Dissertations / Theses on the topic 'Electric motors, Direct current - Electric motors, Direct current'

Permanent magnet brushless DC motors that have found wide application in high performance servo drives need absolute rotor position sensors. However, the cost of the position sensor limits the use of brush less DC motors for low performance applications such as automotive and home appliances. A sensorless starting scheme for brushless DC motors is studied in this thesis. A hardware implementation of the starting scheme has been instrumented. The modeling and simulation of the sensorless starting performance of brushless DC motors have been accomplished to gain the insight into the process. The experimental results confirm the theoretical prediction that the permanent magnet brush less DC motor can be started without a position sensor. The experimental setup with individual subsystems are described in detail.

Master of Science

Several new nonlinear algorithms for speed control of electrical drives are developed. They are compared with the algorithms for integral-proportional (I-P) control, sliding mode control (SLM) and adaptive control which uses the torque and parameter observer. To achieve fast and robust response, all algorithms use very large gains. In a new, variable limit PI (VLPI) control algorithm, integrator windup is completely prevented by using a high gain, "variable dead zone" nonlinearity as a local feedback over the integrator. Recently proposed soft variable structure (SVS) control, derived by using the Liapunov direct method, is modified so that the algorithm can be implemented with only the output measurements. Proper operation is achieved for any value of the output variable. The new control is very robust, but exhibits a steady state error. Two versions of the adaptive PI (API) control algorithm are developed that have fast and robust transient response with zero steady state error. The SVS API version operates similarly as the modified SVS control, but does not have its drawbacks. The SLM API version operates like the SLM control during large transients, and like VLPI control when close to the steady state. The local stability of the control is proved using the "small gain theorem". Its global behavior is analyzed by describing functions. Very good operation of the SVS API speed control within the proportional position loop is demonstrated. Faster transient response is achieved by implementing the SLM adaptive proportional control in the position loop. The operation is the same as the operation of the SLM API control in the speed loop. Similarity between modified SVS control, and classical adaptive algorithms is shown. API control, All the algorithms are simulated and compared for twofold and tenfold changes in plant parameters. The experimental verification of the results for I-P control, SLM control, and modified SVS control, are presented. Theory of the new algorithms is general, such that the results are applicable to any SISO plant that can be stabilized.
Ph. D.

Thesis (M.S.)--University of Missouri--Rolla, 2007.
Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed October 25, 2007) Includes bibliographical references (p. 61-62).

Brushless Direct Current (BLDC) motors are one of the motor types rapidly gaining popularity. BLDC motors are being increasingly used in critical high performance industries such as appliances, automotive, aerospace, consumer, medical, industrial automation equipment and instrumentation. Fault detection and condition monitoring of BLDC machines is therefore assuming a new importance. The objective of this research is to advance the field of rotor and load fault diagnosis in BLDC machines operating in a variety of operating conditions ranging from constant speed to continuous transient operation. This objective is addressed as three parts in this research. The first part experimentally characterizes the effects of rotor faults in the stator current and voltage of the BLDC motor. This helps in better understanding the behavior of rotor defects in BLDC motors. The second part develops methods to detect faults in loads coupled to BLDC motors by monitoring the stator current. As most BLDC applications involve non-stationary operating conditions, the diagnosis of rotor faults in non-stationary conditions forms the third and most important part of this research. Several signal processing techniques are reviewed to analyze non-stationary signals. Three new algorithms are proposed that can track and detect rotor faults in non-stationary or transient current signals.

