Thermal and Electromagnetic Stator Vent Design Optimisation for Synchronous Generators

© 2020 Institute of Electrical and Electronics Engineers Inc.. All rights reserved. This paper deals with the stator cooling of an air-cooled, synchronous generator with a power rating of 400 kVA, which has been improved by adding two radial vents to the stator. To ensure an optimal vent design, a novel combined thermal and electromagnetic modelling approach is developed. A parametric 3D Conjugate Heat Transfer Computational Fluid Dynamics (CFD) model is used for the thermal modelling. An electromagnetic 2D Finite Element Analysis determined the impact that venting the stator has on the loss distribution. The models are coupled by deriving analytical correlations between the combined vent width and rotor copper, rotor iron and stator iron losses. These correlations are implemented into the optimisation procedure of the parametric CFD model. Five design parameters are optimised simultaneously with the aim of minimising the peak stator winding temperature. The modelling approach was validated experimentally by thermal, torque and mass flow measurements on the benchmark machine, as well as the newly designed prototype

Development of a scaled doubly-fed induction generator for assessment of wind power integration issues

Years of experience have been dedicated to the advancement of thermal power plant technology, and in the last decade the investigation has focused on the wind energy conversion system (WECS). Wind energy will play an important role in the future of the energy market, due to the changing climate and the fossil fuel crisis. Initially, wind energy was intended to cover a small portion of the energy market, but in the long term it should compete with conventional fossil fuel power generation. The movement of the power system towards this new phenomena has to be investigated before the wind energy share increases in the network. Therefore, the wind energy integration issues serve as an interesting topic for authors to improve the perception of integration, distribution, variability and power flow issues. Several simulation models have been introduced in order to resolve this issue, however, the variety in types of wind turbines and the network policies result in these models having limited accuracy or being developed for specific issues. The micro-machine is introduced in order to overcome the challenges of simulation models and the costs involved in field tests. In the past, the grid integration issue of large turbo-alternators was solved by the micro-machines. A variety of tests are possible with the micro-machines and they also increase the flexibility of the system. The increased accuracy as well as the ability to carry out real-time analysis and compare actual field test data are strengths worth utilizing. This project involves the designing and the prototyping of a scaled doubly-fed induction generator (micro-DFIG). The machine is also analysed and tested. The scaling of the micro-machine is achieved by means of a dimensional analysis, which is a mathematical method that allows machines and systems to be downscaled by establishing laws of similitude between the reference model and its scaled model. MATLAB/SIMULINK, Maxwell and Solid Work are employed to achieve the objectives of this project

Dimensioning Optimization of the Permanent Magnet Synchronous Generator for Direct Drive Wind Turbines

In the present work, a methodology that allows optimizing the permanent magnet synchronous generator (PMSG) design by establishing limit values of magnet radius and length that maximize efficiency for the nominal parameters of the wind turbine is developed. The methodology consists of two fundamental models. One model calculates the generator parameters from the radius of the magnet base, and the other optimization model determines two optimum generators according to the optimization criteria of maximum efficiency and maximum efficiency with minimum weight starting from the axial length and the radius of the magnet base. For the optimization, the numerical method of the golden section was used. The model was validated from a 10 kW PMSG and the results of two optimum generators are presented according to the optimization criteria. In addition, when the obtained results are compared with the reference electric generator, an increase in efficiency of 1.15% and 0.81% and a reduction in weight of 30.79% and 39.15% of the optimized generators are obtained for maximum efficiency and minimum weight, respectively. Intermediate options between the maximum efficiency generator and the minimum weight generator allows for the selection of the optimum dimensioning for the electric generator as a function of the parameters from the wind turbine design

Improved damper cage design for salient-pole synchronous generators

The benefits of implementing a damper winding in salient-pole, synchronous generators are widely known and well consolidated. It is also well known that such a winding incurs extra losses in the machine due to a number of reasons. In order to improve the overall efficiency and performance of classical salient-pole, wound field, synchronous generators that employ the traditional damper cage, an improved amortisseur winding topology that reduces the inherent loss is proposed and investigated in this paper. This is essential in order to meet modern power quality requirements and to improve the overall performance of such ’classical’ machines. The new topology addresses the requirements for lower loss components without compromising the acceptable values of the output voltage total harmonic distortion and achieves this by having a modulated damper bar pitch. As vessel for studying the proposed concept, a 4MVA, salient-pole, synchronous generator is considered. A finite element model of this machine is first built and then validated against experimental results. The validated model is then used to investigate the proposed concept with an optimal solution being achieved via the implementation of a genetic algorithm optimization tool. Finally, the performance of the optimised machine is compared to the original design both at steady state and transient operating conditions

