This dissertation aims at developing techniques to achieve high power density in motor drives under the performance requirements for transportation system. Four main factors influencing the power density are the main objects of the dissertation: devices, passive components, pulse width modulation (PWM) methods and motor control methods. Firstly, the application of SiC devices could improve the power density of the motor drive. This dissertation developed a method of characterizing the SiC device performance in phase-leg with loss estimation, and claimed that with SiC Schottky Barrier Diode the advantage of SiC JFET could benefit the motor drive especially at high temperature. Then the design and improvement of the EMI filter in the active front-end rectifier of the motor drive was introduced in this dissertation. Besides the classical filter design method, the parasitic parameters in the passive filter could also influence the filtering performance. Random PWM could be applied to reduce the EMI noise peak value. The common-mode (CM) noise reduction by PWM methods is also studied in this dissertation. This dissertation compared the different PWM methods’ CM filtering performance. Considering the CM loop, the design of PWM methods and switching frequency should be together with the CM impedance. Variable switching frequency PWM (VSFPWM) methods are introduced in the dissertation for the motor drive’s EMI and loss improvement. The current ripple of the three-phase converter could be predicted. Then the switching frequency could be designed to adapt the current ripple requirements. Two VSFPWM methods are introduced to satisfy the ripple current peak and RMS value requirements. For motor control issue, this dissertation analyzed the principle of the start-up transient and proposed an improved start-up method. The transient was significantly reduced and the motor could push to high speed and high power with speed sensorless control. Next, the hardware development of modular motor drive was introduced. The development and modification of 10kW phase-legs and full power test of a typical 30kW modular converter is realized with modular design method. Finally, the techniques developed in this dissertation for high power density motor drive design and control are summarized and future works are proposed.

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Fault tolerant motor drives are becoming more important in safety critical applications. Although a single motor module fault tolerant drive may be sufficient in some applications, this motor drive only offers limited redundancy. This thesis investigated the dual motor module fault tolerant drive system in which two motor modules were connected electrically in phase and on a common shaft provide redundancy and to increase the reliability of the entire drive system. A general phase current mathematical model to produce the desired output torque was developed to minimize copper loss and torque ripple in the motor drive, which is applicable to both sinusoidal and trapezoidal brushless permanent magnet motor types. A detailed fault effect investigation was performed in this thesis and it is concluded that switch short-circuit fault is the most serious fault since it reduces the electromagnetic torque output significantly and generates larger torque ripple in the motor drive due to the presence of large drag torque. Three fault remedial strategies were proposed to compensate the torque loss and to reduce the torque ripple under different faulty conditions. It is concluded from the analytical results that fault remedial strategy 3 is the tradeoff algorithm in which the zero torque ripple factor can be achieved with only a modest increase in copper loss comparing with the minimum possible value. Two practical dual motor module fault tolerant brushless permanent magnet drive test arrangements with different motor structures were developed in this thesis. The computer simulation studies using the MATLAB Simulink were performed to verify the effectiveness of the proposed fault remedial strategies. The efficiency of the motor drive was predicted based on torque loss measurements and the results were verified in the simulation study. The effect of faults on the drive efficiency was investigated as well. The entire fault tolerant motor drive control system was also developed to verify the analytical and simulation results. A fault detection and identification method to detect switch open-circuit faults, switch short-circuit faults, and the winding short-circuit faults was also proposed. Its advantages are the simplicity of the implementation and reduction of the cost of the drive system. The experimental results demonstrated that the proposed fault remedial strategies can be implemented in real time motor control and are effective to compensate the torque loss and reduce the torque ripple. / Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 2008