Submitted to the Department of Electrical Engineering in Fulfilment of the Requirements for the Magister Technologiae in Electrical Engineering at the Cape Peninsula University of Technology SUPERVISOR: E. VOSS NOVEMBER 2013
The reluctance synchronous machine (RSM) operates on the principle of magnetic reluctance, which is produced through a careful selection of rotor flux barriers and cut-outs. Magnetic reluctivity is the resistance to magnetic flux and can be directly related to the principles of Ohm’s law in electrical circuits. Although reluctance motors have been known for more than 150 years, researchers lost interest when Nikola Tesla’s induction machine (IM) was introduced to industry. Over the last few decades, however, RSMs have shown a lot of potential. They are cheap, robust, reliable, and their rotors can also be used in the stators of IMs. The disadvantage of these machines is an inherently high torque ripple, being the result of its rotor geometry, but the biggest advantage is having a significant reduction in copper losses after the rotor cage has been removed. This advantage drove engineers to investigate, optimise and modify the performance and structure of this machine, which led to the usage of electronic drive systems. The recent advances in technology have allowed researchers to further investigate and modify the design and performance of this special type of machine, with the integration of Finite Element Analysis (FEA) software also making a contribution to the development of the RSM’s current driven systems. The voltage-fed RSM, driven direct-on-line (DOL) from the utility supply, was left in the shadows as the current-fed RSM took reign, but still is, in the author’s opinion, not yet fully analysed. This thesis practically investigates the performance characteristics of the cageless, voltage-fed 3kW RSM in its steady-state operation, under various loads. These performance characteristics are also compared to a RSM driven from a sensorless vector drive (current-fed) to investigate the advantages and disadvantages between the two. Experiments performed on the test bench immediately reveal a limitation to the voltage-fed RSM’s ability to drive higher loads. While the current-fed RSM conveniently reaches 150% of its full-load, the voltage-fed RSM, due to its cageless structure, only reaches 110% of its full-load power. Despite this discovery, the voltage-fed RSM proves to have a lower core loss, harmonic content and torque ripple. Using a FE software package with an integrated source-code, additional parameters such as the dq-axis inductances and currents are also compared and analysed in terms of its reaction to an increase in load. The eddy-current, hysteresis and excess losses are also analysed as well as the harmonic components caused by the geometry of the RSM. For academic purposes, a fair amount of emphasis is placed on the approach to the problem. The preparation for the FE simulation is explained in detail, providing insight into the FE mathematical model as well as parameter acquisition. These parameters include current angle, friction and windage losses, stator resistance, end-winding leakage reactance, core loss and inertia. The results obtained by the FE model are compared to that of the measured results and is found to have an error of only 0.52%. Furthermore, this study attempts to find the feasibility of the voltage-fed RSM’s practicality in modern-day industry. The conclusion is drawn that the voltage-fed RSM could be used as a more elegant alternative to an otherwise over-complicated and over-priced installation.

This thesis describes the design and implementation of a simple variable speed drive (VSD) based on a brushless direct current (BLDC) machine and discrete logic circuits. A practical VSD was built, capable of operating a BLDC machine in two quadrants, motoring and regenerative braking. The intended applications are electric scooters and electric bicycles, where the recovered energy from braking extends the range of the vehicle. A conceptual four quadrant VSD, suitable for three and four wheelers requiring reverse operation, was designed and tested in simulation. Simplicity was emphasized in this design to help achieve a robust, easy to analyse system. The versatility of multi-function gate integrated circuits (ICs) made them ideal for implementing the commutation logic and keeping the system simple. The BLDC machine has sensors with a resolution of 60 ed to determine rotor position. An electronic commutator or phase switcher module interprets the position signals and produces a switching pattern. This effectively transforms the BLDC machine into a direct current (DC) brushed machine. A synchronous step down converter controls the BLDC machine current with a tolerance band scheme. This module treats the BLDC machine as if it was a DC machine. The leakage inductance of the electric machine is used as the inductive filter element. The unipolar switching scheme used ensures that current flows out of the battery only for motoring operation and into the battery only during regeneration. The current and torque are directly related in a DC brushed machine. The action of an electronic commutator or phase switcher creates that same relationship between torque and current in a BLDC machine. Torque control is achieved in the BLDC machine using a single channel current controller. The phase switcher current is monitored and used to control the duty ratio of the synchronous converter switches. Successful operation of the practical VSD was achieved in two quadrants: forwards motoring and forwards regenerating. The maximum tested power outputs were 236W in motoring mode and 158W in regenerating mode. The output torque could be smoothly controlled from a positive to a negative value. iv v Simulation of the conceptual four quadrant design was successful in all the motoring, generating and active braking zones. The required manipulation of logic signals to achieve this type of operation was done automatically while the machine was running. The resulting output torque is smoothly controlled in all of the operating zones. Commutation at certain speeds and torques are handled better by some topologies than others. Some current sensing strategies adversely affect instantaneous phase currents under certain conditions. The final design chose the method where phase currents experience no overshoot, minimizing component stress. The battery, or energy storage system, used in verifying the operation of the VSD in the practical electric bicycle was found to be the most limiting component. In regenerating mode, the low charge acceptance rate of the battery reduced the maximum retarding torque and energy recovery rate.

