Despite its simple construction, robustness and low manufacturing cost, the application areas of SR motors are remained limited due to the high level of acoustic noise and torque ripple. In this thesis work, two different type of controllers are designed and implemented in order to minimize the acoustic noise and torque ripple which are considered as the major problems of SR motors. In this scope, first the possible acoustic noise sources are investigated. A sliding mode controller is designed and implemented to reduce the shaft torque ripple which is considered as a major source of acoustic noise. The performance of the controller is experimentally tested and it is observed that especially in low speed region reduction of torque ripple is significant. The torque ripple minimization performance of the controller is also tested at different speeds and the acoustic noise levels are recorded simultaneously. Comparing the noise mitigation with the noise reduction the correlation between the acoustic noise and shaft torque ripple is investigated. The results obtained from this investigation indicated that the torque ripple is not a major source of acoustic noise in SR motors. After this finding, radial force which is the other possible acoustic noise source of SRM is taken into consideration. The effects of control parameters on radial force and the motor efficiency are investigated via simulations. With the intuition obtained from this analysis, a switching angle neuro-controller is designed to minimize the peak level of radial forces. The performance of the mentioned controller is verified through noise records under steady state conditions. Regarding to the radial force simulations and the acoustic noise measurements, it is deduced that the radial force is the major source of acoustic noise. On the other hand, another controller is designed and implemented which increases the average torque per ampere value in order to increase the efficiency of the motor. It is seen that this controller has a good effect on increasing the efficiency but does not guarantee to operate at maximum efficiency.

Made available in DSpace on 2016-12-12T17:38:35Z (GMT). No. of bitstreams: 1 Maria Bernardete da Silva.pdf: 1124461 bytes, checksum: af908c9af2f2467bc1dc36b3d17d4585 (MD5) Previous issue date: 2006-12-11 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The torque ripple in electric motors affects the performance of devices and machines which need precision in its control. Due to the undesirable effect of the ripple torque it has had recently an effort in the direction to get minimization strategies which permit the reduction or even elimination of this kind of torque. The goal of this work is the study and comparison between two minimization strategies of the ripple torque in hybrid step motor and apply that strategies in digital control. A step motor´s description is supplied together with other kinds of torque belong to this motors. The mathematical model for the step motor is described and based on this model has got the ripple torque´s equation which will be used in the formulation of the torque ripple minimization. To each strategy is presented a detailed mathematical foundation to the reader to be clear the development to each strategy. The first strategy presents a ripple torque´s model by hybrid step motors linearization that after linearized may be used standard methods of digital control design. The second uses an adaptative linearization to improve the hybrid step motor´s performance with low cost. By the end, a comparison between two strategies is made giving to the reader the advantages and disadvantages of each strategy. / O conjugado de ondulação em motores elétricos afeta o desempenho de máquinas e dispositivos que exijam precisão no seu controle. Devido aos efeitos indesejáveis do conjugado de ondulação tem havido recentemente um esforço no sentido de se obter estratégias de minimização que tornem possíveis a redução ou até mesmo a eliminação desse tipo de conjugado. O objetivo deste trabalho é o estudo e a comparação de duas estratégias de minimização do conjugado de ondulação em motores de passo híbrido onde as duas estratégias analisadas são aplicadas em controle digital. Uma descrição dos motores de passo é fornecida juntamente com os diversos tipos de conjugado existentes nesses tipos de motores. Um modelo matemático para o motor de passo é descrito e a partir desse modelo é obtida a equação do conjugado de ondulação que será usada na formulação dos problemas de minimização do conjugado de ondulação. Para cada uma das estratégias é apresentada em detalhes a fundamentação matemática para que o leitor tenha um claro entendimento do desenvolvimento de cada uma das estratégias. A primeira estratégia apresenta um modelo de máquina que representa as ondulações de conjugados pela linearização de motores de passo híbridos que, após linearizado permite o emprego de métodos padrões de projeto de controle digital. A segunda utiliza a linearização adaptativa para melhorar a performace do motor de passo híbrido com baixo custo. Por fim, é feita uma comparação entre as duas estratégia, apresentando-se ao leitor as vantagens e desvantagens de cada uma delas.

