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Energy resources are under tremendous pressure with society’s ever increasing need for electricity. However, resources are becoming scarce and the effect of our power generation on the environment is cause for concern. The cost of electricity is also increasing and thus the need to reduce energy consumption is apparent. Most electrical energy generated is consumed by electric motors. Most of these motors are induction motors because they are reliable, efficient and durable. Though these motors are highly efficient, there is still room for improvement when the strain on electrical energy is taken into account. Constructing motors with better efficiency can result in a reduction in energy consumption and cost savings to the consumer. One method of increasing a motor’s efficiency is to use permanent magnets in the construction of the motor’s core. Permanent magnets eliminate the excitation losses experienced by induction machines, thereby increasing the motor’s efficiency. A retrofit design is considered because of the ease of manufacturing for motor suppliers and the ability to apply the solution to existing operating induction machines. The prototype will lay the foundation for future optimisation strategies. The optimised design should provide improved efficiency with a minimum effect on the motors already operating in industry. The design process followed uses the design principles for inductions machines and for sizing permanent magnets. The design is then verified through the use of finite element method software packages, FEMM and ANSYS Maxwell®, and validated by performance testing. A comparison is drawn between the calculated results and the results determined from the performance analysis. The retrofit design performed as expected during the testing with some discrepancies in final values attributed to the manufacturing process. However, the efficiency is lower than designed and requires the implementation of machine optimisation strategies. / MSc (Electrical and Electronic Engineering), North-West University, Potchefstroom Campus, 2015

Energy resources are under tremendous pressure with society’s ever increasing need for electricity. However, resources are becoming scarce and the effect of our power generation on the environment is cause for concern. The cost of electricity is also increasing and thus the need to reduce energy consumption is apparent. Most electrical energy generated is consumed by electric motors. Most of these motors are induction motors because they are reliable, efficient and durable. Though these motors are highly efficient, there is still room for improvement when the strain on electrical energy is taken into account. Constructing motors with better efficiency can result in a reduction in energy consumption and cost savings to the consumer. One method of increasing a motor’s efficiency is to use permanent magnets in the construction of the motor’s core. Permanent magnets eliminate the excitation losses experienced by induction machines, thereby increasing the motor’s efficiency. A retrofit design is considered because of the ease of manufacturing for motor suppliers and the ability to apply the solution to existing operating induction machines. The prototype will lay the foundation for future optimisation strategies. The optimised design should provide improved efficiency with a minimum effect on the motors already operating in industry. The design process followed uses the design principles for inductions machines and for sizing permanent magnets. The design is then verified through the use of finite element method software packages, FEMM and ANSYS Maxwell®, and validated by performance testing. A comparison is drawn between the calculated results and the results determined from the performance analysis. The retrofit design performed as expected during the testing with some discrepancies in final values attributed to the manufacturing process. However, the efficiency is lower than designed and requires the implementation of machine optimisation strategies. / MSc (Electrical and Electronic Engineering), North-West University, Potchefstroom Campus, 2015

A functioning prototype test motor with Hall-sensor feedback has been built, and the test results show that the motor performance in terms of speed ripple is well within the specified demands. The temperature demands however, have not been fully met. The minimum operating temperature of the sensor was specified to -55◦C by Saab, and the sensors found on the market has a minimum operating temperature of -40◦C. There was also an operation error, the reason of which could either be failure of the drive unit to deliver enough current, or the stator magnetic field strength being too strong for the sensors to reliably detect the rotor magnets when a sufficiently strong current is run through the stator windings. For the purpose of investigating this error it is proposed to conduct tests with a drive unit that can deliver currents over 5 A. / SWE Demo

Well reported problems around air quality and climate change, together with the energy crisis resulting from finite fossil fuel resources is motivating all the automotive manufacturers to develop new propulsion systems through electrification and hybridisation. The range extended electric vehicle (REEV) is one of these solutions that seeks a practical compromise between the on-board battery size and the one-charge driving range. The auxiliary power unit (APU) is the key component in a REEV and is designed to maintain the battery charge for long distance trips. Since the APU does not propel the vehicle, it only requires a small capacity engine with low-cylinder-count. This type of engine exhibits severe speed fluctuations due to its low firing frequency. As the engine and the M/G are isolated from the vehicle driving wheels, it is possible to use the electric machine to deliver a counteracting torque to the engine reducing the resultant torque spikes and thus the system speed oscillation but likely to increase the electric losses. This research work aims to minimise the speed fluctuation balanced against the extra losses introduced. A Dynamic Torque Control (DTC) strategy was designed and tested on an APU using a novel approach to achieve this target. The system components were modelled individually regarding to the prototype system specifications, which is developed within a collaborative R&D project. The empirical engine model was calibrated with extensive bench testing data to recreate the in-cycle torque waveforms. The motor/generator was modelled as a novel hybrid between an analytical model and an FEA model which allowed the winding inductance variation due to the current rise to be included in the model. This approach was designed to replicate the electric machine performance with high fidelity whilst keeping the computational time and cost low. With the help from the system model, the DTC torque demand patterns were designed based on detailed analysis of the contribution factors of the speed fluctuation and the electric machine losses. A unique Pareto Curve of the speed fluctuation reduction and the electrical loss was identified during the analysis and allowed the optimal demand pattern to be developed for a given torque capability electric machine. The simulation results showed that the system in-cycle speed fluctuations could be reduced by 16.4% and 19.11% at 2000rpm full load and 4500rpm full load condition respectively while the electric specific fuel consumption (ESFC) rose by 2.26% and 1.35% at the same operation points. The DTC strategy was implemented in the prototype APU and successfully tested on the rig at 2000rpm and 4500rpm. A reduction in the speed oscillation and the ESFC increase consistent with the simulation results were observed. The simulation estimates on ESFC was proved within an error of 2.19%. This research improves the insight into the mechanisms that are responsible for increased losses when dynamic torque control is used and develops an optimisation approach which takes account of these factors. When an electric machine, which does not have the same instantaneous peak torque capability as the engine, is used in an APU, a better compromise between speed fluctuation smoothing and system efficiency can be achieved.