This bachelor’s thesis aims to show an extensive overview of all the parts that build up an electric load driven longboard and see if a load controlled longboard can be seen as a safe, comfortable and convenient alternative to the more common remote controlled longboard. The thesis will also answer how weight can be measured on a longboard in the most effective way, what the most comfortable riding technique is and what a good motor-battery configuration to be able to travel at 30 km/h and 10 km would be. The longboard measures the weight distribution with load cells located between the deck and the trucks. An Arduino translates the input from the load cells to a certain speed and then sends it to an ODrive which controls a BLDC motor that is powered by two LiPo batteries. The results show that a load controlled longboard can very well be seen as a good alternative if right riding technique is used. The best technique is when the longboard accelerates when the rider tilts and keeps a constant speed when the rider stands straight. The best way to measure the weight is to fasten the trucks with hinges which lets the load cells register weight without anything interfering. Not all tests could be done because of Covid-19 but a measured top speed of 15 km/h with a high gear ratio is a promising result for the future when more suitable gear ratios will be tested to try to reach the goal of 30 km/h.
Det här kandidatexamensarbetet strävar efter att visa en omfattande överblick på alla delar som bygger upp en elektrisk lastdriven longboard och se om en laststyrd longboard kan ses som ett säkert, komfortabelt och behändigt alternativ till den vanligare radiostyrda longboarden via handkontroll. Det här arbetet kommer också svara på hur vikt kan mätas på en longboard på ett så effektivt sätt som möjligt, vad som är den mest bekväma åkstilen och vad är en bra motor-batteri konfiguration för att kunna åka i 30 km/h och nå 10 km skulle vara. Longboarden mäter viktfördelningen med lastceller som är placerade mellan brädan och truckarna. En Arduino omvandlar indatan från lastcellerna till en specifik hastighet som den sedan skickar till en ODrive som kontrollerar en borstlös likströmsmotor som i sin tur är driven av två LiPo batterier. Resultaten visar att en laststyrd longboard kan mycket väl ses som ett bra alternativ om rätt åkstil används. Den bästa stilen är att longboarden accelererar när åkaren lutar sig och håller en konstant hastighet när åkaren står rakt. Det bästa sättet att mäta vikt är att montera truckarna på gångjärn som låter lastcellerna mäta vikt utan att något stör. Alla tester kunde inte utföras på grund av Covid-19 men en uppmätt topphastighet på 15 km/h med en hög utväxling är ett lovande resultat för framtiden när lämpligare utväxlingar kommer testas för att försöka nå målet på 30 km/h.