Synchronous generators have been used in hydropower from more than a century where, traditionally, the field current is transferred to the rotor using slip rings and carbon brushes. There are some major disadvantages following the use static excitation; regular and expensive maintenance, as well as a source of carbon dust which, due to buildup, may cause short circuits. To avoid these problems associated with slip ring exciter systems, a system that use induction to transfer power to the rotor could be used instead. Systems that utilize brushless excitation today usually regulates the current by controlling the magnetization of the exciter stator, which is comparably slower than their static counterparts. In order to allow for swift regulation of the field current from a brushless exciter, required power electronics and controllers have to be present on the rotor shaft instead. The aim of this project is to start investigating if commercially available products, which are originally indented to be used in a stationary environment, could accomplish this. The results from this study shows that it is possible to use such products to control the field current. The components were found to withstand the exposure of high g-forces and vibrations, albeit only during the relatively small amount of time in which rotary testing was performed. As such there is no certainty that the components would remain functional for the considerably longer time that any commercial use would require them to.

No description available.

Voltage source inverter (VSI) is used to control the speed of an induction motor by applying AC voltage of variable amplitude and frequency. The semiconductor switches in a VSI are turned on and off in an appropriate fashion to vary the output voltage of the VSI. Various pulse width modulation (PWM) methods are available to generate the gating signals for the switches. The process of PWM ensures proper fundamental voltage, but introduces harmonics at the output of the VSI. Ripple in the developed torque of the induction motor, also known as pulsating torque, is a prominent consequence of the harmonic content. The harmonic voltages, impressed by the VSI on the motor, differ from one PWM method to another. Space-vector-based approach to PWM facilitates a large number of switching patterns or switching sequences to operate the switches in a VSI. The switching sequences can be classified as conventional, bus-clamping and advanced bus-clamping sequences. The conventional sequence switches each phase once in a half-carrier cycle or sub-cycle, as in case of sine-triangle PWM, third harmonic injection PWM and conventional space vector PWM (CSVPWM). The bus-clamping sequences clamp a phase to one of the DC terminals of the VSI in certain regions of the fundamental cycle; these are employed by discontinuous PWM (DPWM) methods. Popular DPWM methods include 30 degree clamp PWM, wherein a phase is clamped during the middle 30 degree duration of each quarter cycle, and 60 degree clamp PWM which clamps a phase in the middle 60 degree duration of each half cycle. Advanced bus-clamping PWM (ABCPWM) involves switching sequences that switch a phase twice in a sub-cycle besides clamping another phase. Unlike CSVPWM and BCPWM, the PWM waveforms corresponding to ABCPWM methods cannot be generated by comparison of three modulating signals against a common carrier. The process of modulation in ABCPWM is analyzed from a per-phase perspective, and a computationally efficient methodology to realize the sequences is derived. This methodology simplifies simulation and digital implementation of ABCPWM techniques. Further, a quick-simulation tool is developed to simulate motor drives, operated with a wide range of PWM methods. This tool is used for validation of various analytical results before experimental investigations. The switching sequences differ in terms of the harmonic voltages applied on the machine. The harmonic currents and, in turn, the torque ripple are different for different switching sequences. Analytical expression for the instantaneous torque ripple is derived for the various switching sequences. These analytical expressions are used to predict the torque ripple, corresponding to different switching sequences, at various operating conditions. These are verified through numerical simulations and experiments. Further, the spectral properties are studied for the torque ripple waveforms, pertaining to conventional space vector PWM (CSVPWM), 30 degree clamp PWM, 60 degree clamp PWM and ABCPWM methods. Based on analytical, simulation and experimental results, the magnitude of the dominant torque harmonic with an ABCPWM method is shown to be significantly lower than that with CSVPWM. Also, this ABCPWM method results in lower RMS torque ripple than the BCPWM methods at any speed and CSVPWM at high speeds of the motor. Design of hybrid PWM methods to reduce the RMS torque ripple is described. A hybrid PWM method to reduce the RMS torque ripple is proposed. The proposed method results in a dominant torque harmonic of magnitude lower than those due to CSVPWM and ABCPWM. The peak-to-peak torque in each sub-cycle is analyzed for different switching sequences. Another hybrid PWM is proposed to reduce the peak-to-peak torque ripple in each sub-cycle. Both the proposed hybrid PWM methods reduce the torque ripple, without increasing the total harmonic distortion (THD) in line current, compared to CSVPWM. CSVPWM divides the zero vector time equally between the two zero states of a VSI. The zero vector time can optimally be divided to minimize the RMS torque ripple in each sub-cycle. It is shown that such an optimal division of zero vector time is the same as addition of third harmonic of magnitude 0.25 times the fundamental magnitude to the three-phase sinusoidal modulating signals. ABCPWM applies an active state twice in a sub-cycle, with the active vector time divided equally. Optimal division of active vector time in ABCPWM to minimize the RMS torque ripple is evaluated, both theoretically and experimentally. Compared to CSVPWM, this optimal PWM is shown to reduce the RMS torque ripple significantly over a wide range of speed. The various PWM schemes are implemented on ALTERA CycloneII field programmable gate array (FPGA)-based digital control platform along with sensorless vector control and torque estimation algorithms. The controller generates the gating signals for a 10kVA IGBT-based two-level VSI connected to a 5hp, 400V, 4-pole, 50Hz squirrel-cage induction motor. The induction motor is coupled to a 230V, 3kW separately-excited DC generator.

