In recent years, the product life cycle has decreased and demands for new products have emerged due to competition, modern industrial needs and rapidly changing technology. This has necessitated changes in design, development and manufacturing processes to improve the quality and efficiency and to reduce the cost. Computer Aided Design (CAD) helps to meet this challenge both in the design evaluation and product design stages. This thesis contains the development of an interactive software for the optimal design of a motor intended for variable speed applications. The use of finite element analysis methods is proposed as an indispensable part of the CAD system for electrical machine design. An illustration of the method is presented for the design of a switched reluctance motor. / Master of Science

A microcomputer-based data acquisition and control system was designed for the diagnostic monitoring and control of high-speed electric motors. The system was utilized in high-speed bearing life-testing, using an electric motor as a test vehicle. Bearing vibration and outer race temperature were continuously monitored for each ball bearing in the motor. In addition, the stator winding and motor casing temperature were monitored. The monitoring system was successful in detecting an unbalance in the rotor caused by the loss of a small piece of balancing putty. The motor was shut down before any further damage occurred. In a separate test, excessive clearance between a bearing outer race and the motor caused high vibration readings. The motor was monitored until the condition began to deteriorate and the bearing outer race began to spin significantly. Again, the monitoring system powered down the motor before any significant damage occurred. The speed of the motor tested is controlled by a PWM (pulse width modulation) technique. The resulting voltage and current waveforms are asymmetrical and contain high frequency components. Special circuitry was designed and constructed to interface sensors for measuring the voltage and current inputs to a spectrum analyzer. Using frequency and order analysis techniques, the real and reactive power inputs to the three·phase motor were measured. / Master of Science

It can definitely be stated that the results of the experiments show that almost no appreciable adverse effects on the test motor result from six phase rectifier operation, The efficiency was unaffected by rectifier operation, The temperature rise with rectifier operation was roughly within 5°C of that obtained with DC generator input, The commutation was not adversely affected when using the rectifier, These statements apply even when the rectifier is operated at half voltage, a condition giving very much more ripple than the full voltage ripple. / Master of Science

Call number: LD2668 .T4 1960 C42

Thesis (MScEng)--Stellenbosch Universit, 2004. / ENGLISH ABSTRACT: The requirements regarding the quality of engines and vehicles have increased constantly, requiring more and more sophisticated engine testing. At the same time, there is a strong demand to reduce lead time and cost of development. For many years steady state engine testing was the norm using standard principles of power absorption. Since the mid 1980's increasing importance has been attached to the optimisation of transient engine characteristics and the simulation of dynamic real world driving situations on engine test stands. This has led to the use of bi-directional DC or AC regenerative dynamometers a practice now known as dynamic engine testing. Interfacing a computer with vehicle simulation software to an engine on a dynamic test stand and using "hardware in the loop" techniques, enables the simulation of real world driving situations in a test facility. In dynamic engine testing a distinction can be made between simulation testing and transient testing. In simulation testing the set point values are predetermined whereas in transient testing a model generates set point values in real time. Speeds and loads are calculated in real time on the basis of real time measurements. The model can be in the form of a human or driver simulation. This project involved the application of dynamic engine testing to simulating a racing application. It is termed Real Time Full Circuit Driving Simulation System due to the simulation of a race car circling a race track, controlled by a driver model and running the engine on a dynamic test bench in real time using "hardware in the loop" techniques. By measuring the simulated lap times for a certain engine configuration on the test bench in real time, it is possible to select the optimal engine set-up for every circuit. The real time nature of the simulation subjects the engine on the test bench to similar load and speed conditions as experienced by its racing counterpart in the race car yielding relevant results. The racing simulation was achieved by finding a suitable dynamic vehicle model and a three dimensional race track model, developing a control strategy, programming the software and testing the complete system on a dynamic test stand. In order to verify the simulation results it was necessary to conduct actual track testing on a representative vehicle. A professional racing driver completed three flying laps of the Killarney racing circuit in a vehicle fitted with various sensors including three axis orientation and acceleration sensors, a GPS and an engine control unit emulator for capturing engine data. This included lap time, vehicle accelerations, engine speed and manifold pressure, an indicator of driver input. The results obtained from the real time circuit simulation were compared to actual track data and the results showed good correlation. By changing the physical engine configuration in the hardware and gear ratios in the software, comparative capabilities of the system were evaluated. Again satisfactory results were obtained with the system clearly showing which configuration was best suited for a certain race track. This satisfies the modem trend of minimizing costs and development time and proved the value of the system as a suitable engineering tool for racing engine and drive train optimisation. The Real Time Full Circuit Driving Simulation System opened the door to further development in other areas of simulation. One such area is the driveability of a vehicle. By expanding the model it would be possible to evaluate previously subjective characteristics of a vehicle in a more objective manner. / AFRIKAANSE OPSOMMING: Die vereistes om die kwaliteit van enjins en voertuie te verhoog, word daagliks hoër. Meer gesofistikeerde enjintoetse word daarom vereis. Terselfdertyd is dit 'n groot uitdaging om die tydsduur en koste van ontwikkeling so laag as moontlik te hou. Gestadigde toestand enjintoetse, wat op die prinsiep van krag absorpsie werk, was vir baie jare die norm. Vanaf die middel tagtigerjare het die optimering van dinamiese enjinkarakteristieke en die simulasie van werklike bestuursituasies op enjintoetsbanke van al hoe groter belang geword. Die gevolg was die gebruik van twee rigting wisselof gelykstroomdinamometers en staan vandag bekend as dinamiese enjintoetsing. Deur 'n rekenaar met simulasiesagteware aan 'n enjin op 'n dinamiese toetsbank te koppel, word die moontlikheid geskep om enige werklike bestuursituasies van 'n voertuig te simuleer in die enjintoetsfasiliteit. Dinamiese enjintoetse kan opgedeel word in simulasietoetse en oorgangstoestandtoetse. By laasgenoemde genereer 'n "bestuurdersmodel" die beheerwaardes intyds deur te kyk na intydse metings terwyl by simulasietoetse die beheerwaardes vooraf bepaal word. Die "bestuurder" kan in die vorm van 'n persoon of rekenaarsimulasie wees. Die projek behels die toepassing van dinamiese enjintoetse vir renbaansimulasie en staan bekend as'n Intydse, Volledige Renbaansisteem weens die simulasie van 'n renmotor om 'n renbaan, onder die beheer van 'n bestuurdersmodel. Dit geskied terwyl die enjin intyds op 'n dinamiese enjintoetsbank loop en gekoppel is aan die simulasie. Deur die intydse, gesimuleerde rondtetye te analiseer, word die moontlikheid geskep om die enjinkonfigurasie te optimeer vir 'n sekere renbaan. Dit is bereik deur die keuse van 'n gepaste dinamiese voertuigmodel, 'n driedimensionele renbaanmodel, ontwikkeling van 'n beheermodel, programmering van die sagteware en integrasie van die dinamiese enjintoetsstelsel. Die simulasieresultate verkry is gestaaf deur werklike renbaantoetse. 'n Professionele renjaer het drie rondtes van die Killarney renbaan voltooi in 'n verteenwoordigende voertuig wat toegerus was met verskeie sensors o.a. drie as versnellings- en orientasiesensors, GPS en 'n enjinbeheereenheidemmuleerder vir die verkryging en stoor van enjindata. Die sensors het data versamel wat insluit rondtetyd, voertuigversnellings, enjinspoed en inlaatspruitstukdruk. Die korrelasie tussen die simulasie waardes en werklik gemete data was van hoë gehalte. Deur die fisiese enjinkonfigurasie te verander in die hardeware en ratverhoudings in die sagteware, is die vergelykbare kapasiteite van die renbaansimulasie geevalueer. Die resultate was weer bevredigend en die simulasie was in staat om die beste enjinkonfigurasie vir die renbaan uit te wys. Dit bevredig die moderne neiging om koste en ontwikkelingstyd so laag as moontlik te hou. Sodoende is bewys dat die stelsel waarde in die ingenieurswêreld het. 'n Intydse, Volledige Renbaansisteem die skep die geleentheid vir verdere ontwikkeling op verskeie terreine van simulasie. Een so 'n veld is die bestuurbaarheid van 'n voertuig. Deur die model verder te ontwikkel word die moontlikheid geskep om voorheen subjektiewe karakteristieke van 'n voertuig meer wetenskaplik te analiseer.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