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CNPQ
Vários estudos têm sugerido que o cerebelo tem um papel crucial no aprendizado motor. Pesquisas sobre o efeito da estimulação cerebelar na excitabilidade cortical vêm sendo desenvolvidas, porém, a influência da polaridade da estimulação, assim como a lateralidade dos efeitos não são bem esclarecidos. Outra lacuna é o efeito da estimulação sobre funções motoras não específicas, como o aprendizado motor medido através do tempo de reação serial (TRS), e tarefas motoras complexas, como o teste de escrita, podendo ter estes teste resultados divergentes devido a diferentes mecanismos responsáveis por sua execução. Portanto, a presente dissertação é composta de dois estudos. O primeiro estudo teve como objetivo investigar os efeitos da estimulação transcraniana por corrente contínua cerebelar (ETCCc) sobre a excitabilidade do córtex motor primário ipsilateral e o aprendizado motor realizado com o membro superior contralateral em indivíduos saudáveis. Nele foram analisados os efeitos polaridade-dependente da ETCCc sobre o aprendizado e sobrea excitabilidade cortical de 15 indivíduos saudáveis. Para isso, um estudo crossover, controlado, pseudo-randomizado e triplo cego foi realizado. Os resultados deste estudo são apresentados no artigo original intitulado “Effect of cerebellar transcranial direct current stimulation (ctDCS) on ipsilateral primary motor cortex excitability and on motor learning in the contralateral upper limb.” e sugerem que a ETCCc independente da polaridade não foi capaz de modular a excitabilidade do córtex motor primário ipsilateral à estimulação, mas atrapalhou o aprendizado motor implícito do membro superior contralateral.O segundo estudo teve como objetivo investigar os efeitos dependente da polaridade da modulação cerebelar induzida pela ETCCc sobre duas formas de aprendizado, um implícito e não específico, medido através do TRS, e um complexo, observado no teste de escrita de indivíduos saudáveis. Tratou-se de um estudo crossover, controlado, pseudo-randomizado e triplo cego, no qual 12 voluntários saudáveis foram submetidos a três sessões de ETCCc (anódica, catódica e sham) e avaliados através de parâmetros da escrita e do TRS. Os resultados deste estudo são apresentados no artigo original “Effect of cerebellar transcranial direct current stimulation (ctDCS) on procedural learning and handwriting” e apontam para uma piora no aprendizado motor medido pelo tempo de reação serial e melhora no teste de escrita após de estimulação transcraniana por corrente contínua cerebelar catódica, e uma piora no teste de escrita após estimulação anódica. Os resultados apresentados nesta dissertação confirmam a influência do cerebelo tanto no membro contralateral como no ipsilateral, sendo o último com o qual tem ligações diretas. Também foi possível confirmar que tarefas com diferentes complexidades podem apresentar desempenhos divergentes após ETCCc. Esses achados contribuem para compreensão das funções cerebelares e podem, futuramente, guiar o desenvolvimento de protocolos ideias para o uso da ETCCc como ferramenta de reabilitação de pacientes com desordens cerebelares.
Several studies have suggested that the cerebellum plays a crucial role on motor learning. Research about the effect of cerebellar stimulation on cortical excitability have been developed, however, the influence of the stimulation polarity, and the laterality of the effects are not fully understood. Another gap is the effect of stimulation on non-specific motor functions, such as the motor learning measured by serial reaction time (SRT), and complex motor tasks such as handwriting test. Those tests might have divergent results due to different mechanisms responsible for their implementation. Thus, the present thesis is composed of studies. The first one aimed to investigate the effects of transcranial stimulation current cerebellar continuous (ctDCS) on the cortical excitability of contralateral M1 and motor learning on contralateral limb in healthy subjects. For this, the effects of ctDCS on motor learning and cortical excitability were assessed in 15 health subjects in a crossover and sham controlled design. The results for this study are presented on the original research paper “Effect of cerebellar transcranial direct current stimulation (ctDCS) on ipsilateral primary motor cortex excitability and on motor learning in the contralateral upper limb“ and suggest that ctDCS, regardless polarity, was not able to modulate ipsilateral M1 cortical excitability while both anodal and cathodal ctDCS over the cerebellar cortex have disrupted motor learning with contralateral limb. The second study aimed to investigate the effects of cerebellar modulation induced by ctDCS on two forms of learning, the first implicit and nonspecific, measured by the serial reaction time task (SRTT), and the second a complex, assessed by handwriting test in healthy subjects. For this, it was adopted a crossover and sham controlled design, in which 12 healthy volunteers underwent three tDCS sessions (anodal, cathodal and sham stimulation) and assessed by SRTT and handwriting test. Results for this study are presented on the original research paper “Effect of cerebellar transcranial direct current stimulation (ctDCS) on procedural learning and handwriting” and show that both anodal and cathodal ctDCS impaired the procedural learning assessed by SRTT. For the handwrite teste, cathodal cerebellar tDCS enhanced motor learning while anodal stimulation impaired it. The results shown in this thesis confirm the cerebellar influence in both ipsi and contralateral limbs, the latter being the on it has direct connections. It was also possible to confirm that tasks with different complexities can have divergent performances after ctDCS. This findings contribute to an understanding of cerebellar functions and could, in the future, guide the development of optimal protocols for ctDCS in patients with cerebellar disorders.