No description available.

The Permanent Magnet Synchronous Motors (PMSM) have wide application in the robotics field due to its efficiency and reliability. As a servo system, it demands high precision in different control applications. Torque ripple is a critical issue resulting in mechanical vibrations and shortening the life of PMSMs, especially at low speeds. Because the magnitude of speed harmonics is proportional to the magnitude of the torque harmonics of the same order, methods to reduce speed harmonics can be utilized for torque ripple minimization. This thesis work proposes three methods for torque ripple reduction. One method is based on harmonic speed control (HSC) and harmonic current control (HCC). Another method uses the fuzzy to adjust PI parameters based on HSC-HCC. The third method utilizes torque ripple estimation (TRE) and HCC. In the proposed methods, torque ripples are estimated using a torque ripple model (TRM). At low speeds, speed harmonics and current harmonics are obtained based on an adaptive linear neural-based filter. The errors between the optimal harmonic current reference from HSC or TRE and the harmonic current from extraction are used to generate harmonic voltage in HCC. This harmonic voltage is fed back to compensate and reduce torque ripple. Furthermore, a feedforward compensation method is proposed to minimize torque ripple across a range of speeds based on the feedback compensation results. Finally, simulations and experiments are carried out to demonstrate the validity and performance of the proposed torque ripple reduction methods.

L'objectif principal de nos travaux consiste à développer des méthodes d’optimisation des performances de la MSRV sur le plan de la conception et de la commande. La première partie est consacrée à la commande de la MSRV avec prise en compte de la saturation, de l'effet croisé et des pertes-fer. Deux stratégies de commande permettant d’améliorer les performances de la machine en régime permanent sont présentées: commande à rendement optimal et commande à couple maximum par ampère. La deuxième partie de ce travail porte sur la commande de la MSRV en vue de réduire les ondulations de couple. L’optimisation des courants statoriques a été obtenue selon deux critères : un couple électromagnétique constant et des pertes par effet Joule minimales. Une formule originale a été présentée dans le cas où le courant homopolaire est pris en compte. Des schémas de commande neuronale en couple et en vitesse sont ensuite proposés. L’apprentissage, réalisé en ligne, fait que cette proposition est tout à fait adaptée aux applications en temps réel. La troisième partie traite de la conception au moyen de la méthode de calcul numérique par élément finis. Grâce au logiciel JMAG, les barrières du flux au rotor de la MSRV ont été optimisées permettant d’augmenter le couple moyen, le facteur de puissance et le rendement de la machine. Enfin, toutes les approches neuromimétiques ont été validées par de tests expérimentaux. De plus, des comparaisons avec les méthodes de commande classique démontrent la validité des méthodes proposées. / The main objective of our work is to develop the methods for performance optimization of the SynRM in terms of the design and control. The first part is devoted to control of the SynRM taking into account the saturation, cross coupling and iron losses. Two strategies control to improve the performances of the machine in steady-state are presented: optimal efficiency control and maximum torque per ampere control. The second part of this work focuses on the control of the non-sinusoidal SynRM to reduce torque ripple. Optimal stator currents were obtained with the objectives: a constant electromagnetic torque and minimum ohmic losses. An original formula was presented in the case where the homopolar current is considered. The torque and speed control based on artificial neural networks are then proposed to obtain optimal currents online in real time. The third part deals with the design optimization of SynRM by finite element method. With JMAG software, the barriers of the rotor SynRM were optimized to maximize the average torque, power factor and efficiency of the machine. Finally, all the approaches based on neural networks have been validated by experimental tests. Moreover, the comparisons with conventional methods demonstrate the validity of the proposed methods.