AI-based hybrid optimisation of multi-megawatt scale permanent magnet synchronous generators for offshore wind energy capture

The finite nature of earth’s natural resources has become a post-industrial reality. Despite their alarming depletion, fossil fuels still dominated the global final energy landscape. Technological advances and rapid deployment of various renewable energy technologies have demonstrated their potential at reducing the worlds dependency on fossil fuels and their negative impacts. Presently, wind energy is the most cost-effective means of renewable energy conversion in the developed world and has currently has a price point that is in direct competition with fossil fuel. Coupled with the low price, the adoption of wind power has seen capacity increases in excess of 650% over the last ten years. Permanent Magnet Synchronous Generators (PMSGs) have become prominent in large wind energy system applications. The Radial Flux machine topology has become particularly attractive. In order to improve the competitiveness of large wind energy systems, the main focal point of current research is toward reducing the Levelised Cost of Energy (LCOE) of the systems. A proven method of reducing the LCOE of wind power generation is by upscaling RF-PMSGs to the multi mega-watt (MW) range. For the much wider adoption of wind power generation, the cost of energy (price/MWh) needs to be driven down further, by the development of more efficient and cost-effective ways to harvest the vast amounts of energy. The main objective of this dissertation is the drive-train selection, detailed design, sizing and optimisation of a 10.8 MW permanent magnet radial flux synchronous generator (RF-PMSG) to be used in the next generation of offshore wind farms. From an analytical viewpoint, the results suggested the use of a medium speed RF-PMSG utilizing a single-stage geared drivetrain, together with a MV voltage rating (3.3kV) for the 10.8 MW RF-PMSG designed in the thesis. Finally, this dissertation proposes a promising hybrid, analytical-numerical optimisation of a 10.8 MW RF-PMSG to be used for offshore Wind Energy Conversion. The hybrid optimisation utilises a two-stage optimisation strategy that incorporates both an analytical and a numerical (FEA) optimisation; using the DE algorithm and the Taguchi method respectively. Although the permanent magnet losses are neglected in the analytical loss calculations, they are included in the numerical FE portion of the hybrid optimisation. The initial stage (STAGE I) of the hybrid optimisation utilised the DE algorithm. The objective function was set to reduce the initial cost (!"#""*+) in the generator, i.e. NdFeB PM mass (',-), copper mass (').), and active steel in the stator lamination and rotor core ('/0++&), while maintaining a pmsg efficiency (23456 ≥ 97%). The initial stage saw a reduction in initial cost by 25.5%, while maintaining an efficiency of 23456 = 97.8%. The final stage (STAGE II) of the hybrid optimisation utilising the Taguchi method, to make improvements on the performance of the machine, by optimising the Torque and back EMF characteristics while further reducing the NdFeB PM mass. The Magnet Fill Factor (APM), the Slot opening (bs0), the thickness of the permanent magnet poles (ℎ34) and the equivalent length of the air gap (?6) were used as optimisation variables. The final stage saw a decrease in cogging torque (@)06) by 53.4%, an increase in average torque (@%*) by 1.1%, a reduction in the total harmonic distortion of the back EMF (@AB) by 8.0%, a reduction in the required mass of the NdFeB permanent magnet material by 12.43%, while maintaining a torque ripple (@C"3) < 10%. The RF-PMSG characteristics optimised using the hybrid analytical-numerical optimisation were hypothesised to contribute in a reduction of the LCOE of offshore wind energy both in terms of Operational expenditure (OPEX) and Capital expenditure (CAPEX)

Design and Modelling Linear Motor for Air Conditioning Compressor System

The increasing in temperature on the surrounding had increased the demand on the air conditioning usage. As air conditioning usage increase, the power consumption on the usage of air conditioning is also increase hence the energy demand increase. In addition, the type of air conditioning system also developed from conventional air conditioning to hybrid inverter air conditioning in order to minimize the usage of power consumption. However, the power consumption of air conditioning still high due to less efficiency of air conditioning compressor system. This phenomenon has driven the search of an alternative way to decrease the power consumption inside the air conditioning. This research main focus on the air conditioning compressor system where many technologies are available for air conditioning however the efficiency of the air conditioning compressor system is low. Thus, a linear motor is designed for this project, the research focuses on the air conditioning linear motor application instead of the current technology which is rotary motor for the air conditioning compressor system

Studies in Electrical Machines & Wind Turbines associated with developing Reliable Power Generation

