With the increasing environmental impact from the automotive industry, electric vehicles become more and more popular. This combined with the great breakthroughs in fast electronics the switched reluctance motor (SRM) has again gained popularity in recent years. Due to its cheap and rugged construction it is a good alternative to the permanent magnet motors and to the induction motor. The ́two main problems holding the SRM back are torque ripple and the acoustic noise generated from it. A lot of research is currently being performed in order to find a solution to these issues. This thesis has investigated different materials for the rotor in a high speed SRM. Different materials have been evaluated based on both mechanical and magnetic properties. This is done through simulations of the forces acting on the rotor combined with simulations of the magnetic field. The forces are simulate in the DASSULT SYSTEMS ABAQUS program and the magnetic field is simulate using AVL FIRE. Three different kinds of alloys are investigated, two different cobalt alloys are simulated as well as a silicon alloy with pure iron as a reference. The results show that the material needs to have a yield strength of at least 349 MPa to withstand the forces affecting the rotor. And that by using the high purity cobalt-iron alloy the generated torque could be increased with up to 20.9%, but with a cost increase of 3151.9% compared to the silicon alloy.

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Switched reluctance machines (SRMs) are gaining increasing interest in industrial applications due to their low manufacturing cost, simple and robust structure, excellent fault-tolerant capability, and reliable operation in high-temperature operating environments. However, the inherent pulsative torque and radial force lead to the well-known torque ripples and acoustic noise issues. Although there are numerous advanced methods to address the above two issues, the high nonlinearity inevitably brings difficulties in controlling the SRMs. Since the linear SRM voltage and toque equations are simple, it would be beneficial to explore the control algorithm by using such simple linear model. The application of the linear torque model is firstly explored. To utilize such simple model, the connections between the linear toque model and the nonlinear torque model are built through the mapping. The features of these mapping curves are studied in detail. Applying the linear torque equation to generate the reference currents in the optimization-based torque sharing function method shows a significant reduction of the time consumption in solving the bi-optimization problem. Later, the complete equivalent linear SRM model is constructed by introducing the linear voltage equation and corresponding mapping. Since the linear model is easy to predict the behaviour of SRMs, it is beneficial to apply such model in the model predictive torque control (MPTC) methods. The application of the equivalent linear model in the finite control set (FCS) MPTC method shows a low computational burden and occupies less storage space. Besides, the improved switching table in the proposed FCS MPTC method also enhances the torque control performance in high-speed operation conditions. To further reduce the torque ripples, the continuous control set (CCS) MPTC method is developed based on the constructed equivalent linear SRM model. The impossibility in analytically solving the optimization problem in the CCS MPTC method if using the original nonlinear SRM model is innovatively addressed by using the equivalent linear SRM model and properly modifying the cost function. Extensive simulation and experimental results prove the low-ripple feature of the proposed CCS MPTC method in a wide speed range. The high nonlinearity also makes the current control of SRM drives difficult. An intersection-method-based current controller is presented to ensure good current tracking performance for SRMs. The employed adaptive flux-linkage observer makes this current controller show robust performance when there is a deviation on the employed flux-linkage characteristics. Finally, the key but unmeasurable radial force information for the advanced acoustic reduction method is reconstructed based on the measured flux-linkage curves and some core relationship. This core relationship, which is between the square root of the radial force and the flux-linkage, is explored in detail. Simulation results reveal that the proposed method shows good radial force estimation accuracy when there is even 50% airgap length variation. / Thesis / Doctor of Philosophy (PhD)

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The electric vehicle (EV) market is experiencing growth at an exponential rate, forcing automotive manufactures to invest in powertrain electrification. Manufactures are seeking low cost alternatives for electric propulsion motor technologies with switched reluctance motors (SRMs) having tremendous potential. The performance characteristics of SRMs designed for EV propulsion applications have yet to be experimentally verified. In this thesis, the operation of a 24/16 propulsion SRM specifically designed for a hybrid electric vehicle will be verified with a theoretical model and experimentally. The results are analyzed to gain further understanding of the factors affecting propulsion SRM operation. Two distinct theoretical models of a SRM are presented where one includes the effects of mutual coupling between two excited phases. The theoretical models and the experimental results indicate that for high power density SRMs, designed for propulsion applications, the effects of mutual coupling cannot be ignored. The motor is experimentally tested using a dynamometer machine. A test plan is presented which tests the motor at a wide speed and torque range suitable for EV applications. The testing procedure attempts to segregate the motor losses similar to international standards for induction machines and permanent magnet machines; however, these methods prove invalid due to the non-sinusoidal current in SRMs. Torque ripple minimization is highlighted to reduce the risk of detrimental speed fluctuation during motor testing with careful attention to thermal limitations. The SRM is tested using PWM current control as the baseline control method because hysteresis control is proven to be challenging for the tested SRM. The work presents many challenges associated with the testing and characterization of SRMs for propulsion applications; however, new research findings illustrate the potential of future improvements in propulsion SRM design and operation. / Thesis / Master of Applied Science (MASc)

A new hybrid machine having variable reluctance and permanent magnets (PMs) is presented. The machine makes use of the features of a PM machine and variable reluctance machine. The resulting machine is doubly salient and has a structure free of flux reversals. Unlike conventional doubly salient permanent magnet machines (DSPMs), the one proposed in this report is driven by unipolar currents and uses an asymmetric converter which is used to drive switched reluctance machines. The reason to have a new hybrid machine without the drawbacks of conventional flux-reversal-free-stator SRMs and conventional DSPMs is also described. Conventional doubly salient permanent magnet machines which are driven by alternating currents, do not use reluctance torque and have flux reversals in the stator iron. Homopolar flux at the peak flux density lowers hysteresis and eddy-current loss, since the machine's core operates in only one magnetizing quadrant. Due to unbalanced forces in conventional stator-flux-reversal-free machines, their deployment in industrial and end-user applications has been hindered. The presented hybrid machine has balanced radial forces. Therefore, it maintains the advantages of conventional stator-flux-reversal-free machines while shedding its disadvantages. The proposed machine has significantly increased power density and is more electromechanically efficient than its predecessor. A experimental prototype motor has been designed and built. Its static torque characteristics correlated well with predicted data. Experimental operation of the drive under open loop speed control shows the efficiency to be 90.8% under non-ideal driving conditions. In the current energy conscious environment and market, this motor because of its high efficiency has a significant role in reducing the energy consumption in household, industrial and automotive applications requiring electric motors. / Ph. D.

