a description of a 20 kW prototype of PMSG is presented based on rectangular magnets which contains mechanical design and experimental results.

The analysis presents flux dependence using several parameters such as: magnet's grade and size in comparison with coil and air‐gap dimensions. The second part of the article concentrates on simulation results of Finite Element Method analysis (FEM) that clearly shows the flux distribution for different magnet shapes – trapezoidal and rectangular.

The presented topology of the machine has several advantages, e.g. there is no starting and cogging torque which is very important especially for wind power systems because of the start up point of the turbine. Moreover, it is cheap and easy to manufacture because of ironless technology in stator. The generator can be produced in the range of single watts up to hundreds of kilo watts of power in multi disk operation.

The ironless technology applied to the stator, results in the need for using stronger magnets in comparison with a classic iron‐core permanent magnet machine.

This axial‐flux machine seems to be very interesting for low speed power generation systems such as wind and water turbines. Cost effective permanent magnet generator can be used for local power generation (e.g. heating). The generator can also be connected to the main grid through a special grid‐tie‐inverter.

The article presents the simple and rarely presented topology and describes a few methods of optimisation of the parameters to achieve maximum power.

The purpose of this paper is to compare the methods of calculating the parameters of air-cored stator flux permanent magnet generator and to compare these results with the measurements of the designed and manufactured generator. The generator is to be designed for operation in a wind power plant.

An analytical method and 2D and 3D finite element methods (FEMs) were used to calculate the parameters of the coreless permanent magnet axial generator. The analytical method and 2D FEM were applied to individual cross-sections through the air gap of the machine. After the design and construction of the generator and measuring station, the results of calculations and measurements were compared.

The results of investigated calculation methods and measurements were found to be mutually compatible. Analytical methods and 2D FEM required proper interpretation of the results when comparing them with the 3D FEM. The results of the measurements and calculations showed the usefulness of the generator for operation in a wind power plant.

Full comparison of results of 2D and 3D calculations with the results of the measurements on the machine model confirmed the usefulness of fast 2D methods for the analysis of coreless generators. The results differed by the effects of leakage inductance of windings’ front connections. The application of an axial generator designed with the described methods in a wind turbine showed its proper operation.

Recent advances in nano and picosatellite missions and future such missions require faster and accurate pointing accuracies using reaction wheels for attitude control purposes. The ability to put one or three reaction wheels on the spacecraft in the 1‐20 kg range enables new classes of missions. The purpose of this paper is to present the detailed design, analysis, and construction of a miniature reaction wheel prototype. The designed pico‐reaction wheel promises to fulfill the need for low cost, low mass, low power, high reliability, and high‐accuracy attitude control systems for applications such as communications, remote sensing, and space science.

Details about the design, analysis and development of pico‐reaction wheel are discussed. The development status of the system is outlined and the working prototype of the device is described and some preliminary test results are given. Requirements specifications, design and analysis and finite element analysis are covered.

A fully functional prototype has been developed and testing has been conducted that demonstrated the effectiveness of the device. The pico‐reaction wheel offers a new attitude control system implementation strategy for pico and nanosatellite missions that can help to significantly reduce the spacecraft costs. The key to our success has been to design the reaction wheel from ground‐up for simplicity.

The designed pico‐reaction wheel satisfied all the constraints and requirements. Furthermore, its advantages include scalability and modularity by virtue of using commercial‐off‐the‐shelf components. A pico‐reaction wheel has been successfully designed and is now available to pico and nanosatellite builders at a cost that is consistent with low‐cost research missions.

Consideration of leakage fluxes in the preliminary design stage of a machine is important for accurate determination of machine dimensions and prediction of performance characteristics. This paper aims to obtain some equations for calculating the average air gap flux density, the flux density within the magnet and the air gap leakage flux factor.

A detailed magnetic equivalent circuit (MEC) is presented for a TORUS-type non-slotted axial flux permanent magnet (TORUS-NS AFPM) machine. In this MEC, the leakage flux occurring between two adjacent magnets and the leakage fluxes taking place between the magnet and rotor iron at the interpolar, inner and outer edges of the magnets are considered. According to the proposed MEC and by using flux division law, some equations are extracted. A three-dimensional finite element method (FEM) is used to evaluate the proposed analytical equations. The study machine is a 3.7 kW and 1,400 rpm TORUS-NS AFPM machine.

The air gap leakage flux factor, the average air gap flux density and the flux density within the magnet are calculated using the proposed equations and FEM. All the results of FEM confirm the excellent accuracy of the proposed analytical method.

The new equations presented in this paper can be applied for leakage flux evaluating purposes.

Optimisation in electromagnetics, based on finite element models, is often very time‐consuming. In this paper, we present the space‐mapping (SM) technique which aims at speeding up such procedures by exploiting auxiliary models that are less accurate but much cheaper to compute.

The key element in this technique is the SM function. Its purpose is to relate the two models. The SM function, combined with the low accuracy model, makes a surrogate model that can be optimised more efficiently.

By two examples we show that the SM technique is effective. Further we show how the choice of the low accuracy model can influence the acceleration process. On one hand, taking into account more essential features of the problem helps speeding up the whole procedure. On the other hand, extremely simple auxiliary models can already yield a significant acceleration.

Obtaining the low accuracy model is not always straightforward. Some research could be done in this direction. The SM technique can also be applied iteratively, i.e. the auxiliary model is optimised aided by a coarser one. Thus, the generation of hierarchies of models seems to be a promising venue for the SM technique.

Optimisation in electromagnetics, based on finite element models, is often very time‐consuming. The results given show that the SM technique is effective for speeding up such procedures.

PRODUCTIVITY is a constant awareness of the need to make more efficient use of the production resources, and the efficiency/performance returns in each factory will testify to the thoroughness of work study. There will be those factories where work study is discredited in that production methods have remained static, original study work has not been properly recorded and amendments have gone by the board with the inevitable consequence that standards slip. Any work study findings are no longer accepted as valid with the result that work measurement degenerates to the level of rate fixing.