Approved for public release; distribution is unlimited / The naval vessels of the future will require lighter, more compact, and more versatile power electronics systems. With the advent of the DC Zonal Electrical Distribution System, more innovative approaches to the conversion of the dc bus power to ac power for motor drives will enhance the efficiency and warfighting capability of tomorrow's ships. This thesis explores the concept of a hybrid dc-ac power converter that combines a hysteresis controlled inverter with a six-step bulk inverter. A six-step bulk inverter is built from discrete components and tested in simulation and hardware. The two inverters are connected in parallel to provide a high-fidelity current source for a three-phase load. The addition of the hysteresis inverter to the bulk inverter adds a closed current loop for more robust control and improves the quality of the output load current. / Major, United States Marine Corps

A thesis submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the Degree of Doctor of Philosophy. / Variable speed motors are achieved by varying the voltage of a DC machine or by varying the frequency of an AC machine, the former method being the simpler of the two. DC motors have the major disadvantage of brushes and commutators which require regular downtime for maintenance, a fact already recognised by Tesla [1] in 1888. Thus the AC motor, in particular the induction motor, is of a more rugged design and does not suffer from the commutator problem of its DC counterpart. Recent advances in the technology of the power electronics used to supply a variable frequency to the motor has allowed the induction motor to be a viable alternative to the DC motor in variable speed applications. Problems have been encountered in industry when an inverter is injudiciously selected to be combined with a motor. Such problems were highlighted by difficulties being experienced with some 400 kW inverter drives. The inverters had been bought from one supplier and the motors from another. When this system was coupled together, there was excessive heating in the motors and the overall plant was only able to operate well below its capacity, incurring a substantial weekly loss of income. The motor and inverter were evidently incompatible, and since the inverter could not be modified, the motor was redesigned to make it less susceptible to the harmonics present in the inverter waveform, These problems have led to the development of a variable speed drive simulation package at the University for use by the local industry which can accurately model the complete system of inverter, motor and its associated load. It is envisaged that this package could be used to predict the performance of a drive system and highlight problems that may occur. To be able to do this, an accurate model of the motor is required. This investigation gives the development of an induction motor model which is suitable . for variable speed drive system simulations. The model accounts for the deep bar effect by using lumped parameter circuits and includes saturation of the leakage paths using only information which is typically available from motor design data. A complete analysis is given of the different lumped parameter models and their suitability for use in this application. The thesis also shows the utilisation of the deep bar model to simulate reswitching transients and double cage motors. The author hopes that the models used in the simulation package wallow industry to predict problems prior to their occurrence, alter the designs and thereby avoid costly remanufacture of the system. / Andrew Chakane 2018