In this thesis, a new Poly Phase Motor (rotary actuator) based on the Shape Memory Alloy (SMA) is presented. Details of Design, Modeling, Characterization, Realization and Control of Poly Phase SMA Motor are presented. Motor with 3 and 6 Phases, with appropriate Control circuit have been realized in laboratory and simulated results have been verified experimentally. In literature, broadly two types of Shape Memory Alloy based motors namely limited rotation motor and unlimited rotation motor are found. In the unlimited rotation type SMA based motor the SMA element is in the spring form. Hence, an attempt has been made in this research to develop an Unlimited Rotating type Balanced Poly Phase Motor based on SMA wire in series with a spring in each phase. By isolating SMA actuation and spring action a constant force by the SMA wire through out its range of operation is achieved. While designing the motor, similarity in function between Poly Phase SMA Motor and Stepper Motor was found. Hence, the Poly Phase Motor is characterized similar to that of a Stepper Motor. Functionally, the Poly Phase Motor can be used in stepping mode for generating incremental motion and servo mode for generating continuous motion. Various parameters of the motor have been defined. The motor can be actuated in either direction with different Phase sequencing methods, which are presented in this work. While explaining sequencing methods, effect of the thermal time constants has also been presented. The lumped thermal model is used for dynamic simulation of motor. The motor has been modeled with a new approach to the SMA wire Hysteresis model. This model is simple and useful for real time control applications. Model is implemented using Simulink and used for the simulation of the motor. Generalization of the motor concept is done and motor up to 16 Phases are studied and the simulation results done using MATLAB are discussed. It could be observed that the torque generated by the motor increases with increased number of phases while the torque ripple reduces. The motor torque ripple is better for motor with odd number of phases due to its construction. Two methods of achieving servo motion are presented. The first method is Micro Stepping, consisting of controlling single phase temperature with a position feedback. The second method is Antagonistic Control of temperatures of phases with position feedback. Both the above methods use PID Controller with optical encoder feedback for position sensing. Performance of the actuator with step, ramp and triangle inputs has been simulated using Simulink and verified experimentally for various loads and disturbances. Positional accuracy of 0.07% for the Step input and for the full rotation of 3600 is achieved. Vector Control of SMA Motor is presented. By this method Speed and the torque of the motor will be effectively controlled. Since the temperatures of the wires are controlled in this research, this method is named as Thermal Space Phasor or Vector Based Control. This method of rotation of motor is simulated using Simulink and verified experimentally. Here the current through the SMA is controlled so as to get near sinusoidal variation in temperature. This leads to a near Sinusoidal variation of force. It is shown that by controlling the temperature of phases Sinusoidally with a phase shift of 1200, the Resultant Force will be a constant over the Spatial angle of 3600 and its Velocity of rotation will be Constant. Open loop and closed loop control of the speed and torque is presented. While the motor rotates at fixed Speed and Torque in Open Loop Control, motor adopts to change in torque and velocity in Closed Loop control with reduced ripple. PID Controller is used for closed loop control. The presented rotary actuator and their experimental results set a new standard for SMA based new generation rotary actuators and control.