This thesis deals with design of equipment for the production of PET termoplastic fibre to be used in 3D printing by means of FDM method. Concise survey of plastics processing methods is presented herein, furthermore, structural design of equipment with necessary engineering calculations is included as well. Drawing documents with the total economic evaluation is a part of this thesis too.

This thesis begins with a literature review focusing on electric vehicle (EV) applications. Systems used for steering, braking and energy storage are investigated, with specific concentration on torque control in various DC and AC motors commonly used in EVs. A final solution for a low range personal transportation EV in the form of a wheelchair is proposed. The theme for this thesis is motion control, focusing on a two axis (or two wheel drive) brushless DC hub motor (BLDCHM) EV, with torque and direction control tracking a user reference. The operation principle for a BLDCHM is documented and the dynamic and electrical equations derived. Simulation results for motor response under different load and speed conditions are compared to practical measurements. Current and torque control loops are designed, implemented and tuned on a single-axis test-bed with an induction motor (IM) load coupled via a torque transducer. A Texas Instrument DSP development kit is used for the control algorithm bench testing. The final control algorithm is then duplicated and expanded in simulation to form a dynamic two axis system for an electric wheelchair. It incorporates both motor drive and regenerative capabilities. After demonstrating two axis controls for BLDCHMs, a control algorithm is designed simulated and compared to traditional systems. The final solution focuses specifically on an intuitive response to the driver input whilst maintaining direction tracking, even when there is a difference in smoothness of the individual terrains traversed by the left and right wheels. In addition the motor drives are equipped with controllers that ensure regenerative braking in order to recover as much energy as possible when the wheelchair is commanded to decelerate.
M. Sc. Eng. University of KwaZulu-Natal, Durban 2014.

Submitted in fulfillment of the requirements for the Master of Engineering Degree, Department of Electronic Engineering, Durban University of Technology, Durban, South Africa, 2016.
The aim of this research project is to design a three phase four quadrant variable speed drive (VSD) for a permanent magnet brushless direct current motor (PMBLDC) that can be applied to an electric bicycle (e-bike). The design is confined to PMBLDC motors with a maximum power rating of 1.5kW. The speed controller operates in current mode at a maximum voltage and current rating of 50V and 30A, respectively. The VSD has the ability to smoothly control the current delivered to the DC motor and therefore controls its torque. The motor’s current is limited in all four quadrants of operation, and its speed is limited in the forward and reverse directions. The performance of the proposed DC motor VSD system is tested on an electric- bicycle. The PMBLDC motor has three hall sensors embedded into the stator to determine rotor position. A phase switcher module interprets the position signals and produces a switching pattern. This effectively transforms the BLDC motor into a direct current (DC) brushed motor. The unipolar switching scheme used ensures that current flows out of the battery only for motoring operation and into the battery during regenerative braking. The current and torque are directly proportional in a BLDC motor. Torque control is achieved in the BLDC motor using a single channel current controller. The phase switcher current is monitored and used to control the duty cycle of the synchronous converter switches. The proposed e-bike speed control system provides efficient control in all four quadrants of operation and it is a suitable alternative for a low cost transportation mode.
M