The automobile industry is moving fast towards Electric Vehicles (EV); however this paradigm shift is currently making its smooth transition through the phase of Hybrid Electric Vehicles. There is an ever-growing need for integration of hybrid energy sources especially for vehicular applications. Different energy sources such as batteries, ultra-capacitors, fuel cells etc. are available. Usage of these varied energy sources alone or together in different combinations in automobiles requires advanced power electronic circuits and control methodologies. An exhaustive literature survey has been carried out to study the power electronic converter, switching modulation strategy to be employed and the particular machine to be used in an EV. Adequate amount of effort has been put into designing the vehicle specifications. Owing to stronger demand for higher performance and torque response in an EV, the Permanent Magnet Synchronous Machine has been favored over the traditional Induction Machine. The aim of this thesis is to demonstrate the use of a multi level inverter fed Brush Less Direct Current (BLDC) motor in a field oriented control fashion in an EV and make it follow a given drive cycle. The switching operation and control of a multi level inverter for specific power level and desired performance characteristics is investigated. The EV has been designed from scratch taking into consideration the various factors such as mass, coefficients of aerodynamic drag and air friction, tire radius etc. The design parameters are meant to meet the requirements of a commercial car. The various advantages of a multi level inverter fed PMSM have been demonstrated and an exhaustive performance evaluation has been done. The investigation is done by testing the designed system on a standard drive cycle, New York urban driving cycle. This highly transient driving cycle is particularly used because it provides rapidly changing acceleration and deceleration curves. Furthermore, the evaluation of the system under fault conditions is also done. It is demonstrated that the system is stable and has a ride-through capability under different fault conditions. The simulations have been carried out in MATLAB and Simulink, while some preliminary studies involving switching losses of the converter were done in PSIM.

In vector control of induction motors it is essential to know the parameters of the motor. Known approaches to this problem have some drawbacks. This thesis work is planned to develop solutions to the existing problems. The proposed solutions will be implemented and tested.

The objective of this dissertation is to study the switched reluctance machine (SRM) electromagnetic design and optimization. The research of electric machines is mostly driven by the motivation for higher efficiency and lower cost. The demands for high-performance electric machines also come from the development of emerging industries, such as electric vehicles (EV), hybrid electric vehicles (HEV), renewable energy conversion, energy storage and precision manufacturing. The additional requirements for those applications include volume, weight, speed, torque, reliability, fault tolerance capability, etc. The focus of the research effort is on the high speed and high torque applications, where the SRM stands out compared to other types of machines. The conventional design method significantly depends on the designer’s experience, which uses equivalent magnetic circuit models, and therefore the SRM design is not well developed. A novel SRM electromagnetic design and optimization method is developed, which uses the current-fed FEA simulation as the SRM performance estimation tool. This method serves as the main innovation of this research work. First, the proposed method is applicable to any SRM topologies and dimension, and no detailed modeling of a specific SRM configuration is required in advance. Therefore, an automated SRM design and optimization approach is developed. Secondly, great accuracy of the SRM electromagnetic analysis, e.g. flux density, torque, and current calculation, is achieved by using FEA simulation instead of simplified magnetic circuit approximations. This contribution is particularly significant when considering the poor accuracy of conventional SRM analytical analysis methods, where several assumptions and approximations are used. Lastly, the proposed design method takes the typical SRM control strategy into account, where the excitation current profile is characterized as a trapezoid. This method adapts the flux linkage of the first FEA simulation result to specify the excitation current profile for the second FEA simulation, so the calculated SRM performance in FEA simulation agrees with the measurement on a practical machine. The proposed SRM design and optimization method is used for a 12/8 SRM rotor design and for a complete 4/2 SRM design. These design examples validate the applicability of the proposed method to different SRM configurations and dimensions. Detailed design steps are presented for both design cases, and the selection of the parametric design variables are also discussed. The optimization results are demonstrated using multi-dimension diagrams, where the optimal design with the highest torque can be easily identified. The FEA simulation results are compared to the experimental results of a fabricated SRM prototype, and good agreement is found. In addition, a new rotor configuration with a flux bridge is proposed for an ultra high speed SRM design. The primary motivation of this rotor topology is to reduce the windgae losses and the acoustic noise at a high speed of 50,000 rpm. However, care must be taken for the flux bridge design, and the impact of different flux bridge thicknesses to the SRM performance is studied. Meanwhile, the manufacturing difficulties and the mechanical stresses should also be considered when fabricating the flux-bridge rotor. As a result, two SRM prototypes are built, and the two rotors are one without a flux bridge and one with a flux bridge. The prototypes are tested at different speeds (10,000 rpm, 20,000 rpm and 50,000 rpm) respectively, and the experimental results show good agreement with the FEA simulation results.

