Switched Reluctance Machines (SRMs) are gaining more attention due to their simple and rugged construction, low manufacturing cost, and high-speed operation capability. An electromagnetic model of the machine is needed in the design and analysis processes. The required accuracy level of the model depends mainly on the application. Designing an SRM is an iterative process. Usually, finite element method (FEM) is employed in all design stages, which might require extensive computation burden. The magnetic equivalent circuit (MEC) method is an alternative for typical FEM. MEC models require less computational resources and they can help determine the electromagnetic performance with a reasonable accuracy. The conventional MEC method can be challenging when modifying the motor geometry while conducting dynamic analysis with current control. This thesis proposes a reluctance mesh-based MEC model for SRMs that can overcome those challenges. Reluctance mesh-based MEC models are developed for 3-phase 6/4, 6/16, 12/8 SRMs and 4-phase 8/6, 8/10, and 16/12 SRMs. The implemented MEC-based modeling method is validated using FEM and experimental results. Acoustic noise and vibration is one of the shortcomings of an SRM. The radial force density in the airgap should be calculated before analyzing and mitigating acoustic noise and vibration. This thesis proposes a radial force density calculation method for SRMs using the proposed MEC model. Fourier series is used to calculate the harmonics of the radial force density. The results obtained from the MEC model are verified using FEM models. SRM is a promising candidate for electric propulsion systems. In the design process of an SRM, the motor geometry needs to be determined. This thesis applies the proposed MEC technique to the design process of a 3-phase 12/16 SRM for a high lift motor in the NASA Maxwell X-57 electric aircraft. The design is verified using the results computed from FEM. / Dissertation / Doctor of Philosophy (PhD) / Electric motors are utilized in our daily life in various applications such as washing machines, refrigerators, air conditioners, fans, vacuum cleaners, blenders, and many other devices and tools. Motors are widely used in residential, industrial, commercial, and transportation applications. Due to the environmental impact of burning fossil fuels, transportation systems are moving into electrified propulsion. Electric motors with lower cost and higher efficiency are on the path to replacing the traditional combustion engines in vehicles. Among the different electric motors available, switched reluctance motor (SRM) is becoming a promising candidate in future electrified transportation systems due to their simple construction. Developing a motor is a time-consuming and costly task. Therefore, it is essential to determine the characteristics of an SRM before manufacturing it. A mathematical framework is proposed in this thesis to address this problem. The proposed framework is capable of determining the characteristics of an SRM accurately.

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This thesis investigates and determines the design considerations to be addressed when designing switched reluctance machines (SRMs) operating at high surface-speeds and high-loads. A new method is introduced to the traditional machine design procedure that captures all of the mechanical, thermal and electro-magnetic considerations for such electric machines. This method is applicable to any motor design; however, is most suitable for machines with rotors that sustain mechanical stresses near the rotor core material limits. The method begins by using common application specifications to identify the maximum diameter and length of a rotor through a series of structural analyses. Maximizing rotor diameter and axial length enables designers to evaluate a machine's theoretical mechanical and electro-magnetic performance limits. The design method is structured such that the designer must use theoretical limits as a constraint for assessing future design decisions which ultimately influence machine cost and performance. The proposed design method is applied to a case study example typical of a large electric vehicle traction machine, a 22,000rpm, 150 kW switched reluctance machine, while attempting to adhere with design practices commensurate with automotive mass manufacturing. To achieve this, a parallel connected 12/8 pole topology was finally developed. The thesis research suggest that a 440 MPa yield strength, 0.27mm thickness lamination with 30 turn stator coils is sufficient to meet the specification requirements within a prescribed power electronic converter voltage and current constraints, while satisfying material mechanical and thermal considerations. Detailed analysis of AC effects, performance characteristics, thermodynamics, noise and vibration is presented to simultaneously demonstrate and validate the proposed machine design and design method. / Thesis / Doctor of Philosophy (PhD)

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)

Switched reluctance machines are becoming more prevalent in various motor drive applications due to their simple construction, robust design, fault tolerant operation, and relatively low-cost construction. There are nonetheless some drawbacks to the switched reluctance machines operational behavior which limit its potential market penetration. The electromagnetic torque ripple is one of those limitations. However, unlike most four-quadrant variable speed electric motors, switched reluctance machines need additional control considerations to operate in generating mode to maximize power returned while minimizing torque ripple. The goal of this thesis is to explore different control schemes which are used in motoring mode and compare their performance in generating mode for different operational points. Using the lessons learned from the comparisons in generating mode, key optimizations objectives are established to improve the switched reluctance machines performance for generating applications. A multi-objective optimizer is used to select conduction angles using established objectives of maximizing torque and minimizing torque ripple. The proposed generating-specific objectives are compared to the motoring-specific objectives to validate the generating performance improvement for a wide torque-speed range. Finally, a setup is constructed to validate the generating performance of a 3-phase 12/8 SRM using the new optimization objectives and it is compared with conventional objectives. / 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

A microprocessor control scheme for variable speed switched reluctance motor(SRM) drives is discussed. A particular implementation derived from first principles of the SRM is presented. The Intel 8088 microprocessor is used for the design implementation. It is shown that given the control requirements of the SRM like firing different phases according to rotor position and phase currents, a microprocessor controller is a good choice. The controller is economical since it uses standard TTL chips. The slow response at low speeds is also discussed. Experimental results performed on a static inductive load using a simulated position feedback are presented, showing how the current control available at lower speeds is lost at higher speeds, due to limited dc bus voltage. A listing of the controller software with adequate comments and the circuit diagrams are appended. / Master of Science