Asynchronous machines are considered nowadays the most commonly used electrical machines, which are mainly used as electrical induction motors. Starting the induction motor is the most important and dangerous step. The theory behind this project is based on representing the real motor by a set of equations and values in Matlab using the subsystem feature, forming a corresponding idealistic motor in a way where all the physical effects are similar. The motor is started under different loads in two methods: Direct and Soft starting. Each method is studied and discussed using supporting simulation of currents, torque, speed, efficiency and power factor curves.

Variable speed drive technology has advanced dramatically in the last 10 years with the advent of new power devices. In this study, a three phase induction motor drive using Insulated Gate Bipolar Transistors (IGBT) at the inverter power stage is introduced to implement speed and position control for the revolving stage in the Frederic Wood Theatre This thesis presents a solution to control a 3-phase induction motor using the Texas Instruments (TI) Digital Signal Processor (DSP) TMS320F2407A. The use of this DSP yields enhanced operations, fewer system components, lower system cost and increased efficiency. The control algorithm is based on the constant volts-per-hertz principle because the exact speed control is not needed. Reflective object sensors which are mounted on concrete frame are used to detect accurate edge position of revolving stage. The sinusoidal voltage waveforms are generated by the DSP using the space vector modulation technique. In order to satisfy some operating conditions for safe and agreeable operation, a look-up table, which is used to give command voltage and speed signals in software, is applied to limit the maximum speed and acceleration of the revolving stage. Meanwhile, a boost voltage signal is added at the low frequency areas to make the motor produce maximum output torque when starting. A test prototype is then built to validate the performance. Several tests are implemented into the IGBT drive to explore the reason for unacceptable oscillations in IGBT’s gate control signals. Improvement methods in hardware layout are suggested for the final design.

Electric vehicles are a key technology in the reduction of our carbon footprint and this has motivated significant research interest. The electrical traction motor is one of the main areas of research in attempts to further improve electric vehicle performance. The permanent magnet motor is the predominant device in this application because of its high specific torque. However, it has suffered from market speculation in the raw magnet materials which has generated efforts to develop electrical machines which have a high specific torque and do not contain rare earth materials. In the past the induction motor used to be the preferred motor for electric vehicles due to its low costs, low maintenance requirements, mature technology and robustness. The induction motor requires a higher specific torque to make it an alternative to permanent magnet machines. For this reason, this research had the primary aim of improving the specific torque of induction machines by undertaking a detailed review of the motor design because this process has conventionally focussed on the requirements for industrial applications. The first stage of the work presented in this thesis consisted of identifying the designs already in use for this purpose and the potential technologies applicable to the induction motor that could be transferred from other electric traction machines. A full review of the design process was also conducted in order to identify the key areas of the process with special reference to the electromagnetic design which used finite element techniques as the main modelling tool. New induction motor designs were developed which showed potential for improving the specific torque; two of these were selected for further refinement, prototyping and testing. Although these designs were modified to facilitate construction, some major difficulties were still encountered during the prototype rotor manufacture. The test results were used to validate the design process and to identify further improvements in the designs. The issues encountered with the rotor manufacture prototype however lead to some overheating during the experimental testing. Comments about the design experience gained during this research are summarized including suggestions for further research.