Yeung Kin.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2001.
Includes bibliographical references (leaves 86-89).
Abstracts in English and Chinese.
Abstract --- p.i
Acknowledgement --- p.iii
Tables of Contents --- p.iv
List of Figures --- p.vi
List of Tables --- p.vii
Chapter Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Distance Learning (DL) and Virtual Laboratory (VL) --- p.1
Chapter 1.2 --- Overview of related research --- p.3
Chapter 1.3 --- Web-based Control Laboratory --- p.5
Chapter 1.4 --- Contributions of the Project --- p.8
Chapter 1.5 --- Thesis Outline --- p.10
Chapter Chapter 2 --- System Architectures --- p.11
Chapter 2.1 --- Hardware Architecture --- p.11
Chapter 2.1.1 --- Internal Distributed System --- p.12
Chapter 2.1.2 --- Video Server System --- p.14
Chapter 2.1.3 --- Application Systems --- p.15
Chapter 2.2 --- Software Architecture --- p.17
Chapter 2.2.1 --- Client Side Context --- p.17
Chapter 2.2.2 --- Web Server Context --- p.19
Chapter 2.2.3 --- Software Context in Controller PC --- p.24
Chapter Chapter 3 --- System Attributes --- p.33
Chapter 3.1 --- Protocol Attribute --- p.33
Chapter 3.2 --- Client/Server Structure --- p.36
Chapter 3.3 --- Multi-layer Structure --- p.39
Chapter 3.4 --- Inter-process Flow Attribute --- p.41
Chapter Chapter 4 --- Experiment Description --- p.43
Chapter 4.1 --- Client Interface --- p.43
Chapter 4.2 --- Experiments Implementation --- p.46
Chapter 4.3 --- Controller Analysis --- p.47
Chapter 4.3.1 --- System Theory --- p.47
Chapter 4.3.2 --- PID Control --- p.49
Chapter 4.3.3 --- Set Point Control by State Space Method --- p.51
Chapter Chapter 5 --- System Characteristics --- p.54
Chapter 5.1 --- Distance Learning --- p.54
Chapter 5.2 --- Networking Issues --- p.55
Chapter 5.3 --- Design Issues --- p.56
Chapter 5.4 --- Security Issue --- p.56
Chapter 5.5 --- Interface Issues --- p.57
Chapter 5.6 --- Future Enhancement --- p.58
Chapter Chapter 6 --- Impacts and Further Work --- p.59
Chapter 6.1 --- Impacts on Web-based Laboratory --- p.59
Chapter 6.2 --- Impacts on Society --- p.60
Chapter 6.3 --- Future Work --- p.61
Chapter Chapter 7 --- Conclusion --- p.63
Appendices --- p.65
Appendix I. Selected Source Code of Server Side Programs --- p.65
Appendix II. Selected Client Experiment Interface --- p.81
Appendix III. Laboratory Experiment Manual --- p.84
Bibliography --- p.86