Because of several advantages, e.g. compact structure, high air-gap flux density, and high torque capability, the PM synchronous motor plays an important role in recent years. The basic principle of controlling a PMSM is based on vector control. The control performance is influenced by factors as the plant parameter variations, the external load disturbances, and the unmodeled or nonlinear dynamics. In the thesis, we apply a recently proposed robust 2DOF configuration to designing controllers for PMSM to achieve the robust asymptotical tracking under perturbations in both the motor and the controllers. Two design methods are adopted to implement the desired controllers, i.e. the linear algebraic method and the design method. The effect of the well-known internal model principle is addressed in the former design method. The merit of the latter design method is that both time and frequency domain design specifications can be easily included in the design procedure. Computer simulation results are displayed to illustrate the advantages of our designs.

When using an intermittent source of energy such as wind power together with a synchronous machine a frequency converter system is needed to decouple the generator from the grid, due to the fluctuations in wind speed resulting in fluctuating electrical frequency. The aim of this master's thesis is to investigate how different types of rectification methods affect permanent magnet synchronous machines of different saliency ratios. A literature study was carried out to review the research within the area and to acquire the necessary knowledge to carry out the work. Two simulation models were created that include a permanent magnet synchronous generator driven by a wind turbine and connected to the grid via a frequency converter, where one model utilizes active rectification and one utilizes passive rectification. The simulation models were verified by carrying out an experiment on a similar setup, which showed that the simulation results coincide well with the results of the experiment. The results of the simulation study were then used to compare the rectification systems as well as investigate the affect that rotor saliency has on the system. It was shown that the active rectification provided a higher efficiency than the passive rectification system, however the saliency of the rotor had little effect on the system

The goal of this thesis was to evaluate sensors and motor speed control methods for BLDC/PMSM motors in Aerospace applications. The sensors and methods were evaluated by considering accuracy, robustness, cost, development gain and parameter sensitivity. The sensors and methods chosen to simulate were digital Hall sensors and sensorless control of BLDC motors. Using Matlab Simulink/Simscape some motor speed control methods and motor speed estimation methods were simulated using the Hall sensors and sensorless control as a basis. It was found that the sensorless control methods for BLDC motors couldn't estimate the speed accurately during dynamic loads and that the most robust and accurate solution based on the simulations was using the digital Hall sensors for both speed estimation and commutation and this was tested on a hardware setup.

The thesis deals with the description of PMSM and BLDC motors as well as the way of their control. In addition, the thesis deals with the description of the instruments of National Instruments, DAQ, CompactRIO and PXI. The details of the user module's production in the CompactRIO device, both hardware and software, are specified in the paper. The following is a description of the proposed CompactRIO module.

Variable speed motor drives are being rapidly deployed for a vast range of applications in order to increase efficiency and to allow for a higher level of control over the system. One of the important areas within the field of variable speed motor drives is the system's operational boundary. Presently, the operational boundaries of variable speed motor drives are set based on the operational boundaries of single speed motors, i.e. by limiting current and power to rated values. This results in under-utilization of the system, and places the motor at risk of excessive power losses. The constant power loss (CPL) concept is introduced in this dissertation as the correct basis for setting and analyzing the operational boundary of variable speed motor drives. The control and dynamics of the permanent magnet synchronous motor (PMSM) drive operating with CPL are proposed and analyzed. An innovative implementation scheme of the proposed method is developed. It is shown that application of the CPL control system to existing systems results in faster dynamics and higher utilization of the system. The performance of a motor drive with different control strategies is analyzed and compared based on the CPL concept. Such knowledge allows for choosing the control strategy that optimizes a motor drive for a particular application. Derivations for maximum speed, maximum current requirements, maximum torque and other performance indices, are presented based on the CPL concept. High performance drives require linearity in torque control for the full range of operating speed. An analysis of concurrent flux weakening and linear torque control for PMSM is presented, and implementation strategies are developed for this purpose. Implementation strategies that compensate for the variation of machine parameters are also introduced. A new normalization technique is introduced that significantly simplifies the analysis and simulation of a PMSM drive's performance. The concepts presented in this dissertation can be applied to all other types of machines used in high performance applications. Experimental work in support of the key claims of this dissertation is provided. / Ph. D.