Variable speed drive technology has advanced dramatically in the last 10 years with the advent of new power devices. In this study, a three phase induction motor drive using Insulated Gate Bipolar Transistors (IGBT) at the inverter power stage is introduced to implement speed and position control for the revolving stage in the Frederic Wood Theatre This thesis presents a solution to control a 3-phase induction motor using the Texas Instruments (TI) Digital Signal Processor (DSP) TMS320F2407A. The use of this DSP yields enhanced operations, fewer system components, lower system cost and increased efficiency. The control algorithm is based on the constant volts-per-hertz principle because the exact speed control is not needed. Reflective object sensors which are mounted on concrete frame are used to detect accurate edge position of revolving stage. The sinusoidal voltage waveforms are generated by the DSP using the space vector modulation technique. In order to satisfy some operating conditions for safe and agreeable operation, a look-up table, which is used to give command voltage and speed signals in software, is applied to limit the maximum speed and acceleration of the revolving stage. Meanwhile, a boost voltage signal is added at the low frequency areas to make the motor produce maximum output torque when starting. A test prototype is then built to validate the performance. Several tests are implemented into the IGBT drive to explore the reason for unacceptable oscillations in IGBT’s gate control signals. Improvement methods in hardware layout are suggested for the final design. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Electric machines are being deployed in industrial applications where previously only mechanical systems were considered, as environmental concerns from burning fossil fuels and energy costs are becoming a more dominant factor in system design considerations. Electric machines offer greater operational flexibility and typically higher efficiencies. There has therefore been a growing demand to develop electric machines to replace traditional mechanical systems in a number of industrial applications. One such suitable electric machine topology is the 'direct-drive' machine. These machines can be used where implementation does not require a high operating speed, therefore eliminating the necessity of a gearbox. Furthermore, direct-drive machines offer a number of advantages including reductions in through-life costs, noise and vibration, and overall system volume. This thesis explores the development of direct-drive rim-driven machines, constructed by integrating a propeller with the electric machine that is driving it, by mounting the machine directly around the outside of the propeller. A novel machine topology was developed by integrating a conducting-can onto the rotor structure capable of producing induction torque, to create a motor that can start directly from the main electric supply. This eliminated the need for a power electronic converter, gearbox and complicated drive shafts arrangement, for use in applications where only a low duty cycle of operation was required such as secondary propulsion systems for marine applications or where safety and reliability is of significant importance. A number of other industrial applications that may benefit from this canned rim-driven topology were also identified including seal-less pumps and 'run-of-the-river' generators. Permanent-magnet and induction motor topologies operating in fluid environments were investigated, using finite element analysis and thermal analysis techniques, to examine and optimise the design of the rim-driven topology for a specific operational requirement, in each industrial application area identified. A 30 kW canned line-start rim-drive induction motor was designed and developed for use as a bi-directional thruster on-board a tidal stream turbine. A novel induction motor topology was developed utilising only a conducting-can on the rotor, which eliminated the need for a traditional squirrel-cage, due to the ratio of the relatively large mean air-gap diameter to the small output power requirement; creating a simple yet reliable direct-drive canned induction motor. The design of this motor was manufactured and successfully tested to validate the design process.

The induction motor is a highly utilised electrical machine in industry, with the nuclear industry being no exception. A typical nuclear power station usually contains more than 1000 motors, where they are used in safety and non-safety application. The efficient and fault-free operation of this machine is critical to the safe and economical operation of any plant, including nuclear power stations. A comprehensive literature review was conducted that covered the functioning of the induction machine, its common faults and methods of detecting these faults. The Condition Based Maintenance framework was introduced in which condition monitoring of induction machines is an essential component. The main condition monitoring methods were explained with the main focus being on Motor Current Signature Analysis (MCSA) and the various methods associated with it. Three analysis methods were selected for further study, namely, Current Signature Analysis, Instantaneous Power Signature Analysis (IPSA) and Motor Square Current Signature Analysis (MSCSA). Essentially, the methodology used in this dissertation was to study the three common motor faults (bearings, stator and rotor cage) in isolation and compare the results to that of the healthy motor of the same type. The test loads as well as fault severity were varied where possible to investigate its effect on the fault detection scheme. The data was processed using an FFT based algorithm programed in MATLAB. The results of the study of the three spectral analysis techniques showed that no single technique is able to detect motor faults under all tested circumstances. The MCSA technique proved the most capable of the three techniques as it was able to detect faults under most conditions, but generally suffered poor results in inverter driven motor applications. The IPSA and MSCSA techniques performed selectively when compared to MCSA and were relatively successful when detecting the mechanical faults. The fact that the former techniques produce results at unique points in the spectrum would suggest that they are more suitable for verifying results. As part of a comprehensive condition monitoring scheme, as required by a large population of the motors on a nuclear power station, the three techniques presented in this study could readily be incorporated into the Condition Based Maintenance framework where the strengths of each could be exploited.

The aim of this master thesis is optimization of the rotor in the terms of efficiency. An analysis of the effects of rotor parameters is performed by RMXPRT. A genetic algorithm is created to find the optimal solution. Solutions are evaluated and adjusted according to the results. Measurements on the actual machine are performed and evaluated to verify the functionality of the simulation models.

<p> The speed of a squirrel-cage induction motor is controlled by varying the supply frequency. The design of an SCH controlled inverter, using gating from a logic unit to give a variable-frequency power-level output, is described.</p> / Thesis / Master of Engineering (MEngr)

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