Dissertação de mestrado integrado em Engenharia Eletrónica Industrial e de Computadores (área de especialização em Eletrotecnia e Sistemas de Energia)
Atualmente a mobilidade rodoviária de bens e de pessoas está numa fase de mudança de paradigma para sistemas de mobilidade elétrica. Pois existe uma crescente consciencialização dos impactos negativos da utilização de veículos automóveis com motor de combustão interna, no que respeita à economia e acima de tudo às consequências ambientais. Neste sentido, os sistemas de propulsão elétrica em veículos, perfilam-se como uma necessidade para inverter a dependência energética na mobilidade rodoviária assente em combustíveis fosseis. De forma que o mercado automóvel já expõe veículos elétricos (VE), que detêm emissões de gases de efeito de estufa quase nulo, silencioso e capazes de superar a performance dinâmica dos veículos convencionais. A aposta no desenvolvimento ou conversão de um kart elétrico, segue a tendência dos desportos motorizados na eletrificação dos veículos de competição e lazer. A presente Dissertação de Mestrado tem como objetivo a implementação de um Controlador para conversão de um kart convencional em elétrico. Os elementos constituintes para este tipo de VE, são a máquina elétrica responsável pela tração, a fonte de energia elétrica e conversor bidirecional responsável pelo controlo a energia transferida entres os elementos referidos anteriormente. Numa primeira fase do presente trabalho, são descritos e estudado os elementos constituinte deste do VE, com maior enfâse no conversor CC–CC bidirecional não isolado e também no controlo deste tipo de máquina CC. Assim, de forma a demonstrar a ação deste tipo de controladores, foram também realizadas várias simulações computacionais para analisar situações aproximadas da realidade, antes das mesmas serem implementadas na prática. Numa segunda fase, foram desenvolvidos protótipos de subsistemas analisados, implementados em hardware e analisado o respetivo comportamento. Foram também retiradas conclusões e feita uma análise dos mesmos resultados.
The growing awareness of the negative impacts when using vehicles with internal combustion engines is facilitating the shifting of the transportation paradigm towards electric mobility systems. This paradigm shifting is welcome due to global economic and environmental reasons. Electric propulsion systems for vehicles is profiling itself as a necessity to invert the energy dependence on road mobility based on fossil fuels. Such that the automotive market has introduced us with electric vehicles (EV) who’s emissions of greenhouse gases are nearly null. These vehicles are quiet and also able to deliver better dynamic performance than conventional vehicles. The focus on the development or conversion of an electric kart, follows this trend of motorsports in the electrification of the competition and leisure vehicles. The purpose of this Master Thesis is to develop a Controller, for converting a conventional kart into an electrical kart. The components for this type of EV are the electric machine which is responsible for traction, the source of electrical power and the bi-directional converter, responsible for controlling the flow of energy between the elements mentioned above. Initially, the elements of such a EV are studied and described, with higher emphasis on the non-isolated bidirectional converter and energy control for this DC machine. In order to understand the action of such controllers, computer simulations were carried out to predict the system’s behavior with significant accuracy when comparing with real systems. These simulations aimed to help the decision making process before the implementation phase. In a further stage, some prototypes were developed and implemented. These prototypes were also subjected to tests and some conclusions were drawn.

