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)

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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.

The purpose of this study was to evaluate the relationships among field dependency levels, performance on a non-locomotor balancing task both sighted and blindforded, and the acquisition of a complex biplanar motor skill. The participants for this investigation were young (ages 9-17) female gymnasts (n = 17) who had all received at least one year of gymnastics training, and could perform the prerequisite skills required for this experiment. All subjects were given the embedded figures test (EFT) (Witkin, Oltman, Raskin, & Karp, 1971) and a sighted and a blindfolded task on a stabilometer. The subjects, having been taught with a non-visual teaching method, were then given 50 trials of the full twisting back flip (FULL) on the trampoline. The gymnasts were attached to an overhead spotting rig to insure their safety. A single factor model (field dependence-independence) with three levels (high, middle, and low) was used to examine the relationships among variables. An analysis of covariance (ANCOVA) was used to adjust posttest FULL scores to pretest scores and to assess the effects of field dependency levels on the FULL learning which:it:ook place. Multiple correlations were used to examine the relationships among EFT scores, stabilometer time in balance (TIB) and time in balance blindfolded (TIBB) scores, and pretest and posttest FULL scores. From the data analysis it was found that subjects' field dependency levels did not correlate significantly with their pretest or posttest FULL scores, or with the stabilometer measures. A significant relationship was found between pretest and posttest FULL scores (r = .837) and TIB and TIBB scores (r = .541). The following conclusions were drawn from the findings: (1) because of the lack of significant correlations between the FULL and either the EFT or the stabilometer task, the use of either of these measures as a predictor of the rate of learning of the FULL is not warranted; (2) of all the variables used in this investigation, subjects' pretest FULL scores are the best indicators of how rapidly they will learn the FULL, having been taught by the non-visual method. / M.S.

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Call number: LD2668 .T4 1966 F786 / Master of Science

The thesis describes a novel 4-quadrant DC-DC converter, supplied by a 28V DC voltage source, with an output voltage which may be continuously varied between +180V and -180V DC. A prototype 1.2kW DC-DC converter was designed and built, with emphasis given to the optimization of both the converter size and efficiency. This was achieved by means of a computer-based simulation study, which determined the optimal switching frequency and the size of the inductors and capacitors while maintaining a high unit efficiency. Mos-Gated Bimos switches, which feature the advantages of both mosfets and bipolar transistors, were developed to achieve high switching speed during high power operation. A digital-controlled DC servo system based on a 16-bit Intel 8086 microprocessor was designed, to provide both motor speed and position control. Speed and position detection circuits and the structure and the interfacing arrangement of the microprocessor system were designed and constructed. Several control algorithms were developed, including PID Control Algorithm and Current-Limit Control Algorithm. Based on open loop transfer function of the system, derived through mathematical modelling using the State-Space Averaging Method, the constants for the control algorithms were obtained to meet the dynamic performance specified for the system. Computer simulation was carried out to assist with the design of the converter and the control system. It is expected that drives into which the novel converter is incorporated will find many applications in situations where accurate positional control is required, particularly in battery-operated DC-servo system, such as satellite system, robots and some military vehicles.