Induction motor (IM) drives are employed in a wide range of industries due to low maintenance, improved efficiency and low emissions. Industrial installations of high-power IM drives rated up to 30 MW have been reported. The IM drives are also employed in ultra high-speed applications with shaft speeds as high as 500; 000 rpm. Certain applications of IM drives such as gas compressors demand high power at high speeds (e.g. 10 MW at 20; 000 rpm). In high-power voltage source inverter (VSI) fed induction motor drives, the semiconductor devices experience high switching energy losses during switching transitions. Hence, the switching frequency is kept low in such high-power drives. In high-speed drives, the maximum modulation frequency is quite high. Hence, at high speeds and/or high power levels, the ratio of switching frequency to fundamental frequency (i.e. pulse number, P ) of the motor drive is quite low. Induction motor drives, operating at low-pulse numbers, have significant low-order volt-age harmonics in the output. These low-order voltage harmonics are not filtered adequately by the motor inductance, leading to high total harmonic distortion (THD) in the line current as well as low-order harmonic torques. The low-order harmonic torques may lead to severe torsional vibrations which may eventually damage the motor shaft. This thesis addresses numerous issues related to low-pulse-number operation of VSI fed IM drives. In particular, optimal pulse width modulation (PWM) schemes for minimization of line current distortion and those for minimization of a set of low-order harmonic torques are proposed for two-level and three-level inverter fed IM drives. Analytical evaluation of current ripple and torque ripple is well established for the induction motor drives operating at high pulse numbers. However, certain important assumptions made in this regard are not valid when the pulse number is low. An analytical method is proposed here for evaluation of current ripple and torque ripple in low-pulse-number induction motor drives. The current and torque harmonic spectra can also be predicted using the proposed method. The analytical predictions of the proposed method are validated through simulations and experimental results on a 3:7-kW induction motor drive, operated at low pulse numbers. The waveform symmetries, namely, half-wave symmetry (HWS), quarter-wave symmetry (QWS) and three-phase symmetry (TPS), are usually maintained in induction motor drives, operating at low switching frequencies. Lack of HWS is well known to introduce even harmonics in the line current. Impact of three-phase symmetry on line current and torque harmonic spectra is analyzed in this thesis. When the TPS is preserved, there are no triplen frequency components in the line current and also no harmonic torques other than those of order 6, 12, 18 etc. While TPS ensures that the triplen harmonics in the three-phase pole voltages are in phase, these triplen frequency harmonics form balanced sets of three-phase voltages when TPS is not preserved. Hence, triplen frequency currents flow through the stator windings. These result in torque harmonics of order 2, 4, 6, 8, 10 etc., and not just integral multiples of 6. These findings are well supported by simulation and experimental results. One can see that two types of pole voltage waveforms are possible, when all waveform symmetries (i.e. HWS, TPS and QWS) are preserved in a two-level inverter, These are termed as type-A and type-B waveforms here. Also, QWS could be relaxed, while maintain-ing HWS and TPS, leading to yet another type of pole voltage waveform. Optimal switching angles to minimize line current THD are reported for all three types of pole voltage wave-forms. Theoretical and experimental results on a 3:7-kW IM drive show that optimal type-A PWM and optimal type-B PWM are better than each other in different ranges of modulation at any given low pulse number. In terms of current THD, the optimal PWM without QWS is found to be close to the better one between optimal type-A and optimal type-B at any modulation index for a given P . A combined optimal PWM to minimize THD is proposed, which utilizes the superior one between optimal type-A and optimal type-B at any given modulation index and pulse number. The performance of combined optimal PWM is shown to be better than those of synchronous sine-triangle (ST) PWM and selective harmonic elimination (SHE) PWM through simulations and experiments over a wide range of speed. A frequency domain (FD) based and another synchronous reference frame (SRF) based optimal PWM techniques are proposed to minimize low-order harmonic torques. The objective here is to minimize the combined value of low-order harmonic torques of order 6, 12, 18, ..., 6(N 1), where N is the number of switching angles per quarter cycle. The FD based optimal PWM is independent of load and machine parameters while the SRF based method considers both load and machine parameters. The offline calculations are much simpler in case of FD based optimal PWM than in case of SRF based optimal PWM. The performance of the two schemes are comparable and are much superior to those of synchronous ST PWM and SHE PWM in terms of low-order harmonic torques as shown by the simulation and experimental results presented over a wide range of fundamental frequency, The proposed optimal PWM methods for two level-inverter fed motor drives to minimize the line current distortion and low-order torque harmonics, are extended to neutral point clamped (NPC) three-level inverter fed drive. The proposed optimal PWM methods for the NPC inverter are compared with ST PWM and SHE PWM, having the same number of switching angles per quarter. Simulation and experimental results on a 3:7-kW induction motor drive demonstrate the superior performance of proposed optimal PWM schemes over ST PWM and SHE PWM schemes. The di_erent optimal PWM schemes proposed for two-level and three-level inverter fed drives, having di_erent objective functions and constraints, are all analyzed from a space vector perspective. The three-phase PWM waveforms are seen as a sequence of voltage vector applied in each case. The space vector analysis leads to determination of optimal vector sequences, fast o_ine calculation of optimal switching angles and e_cient digital implementation of the proposed optimal PWM schemes. A hybrid PWM scheme is proposed for two-level inverter fed IM drive, having a maximum switching frequency of 250 Hz. The proposed hybrid PWM utilizes ST PWM at a _xed frequency of 250 Hz at low speeds. This method employs the optimal vector sequence to minimize the current THD at any speed in the medium and high speed ranges. The proposed method is shown to reduce both THD as well as machine losses signi_cantly, over a wide range of speed, compared to ST PWM Position sensorless vector control of IM drive also becomes challenging when the ratio of inverter switching frequency to maximum modulation frequency is low. An improved procedure to design current controllers, and a closed-loop ux estimator are reviewed. These are utilized to design and implement successfully a position sensorless vector controlled IM drive, modulated with asynchronous third harmonic injected (THI) PWM at a constant switching frequency of 500 Hz. Sensorless vector control is also implemented successfully, when the inverter is modulated with synchronized THI PWM and the maximum switching frequency is limited to 500 Hz.