Demand for energy-saving variable speed drives in low-cost, high-volume appliances has increased due to energy and environmental concerns and hence the need to comply with new regulations. Switched reluctance motor (SRMs) have been considered by many as attractive alternatives for brush commutated motors or permanent magnet brushless dc motors (PMBDCMs) in such cost-sensitive applications. The SRMs' unique features such as simple and fault-tolerant structure and unidirectional flow of their phase currents endow them with the possibility of various configurations on both machine and converter topologies for different applications. In the present study, three different variable-speed motor drive systems are proposed, studied, and implemented for their deployment in low-cost, high-volume applications with the power rating of 1.5kW or less. Two different two-phase SRMs and three different power converters are employed to realize three different low-cost drive systems. The first drive system is realized using a novel converter requiring only a single-controllable switch and an asymmetric two-phase 8/4 SRM capable of self-starting and four-quadrant operation. The second drive system is realized using another novel converter requiring two controllable switches, that way to achieve better control and utilization of the asymmetric 8/4 motor. The target applications for both drive systems are low power, low performance drives such as fans, hand tools, small appliances, etc. The third system is realized using a high-speed two-phase 4/2 SRM and a split ac source converter, which is designed for high-speed applications such as vacuum cleaners, ultracentrifuges, etc. The control and design aspects for each drive system are studied. Selection of optimal firing angles and optimal number of winding turns are also investigated. All of the drive systems are first demonstrated on the position sensor-based speed-control scheme. To make the drive system even more cost-competitive, operation without the position sensor using the novel parameter insensitive sensorless control scheme is proposed and implemented. Concept, analysis, simulation, and experimental verification of the proposed sensorless scheme are discussed in detail. / Ph. D.

High performance current control is critical to the success of the switched reluctance motor (SRM). Yet high motor phase nonlinearities in the SRM place extra burden on the current controller, rendering it the weakest link in SRM control. In contrast to linear motor control techniques that respond to current error, the deadbeat controller calculates the control voltage by the current command, phase current, rotor position and applied phase voltage. The deadbeat controller has demonstrated superior response in three-phase inverter current control, PM motor current control, and other relatively linear control applications. This study will investigate the viability and performance of a deadbeat controller for the highly nonlinear SRM. The need for an accurate deadbeat control model first motivates the investigation of experimental inductance measurement techniques. A deadbeat control law is then proposed through multiple revisions to demonstrate the benefit of the numerical method chosen to derive the controller and a current predictor that accounts for processor latency and PWM delay. The practical problems of loop delay, feedback noise, feedback filtering, and deadbeat controller parameter sensitivity are investigated by linear analysis, simulation, experimental implementation and nonlinear model analysis. Simulation and implementation verify deadbeat performance and various measures of transient performance are presented. To address the problem of SRM model error the study ends with a brief discussion of adaptive deadbeat control modifications for possible future research. / Master of Science

In the emergence of switched reluctance motors to the commercial market, two-phase motors have received relatively little attention. Higher power and industrial applications have focused on the use of three and occasionally four phase machines, while low cost applications demanding only modest performance have largely been the domain of single phase machines. By contrast, while two phase systems have been the subject of occasional studies, they have not been widely applied. Two phase systems represent a compromise between the higher cost but higher performance three phase machines, and the lower cost but lower performance single phase systems. They do not suffer from the same magnitude of peak to peak torque ripple that single phase machines experience due to their wide zero torque arcs. Yet two phase systems keep a relatively low component count in their power-converter designs. The primary drawback to two phase motors is the difficulty of torque production at startup speeds. Although sizably reduced from single phase machines, the zero torque regions in two phase machines can still result in rotor lock unless steps are taken to circumvent them. These steps can include measures such as: placement of permanent magnets or other means to ensure the rotor is positioned outside of these zero torque regions when at rest, mechanically spinning the motor before energizing the phase windings on startup, shaping of the rotor or stator poles to extend the positive torque regions of each phase, or use of the machines mutual inductance with both phases energized to produce enough torque to initiate motion. This project is intended to develop a variable speed controller for a 4:6 two-phase switched reluctance motor. The motor is to operate in all four quadrants, and is to demonstrate self starting capability. The controller is also supposed to produce signals needed to operate the motor with multiple converter designs. Two different converter designs will be built and tested with the converter. One makes use of a single switch and two diodes per phase, the other has one switch and one diode per phase plus a common switch and common diode shared by all phases. There are many possible applications of the system being developed in this project. Any application needing four quadrant operation while still being constrained by low cost requirements would be ideal. Some examples include washing machines, power tools, and low power industrial applications. / Master of Science

This master’s thesis is focuses on the reluctance motor, especially on the design of the rotor. It shows the development of the construction of rotors of reluctance motors. Furthermore, it shows the principle of reluctance machine and its basic mathematical description and the principle of improving the machine parameters by inserting permanent magnets into the rotor. It offers an overview of patents available from 2000 to present. Also it deals with the design of the rotor with permanent magnets for stator of induction motor.