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This paper presents a case study for multi-variable and multi-modal design optimisation of a doubly fed induction generator (DFIG) based on surrogate-model optimisation algorithm. The DFIG's winding of stator and rotor are optimised to obtain higher efficiency for rewinding purposes. First, a Latin hypercube design is selected as the design of experiments to obtain sampling points. Then, the surrogate model is constructed using Kriging Model (KRG) method based on the Latin hypercube design. Finally, the particle swarm optimisation algorithm is applied in conjunction with the finite element method to achieve the machine design optimisation.

This paper discusses coil pressing through which stator windings are compressed at high pressures to enhance the slot fill factor of electrical machines. Deterioration of insulation in compressed windings is investigated by performing quasistatic explicit dynamics finite element simulations. The results obtained from the proposed method are further investigated experimentally to validate the durability of the compressed coils. It is shown that stator windings can be compressed to a certain degree without observing material failure. In order to demonstrate the thermal advantages of densely packed stator windings, both steady state thermal finite element analysis (FEA) simulations and semi-analytical methods have also been studied. A good agreement between analytical and FEA simulations is obtained. It is noted that steady state thermal finite element modeling could be used to predict effective thermal conductivity of stator windings for different slot fill factors.

Fractional slot, concentrated-winding (FSCW) machines with saliency are being researched extensively for vehicle traction motors. However, they exhibit higher torque ripple than their equivalents without saliency. This paper identifies the origin of the torque ripple and explores potential solutions for its reduction through modification of the stator slot openings. The concept is demonstrated through modification of an in-wheel motor design for high performance electric cars.

The work is focused on investigating the performance of a linear alternator for use with external combustion - free piston engine. This family of engine can be powered either from renewable sources, scavenging waste energy from other sources of heat, or bespoke combined heat and power plants. Finite element analysis optimisation techniques followed by development of a Matlab/Simulink model were used to investigate the effects of electrical machine inductance and the combined electromagnetic loading of the machine on the resulting force. Cogging force is showed to have the most effect on the resultant force fluctuation, whereas machine inductance has showed its effect at loads exceeding (76 %) of machine rating besides reshaping the resulting force profile. The model also accounts for machine loading and total efficiency variation over mechanical cycle. This enables the system designer to investigate the effect of actual machine model thrust force on the engine performance rather than assuming the electrical machine behaves as a simple damper.

With the increased electrification of aircraft, the use of motors to replace traditionally mechanical or hydraulic auxiliary systems has increased. Aerospace motor design has the rather unique characteristics of mass and torque density being extremely important, whereas cost is less so. For low maintenance, non-safety critical components, which are only used for short durations of the flight cycle, efficiency also becomes less important, whilst eliminating an external cooling circuit and gearbox can look very attractive. In order to meet a stringent mass target, this paper considers two high torque density machines suitable for low speed applications. As mass is reduced, thermal capability becomes critical and thermal simulations are presented for operational characteristics.

An induction generator has been designed for use in an open centred tidal turbine. Mechanical constraints in the turbine design enforces a large magnetic gap in the generator, which inherently limits the power factor. The large diameter of the machine means it is likely to be constructed out of a number of segments, which can each be modelled independently and approximated to either linear segments or individual rotary machines with the same pole to air gap ratio. An analytical tool to design an induction machine for this unique set of requirements is presented and compared to results from commercial software. Detailed design options are investigated using finite element analysis before a final design is presented.

In this paper the design of a linear electrical machine for use with a free-piston engine will be discussed. Three conventional permanent magnet machines are compared to a flux switching and modulated pole machine. Each of the topologies is optimised to give a specific force whilst adhering to a limit on the mass of the moving component. Using simple vector analysis, it is shown that machine power factor and efficiency are improved by optimising the machines with an objective function of minimising the MMF. Transient solver results are used to validate the static solver results and provide estimates on efficiency and operating power factor. This method of optimisation is shown to give modulated pole machines with relatively high power factors, which is a known limitation of this class of machine. The modulated pole machine topology could be the best option among all five topologies as it has high efficiency and high power factor. The flux switching machine shows some potential benefits on magnet material use ratio compared with PMs, yet it is not compliant with mass constraint.

A novel V shape magnet motor has been designed in [1] for cost reduction compared to the existing surface-mounted in-wheel motor. The essential concept of this design is to remove the steel ribs on all ends of the magnets minimising the flux leakage. However, this approach poses a significant challenge on the structural aspect of the design. FEA was used to assess its structural integrity under various operating conditions. However, during the motor assembly, unexpected issues were raised. The adhesive, assembly tools and insertion methods were reassessed and a new solution has been proposed.

The work presents a design methodology for a tubular Moving Magnet Linear Alternator for use with an External Combustion - Free Piston Engine (EC-FPE). Modelling and design of three alternative machines of 6 slots / 7 poles composed of feasible PM arrangements have been performed to react the same EC-FPE driving force. Demonstration of geometrical constraints and design methodology for the desired force is primarily presented, from which the Radial machine is found unsuitable for the application under the given design constraints. Then, performance comparison of the remaining designed machines is listed. Comparison using a weighted score system shows that the Quasi-Halbach machine has a lighter translator mass, yet the Axial machine has higher magnet utilisation as well as higher power densities.

In recent years significant improvements in the field of Modulated Pole Machines (MPMs) have been achieved, especially in electric vehicles applications. MPMs such as Transverse Flux Machines (TFMs) are known for producing high torque densities; though further research and improvements are needed to reduce the inherently high cogging torque and torque ripple. This paper will present a method of reducing these undesirable features of TFMs through simple geometric changes, such as changing the tooth span of the stator teeth. It will be shown that a combination of varying tooth spans rather than a uniform tooth span for the whole machine helps to reduce the cogging torque and torque ripple of the machine without a significant effect on the overall torque output.

OpenHydro is developing open centred submerged turbines for the extraction of energy from ocean tides. Power take off is via a surface-mounted, radial-flux, permanent-magnet generator mounted to the rim of the turbine blades. A number of full scale devices have been deployed globally, upto 2MW and 16m diameter. The aspect ratio of the machines mean that end effects are likely to be significant and hence 3D modelling is required to fully capture them. In this paper, alternative methods for modelling the existing machine design is discussed and compared. It is demonstrated that, although a full scale detailed FEA approach yields the best results, simplified FEA and even analytical approximations are best for the purpose of designing the machines.