Στόχος της παρούσας διπλωματικής εργασίας είναι ο σχεδιασμός και η κατασκευή του ηλεκτρικού κινητηρίου συστήματος ενός ηλεκτροκίνητου σκάφους. Πραγματοποιήθηκαν μία σειρά από τεχνικές επεμβάσεις ώστε να μετατραπεί ένα απλό σκάφος σε ηλεκτροκίνητο. Στην εποχή μας τα ηλεκτροκίνητα σκάφη και η ηλεκτρική πρόωση αποτελούν τμήμα των ηλεκτροκίνητων μέσων μεταφοράς. Τα ηλεκτροκίνητα μέσα μεταφοράς αποτελούν πιθανή λύση στην συνεχώς αυξανόμενη ζήτηση στον τομέα των μεταφορών καθώς και στα ενεργειακά και περιβαλλοντικά προβλήματα που αυτή προκαλεί. Ο υψηλός βαθμός απόδοσης των ηλεκτρικών κινητήρων και των ηλεκτρονικών μετατροπέων ισχύος, το υψηλό επίπεδο ελέγχου μέσω των ηλεκτρονικών μετατροπέων ισχύος που προσφέρει ευκινησία σε ένα σκάφος, η έλλειψη θορύβου-διαταραχών και η απουσία ρύπανσης μας οδηγούν στη χρήση των ηλεκτροκίνητων σκαφών και της ηλεκτρικής πρόωσης όλο και περισσότερο στις μέρες μας. Στη συγκεκριμένη εφαρμογή για πρακτικούς λόγους αλλά και για λόγους ασφάλειας οδηγηθήκαμε στην επιλογή κινητήρα συνεχούς ρεύματος (Σ.Ρ.) μονίμου μαγνήτη χαμηλής τάσης 24V. Αυτό έχει ως αποτέλεσμα υψηλή τιμή ρεύματος για την επίτευξη της απαιτούμενης ισχύος 1,5 kW . Για αυτό το λόγο σχεδιάστηκε και κατασκευάστηκε ο ηλεκτρονικός μετατροπέας υποβιβασμού συνεχούς τάσης σε συνεχή με διαδοχική αγωγή τεσσάρων κλάδων, ο οποίος έχει τη δυνατότητα διαχείρισης υψηλών τιμών ρεύματος και είναι ιδανικός για τέτοιου είδους εφαρμογές. Ο συγκεκριμένος μετατροπέας αποτελείται από 4 παράλληλους κλάδους, λειτουργεί στην συνεχή αγωγή και υποβιβάζει την τάση των 36V σε 0-24V για τον έλεγχο των στροφών του κινητήρα, ο οποίος έχει ονομαστικό ρεύμα 78A. Ο μετατροπέας εξετάστηκε αρχικά μέσω της εξομοίωσης χρησιμοποιώντας το λογισμικό PSpice και στη συνέχεια πειραματικά πραγματοποιώντας μία σειρά από δοκιμές και μετρήσεις. Από τις δοκιμές, παρατηρούμε ότι ο βαθμός απόδοσης του μετατροπέα διαδοχικής αγωγής που κατασκευάστηκε, κυμαίνεται γύρω στο 95%, άρα είναι μια καλή λύση στην οδήγηση κινητήρων συνεχούς ρεύματος (Σ.Ρ.) χαμηλής τάσης (υψηλού ρεύματος). Τέτοιοι κινητήρες χρησιμοποιούνται σε πληθώρα εφαρμογών ηλεκτροκίνητων μέσων μεταφοράς. Η καθέλκυση του ηλεκτροκίνητου σκάφους και οι δοκιμές που πραγματοποιήθηκαν στη θάλασσα, δίνουν σαφή εικόνα των πλεονεκτημάτων της ηλεκτρικής πρόωσης.
The object of this diploma thesis is the designing and the construction of an electric drive system for an electric boat. A number of technical interventions were made to transform a simple boat to an electrically driven boat. In our days the electric boats and the electric propulsion in general constitute a part of the electric transportation. The electric transportation may be a possible solution in the continuously increasing demand in the sector of transports as well as in energy and environmental problems that this causes. The high efficient electric machines and power electronic converters, the high control level of power electronics that offers manoeuvrability in a ship, the lack of noise - disturbance and the absence of pollution lead us to use electric boats and electric propulsion more and more in our days. In our application for practical and safety reasons we were led to the choice of a low voltage permanent magnet direct current (DC) motor. This is resulting to a high value of current to get the nominal power of 1.5 kW. For this reason an interleaved four – channel dc/dc converter was designed and constructed which has the ability to control high currents and is ideal for such type applications. The particular converter is constituted by 4 parallel channels, it is working in the continuous conduction mode (CCM) and it degrades the voltage of 36V to 0-24V for the control of the rpm of the dc propulsion motor which its full load current is 78A. Firstly a number of simulations made via PSpice program and also a number of experiments to see how the converter is working. The experiments shows that the efficiency of the interleaved converter of the application is about 95%, so it is a good solution for driving low voltage – high current dc motors. Such types of electric motors are used in many electric transportation applications. The launching of the boat and a number of sea tests shows us the advantages electric propulsion has.