Methods of calculation of magnetic fields and static characteristics of linear step motors for control rod drives of nuclear reactors

The performance of linear step motors (LSMs) which are being developed for control rod drives in nuclear reactors is governed by their static characteristics. The reliability of control rod drive mechanisms and the safety of the reactor depend on reliable performance of these motors. The authors describe methods of calculation of magnetic fields and static characteristics of LSMs. Two methods have been developed, approximate and accurate. The first method, less computationally intensive, could be used for small currents and weak iron saturation, while the second, based on accurate field modeling, takes into account saturation effects which considerably affect motor performance

Design and Construction Modifications of Switched Reluctance Machines

Although the design principles of the Switched Reluctance Machines (SRMs) are available in different fragments in numerous bibliography positions, there no exists the complex design procedure of whole drive system taking into account the SR Machine, control system and supply device as well. The hybrid design method for SRM drives with application of new analytical calculation methods, finite element method and simulation models is proposed in this thesis. The calculation/design system is characterised by important effectivity and reliability. The new possibilities in analytical determination of saturation effects and core losses under various modes of control, including sensorless method, are also taken into account. The correctness of the proposed design algorithms are verified by laboratory tests made on three motor prototypes manufactured in industry for concrete application. This dissertation provides the elements indispensable for more accurate and complex analysis and design of drives with switch reluctance motors. The elements of electrical motor and control system design as well as the considerations on the choice of supply device and controller subsystems are jointed in the thesis for final receiving of the design tool for considered industrial drive system

Modelling and Control of Switched Reluctance Machines

Today, switched reluctance machines (SRMs) play an increasingly important role in various sectors due to advantages such as robustness, simplicity of construction, low cost, insensitivity to high temperatures, and high fault tolerance. They are frequently used in fields such as aeronautics, electric and hybrid vehicles, and wind power generation. This book is a comprehensive resource on the design, modeling, and control of SRMs with methods that demonstrate their good performance as motors and generators

Modelling and Control of Switched Reluctance Machines

Today, switched reluctance machines (SRMs) play an increasingly important role in various sectors due to advantages such as robustness, simplicity of construction, low cost, insensitivity to high temperatures, and high fault tolerance. They are frequently used in fields such as aeronautics, electric and hybrid vehicles, and wind power generation. This book is a comprehensive resource on the design, modeling, and control of SRMs with methods that demonstrate their good performance as motors and generators

The Flux-MMF diagram technique and its applications in analysis and comparative evaluation of electrical machines

The thesis describes a new technique, called the flux-MMF diagram technique, for analysis and comparative evaluation of electrical machines. The technique has evolved from the principle of virtual work, and the -i diagram, used commonly in designing switched reluctance machines and relays. Several applications of this technique are demonstrated in the thesis, supported by experimental validation. These are, the prediction of electromagnetic and cogging torque ripple, modelling of the effect of skew on torque and torque ripple, modelling of the variation of torque constant due to saturation, and comparative evaluation of different types of electrical machines. The thesis shows that the technique can be applied successfully in analysis of a wide variety of electrical machines. These include conventional machines such as the DC commutator, PM brushless AC, Interior PM, and the synchronous reluctance machine; as well as non-conventional machines such as the switched reluctance, PM brushless DC, and the doubly-salient PM machine. The technique has been implemented in a finite-element software, with the help of a link program which links the FE software with the dimensioning or sizing software, such as PC-BDC, produced by the SPEED Laboratory. The link program serves as a vital means of shortening the time it takes to analyse a new design in an FE software, by several orders of magnitude. The thesis also describes a new brushless doubly-salient permanent-magnet machine, called the flux-reversal machine. The design and fabrication process, and the experimental results are presented for a prototype single-phase, high-speed flux-reversal generator. The performance analysis of the prototype based on the flux-MMF diagram technique is included, and this validates its capability in analysing new and non-conventional machines, which cannot be analysed using the classical means

Synchronous reluctance motors with fractional slot-concentrated windings

PhD ThesisToday, high efficiency and high torque density electrical machines are a growing research interest and machines that contain no permanent magnet material are increasingly sought. Despite the lack of interest over the last twenty years, the permanent magnet-free synchronous reluctance machine is undergoing a revival and has become a research focus due to its magnet-free construction, high efficiency and robustness. They are now considered a potential future technology for future industrial variable speed drive applications and even electric vehicles. This thesis presents for the first time a synchronous reluctance motor with fractional slot-concentrated windings, utilizing non-overlapping single tooth wound coils, for high efficiency and high torque density permanent magnet-free electric drives. It presents all stages of the design and validation process from the initial concept stage through the design of such a machine, to the test and validation of a constructed prototype motor. The prototype machine utilizes a segmented stator core back iron arrangement for ease of winding and facilitating high slot fill factors. The conventional synchronous reluctance motor topology utilizes distributed winding systems with a large number of stator slots, presenting some limitations and challenges when considering high efficiency, high torque density electrical machines with low cost. This thesis aims to present an advancement in synchronous reluctance technology by identifying limitations and improving the design of synchronous reluctance motors through development of a novel machine topology. With the presented novel fractional slot concentrated winding machine design, additional challenges such as high torque ripple and low power factor arise, they are explored and analysed - the design modified to minimise any unwanted parasitic effects. The electrical and electromagnetic characteristics of the developed machine are also explored and compared with that of a conventional machine. A novel FEA post-processing technique is developed to analyse individual air-gap field harmonic torque contributions and the machines dq theory also modified in order to account for additional effects. The developed machine is found to be lower cost, lower mass and higher efficiency than an equivalent induction or conventional synchronous reluctance motor, but does suffer higher torque ripples and lower power factor. The prototype is validated using static and dynamic testing with the results showing a good match with finite element predictions. The work contained within this thesis can be considered as a first step to developing commercial technology based on the concept for variable speed drive applications.Financial assistance was provided by was provided by the UK Engineering and Physical Sciences Research Council (EPSRC) in the form of a Doctoral Training Award and additional financial assistance was kindly provided by Cummins Generator Technologies, Stamford, UK, through industrial sponsorship of this wor

Aspects of magnetisation and iron loss characteristics in switched-reluctance and permanent-magnet machines

In the first section, the magnetisation characteristics of the switched-reluctance motor are examined. Measurements have been carried out using both static and dynamic test methods. The test data has been compared with simulation results from analytical design programs and finite element models. The effects of mutual coupling on the magnetisation characteristics are investigated through measurement and simulation. Results show that the degree of mutual coupling is strongly dependent on the winding arrangement of the machine. In the next section, the difficulties in measuring the properties of permanent-magnet machines are discussed in detail, and solutions to common problems proposed. The measurement and analysis methods used for the switched-reluctance motor are further developed for analysis of permanent magnet machines. Techniques for determining the variation in synchronous reactances and permanent magnet flux are presented. Finite element simulations are used to show the variation of magnet flux under loading, a condition ignored in classical analysis methods. The final section discusses the analysis of magnetisation characteristics of electrical sheet steels. Comparison is made between measurements carried out on single sheet tester and Epstein square test rigs. The iron losses of a typical non-grain-orientated steel are measured under both sinusoidal and nonsinusoidal flux density conditions. The iron losses are shown to increase significantly when higher harmonic components are introduced to the flux density waveform. The difficulties in modelling the nonlinear iron loss characteristics of electrical steels are considered