The publications listed in date order in this document are offered for the Degree of Doctor of Science in Durham University and have been selected from the author’s full publication list. The papers in this thesis constitute a continuum of original work in fundamental and applied electrical science, spanning 30 years, deployed on real industrial problems, making a significant contribution to conventional and renewable energy power generation. This is the basis of a claim of high distinction, constituting an original and substantial contribution to engineering science

A hollow-shaft rotor cooling system for automotive traction motors

PhD ThesisAutomotive traction motors with demanding power density requirements, are exposed to higher temperature operations, which can have a detrimental effect on the efficiency, reliability and life expectancy of these motors. In order to minimize this level of damaging, a highly effective cooling and ventilating system has to be incorporated into the optimal design of such motors. It can ensure sufficient heat removal from the machine inside. On top of this, a better cooling performance of the rotor will result in higher power density, better field weakening capability and reduced costs. This thesis addresses a hollow-shaft rotor cooling system for automotive traction motors. In such cooling system, the coolant is forced to pass through a hollow-shaft in order to cool the motor. However, in such case, the heat transfer can be complex due to the secondary flow which will occur as a result of the shaft rotation. As a result, the convective heat transfer coefficient (HTC) correlation of a stationary case is invalid for a hollow-shaft rotor cooling system. The aim of this thesis is to investigate the effects of the rotational velocities, coolant flow rates and coolant temperature, on the thermal performance of this cooling method. A simplified numerical model based on computational fluid dynamics (CFD) methods was developed to provide a qualitative understanding of the mechanism of convective heat transfer. Then a finite element model (FEM) was constructed to represent the heat transfer of the test rig by considering heat dissipation of conduction and convection. Experiments were then carried out to validate the accuracy of CFD models with the assistance of an analytical lumped-parameter thermal network (LPTN) approach. As a result of such analysis, two new dimensionless correlations of the Nusselt number with the Reynolds number are derived for turbulent and laminar flow, respectively. These correlations can be applied in different geometrical contexts with various axial and rotation flow rates. Finally, an accurate evaluation of the flow resistance in a rotating shaft has been presented. The rotational friction loss factor in such a hollow-shaft is studied, where the effect of the shaft velocity as well as the coolant flow rate have been accounted for.Motor Design Ltd. and Newcastle University Overseas Research Scholarship (NUORS

Учебно-методическое пособие для студентов специальности 1-53 01 05 «Автоматизированные электроприводы»

Учебно-методическое пособие предназначено для студентов вузов, обучающихся по специальности 1-53 01 05 «Автоматизированные электроприводы». Пособие состоит из 8 разделов, объединенных по тематическому принципу. Каждый раздел включает аутентичный текстовый материал, справочный грамматический материал, а также широкий спектр упражнений, направленных на формирование у студентов речевых навыков и развитие умений профессионально ориентированного иноязычного общения в устной и письменной форме в предполагаемых ситуациях профессиональной деятельности

Improved lumped parameter thermal modelling of synchronous generators

Within the existing available mix of numerical and analytical thermal analysis options, lumped parameter thermal modelling is selected as the operational backbone to develop an improved novel synchronous generator thermal modelling package. The objective is for the creation of a user friendly quick feedback tool, which can serve as a means to make quick machine design thermal calculations and answer customer queries quickly and reliably. Furthermore, thermally improved generator designs will allow for inevitable operational losses to be channelled away from the machine more efficiently. As a result, machine component temperatures will be reduced, allowing lower generator thermal ratings. The end result will be smaller, longer lasting, more efficient generators, with the ability to be adapted with greater ease to particular applications. With the contribution of selected numerical analysis techniques, mainly finite element analysis for the distribution of iron losses, the MySolver thermal modelling package is developed and presented in this thesis. It is this combination of numerical and analytical tools that improves synchronous generator thermal modelling accuracy, but ultimately it is the lumped parameter nature of the thermal models developed that makes MySolver succeed as a reliable quick feedback electrical machine thermal design tool, validated using experimental results for a wide range of operating conditions. The initial part of the thesis analyses the electrical machine thermal modelling techniques available today, indicating advantages and disadvantages associated with each one, and providing a rationale for the selection of lumped parameter modelling to be used by MySolver. The development of the synchronous generator lumped parameter thermal models is detailed, with examples on its construction presented. Subsequently, finite element analysis is utilised to predict the distribution of machine iron losses across the rotor and stator laminations, with the findings applied to MySolver. Furthermore, a study is performed into the lumped parameter discretisation level needed to effectively represent machine windings. MySolver is experimentally verified using experimental data from a fully instrumented synchronous generator and this data is also used to obtain further insight into the temperature distribution within the generator. In the final part results are evaluated and the use of MySolver for modelling and optimising electrical machines is discussed. Finally, appropriate conclusions on the work presented are drawn