Στην παρούσα διπλωματική εργασία γίνεται περιγραφή του ηλεκτρικού κινητήριου συστήματος της Πατραϊκής Χαρτοποιίας αποτελούμενο από κινητήρες συνεχούς ρεύματος για την παραγωγή χαρτιού "tissue". Επίσης παρουσιάζεται η σχεδίαση συστήματος καταγραφής βλαβών σε περιστρεφόμενες μηχανές μέσω της ανάλυσης φάσματος κραδασμών στο πλαίσιο της εφαρμοσμένης μεθόδου παρακολούθησης κραδασμών της προβλεπτικής συντήρησης. / In the current diploma thesis takes place a description of the electric motor drive system of Patraikh Xartopoiia which consist of direct current machines for the production of tissue type paper. Furthermore the design of damage recording system in rotating motors through vibration analysis is presented in the line of vibration monitoring applied method.

In this study, a three-axes PC numerical control system for industrial applications has been developed. With this system, fast and cheap prototyping of designed objects can be realized. The system consists of software and a hardware which includes an XYZ positioning table and three step motors controlling this table. A proper drive circuit for the stepper motors is utilized. The software digitizes two dimensional drawings of three dimensional objects and generates the control signals for the XYZ positioning table. The software is developed under Microsoft Studio Visual Basic 6.0 environment regardless of the OS of the PC. The parallel port of the PC has been utilized for generating the necessary control signals for the stepper motors.

High dynamic performance, which is obtained from dc motors, became achievable from induction motors with the recent advances in power semiconductors, digital signal processors and development in control techniques. By using field oriented control, torque and flux of the induction motors can be controlled independently as in dc motors. The control performance of field oriented induction motor drive greatly depends on the correct stator flux estimation. In this thesis voltage model is used for the flux estimation. Stator winding resistance is used in the voltage model. Also leakage inductance, mutual inductance and referred rotor resistance values are used in vector control calculations. Motor control algorithms use motor models, which depend on motor parameters, so motor parameters should be measured accurately. Induction motor parameters may be measured by conventional no load and locked rotor test. However, an intelligent induction motor drive should be capable of identifying motor parameters itself. In this study parameter estimation algorithms are implemented and motor parameters are calculated. Then these parameters are used and rotor flux oriented vector control is implemented. Test results are presented.

Fault tolerant motor drives are becoming more important in safety critical applications. Although a single motor module fault tolerant drive may be sufficient in some applications, this motor drive only offers limited redundancy. This thesis investigated the dual motor module fault tolerant drive system in which two motor modules were connected electrically in phase and on a common shaft provide redundancy and to increase the reliability of the entire drive system. A general phase current mathematical model to produce the desired output torque was developed to minimize copper loss and torque ripple in the motor drive, which is applicable to both sinusoidal and trapezoidal brushless permanent magnet motor types. A detailed fault effect investigation was performed in this thesis and it is concluded that switch short-circuit fault is the most serious fault since it reduces the electromagnetic torque output significantly and generates larger torque ripple in the motor drive due to the presence of large drag torque. Three fault remedial strategies were proposed to compensate the torque loss and to reduce the torque ripple under different faulty conditions. It is concluded from the analytical results that fault remedial strategy 3 is the tradeoff algorithm in which the zero torque ripple factor can be achieved with only a modest increase in copper loss comparing with the minimum possible value. Two practical dual motor module fault tolerant brushless permanent magnet drive test arrangements with different motor structures were developed in this thesis. The computer simulation studies using the MATLAB Simulink were performed to verify the effectiveness of the proposed fault remedial strategies. The efficiency of the motor drive was predicted based on torque loss measurements and the results were verified in the simulation study. The effect of faults on the drive efficiency was investigated as well. The entire fault tolerant motor drive control system was also developed to verify the analytical and simulation results. A fault detection and identification method to detect switch open-circuit faults, switch short-circuit faults, and the winding short-circuit faults was also proposed. Its advantages are the simplicity of the implementation and reduction of the cost of the drive system. The experimental results demonstrated that the proposed fault remedial strategies can be implemented in real time motor control and are effective to compensate the torque loss and reduce the torque ripple. / Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 2008