The object of this thesis is to investigate the performance in detail and to improve the efficiency of an exterior-rotor burshless DC motor provided by a motor manufacturing company. The finite element software package FLUX3D will be adopted to conduct all the analyzing works. At first, the three-dimensional static magnetic model of the machine will be formulated by FLUX3D. After confirming the preliminary analyzing results with practical measurements, static magnetic circuit of the machine system will be established to seek the possible flux leakage paths. By adjusting the thickness of permanent magnets and the shapes of stator poles, the effectiveness of machine operational efficiency improvements as well as induced torque changes will be obtained. Finally, from these investigations, adequate suggestions for design and construct the associate machine will be provided.

Acionamentos elétricos em corrente contínua ainda são largamente empregados em plantas industriais. Os modelos usualmente adotados para os motores envolvem diversas simplificações, desprezando os efeitos da reação de armadura. Neste trabalho, foi realizada uma pesquisa bibliográfica a fim de se encontrar modelos matemáticos que contemplassem os efeitos da reação de armadura em máquinas CC. Devido à escassez de material encontrado, optou-se por desenvolver um modelo próprio com base em dados obtidos experimentalmente em ensaios de laboratório. Tal modelo, o qual foi validado através da comparação com os dados experimentais, visa a contemplação dos principais efeitos da reação de armadura tanto no circuito de campo como também no circuito de armadura. / DC motor drives are still extensively used in industrial plants. The motor models usually adopted involve several simplifications, neglecting armature reaction effects. In this work, an extensive bibliographical survey was carried on so that references of mathematical models that account for the armature reaction effects on DC machines could be found. The lack published material on the subject led us to undertake laboratory experiments on a DC machine in order to evaluate the effects of the armature current on the field circuit and on the armature circuit as well. Finally, a mathematical model was derived and validated by the comparison of simulated results with real data.

Acionamentos elétricos em corrente contínua ainda são largamente empregados em plantas industriais. Os modelos usualmente adotados para os motores envolvem diversas simplificações, desprezando os efeitos da reação de armadura. Neste trabalho, foi realizada uma pesquisa bibliográfica a fim de se encontrar modelos matemáticos que contemplassem os efeitos da reação de armadura em máquinas CC. Devido à escassez de material encontrado, optou-se por desenvolver um modelo próprio com base em dados obtidos experimentalmente em ensaios de laboratório. Tal modelo, o qual foi validado através da comparação com os dados experimentais, visa a contemplação dos principais efeitos da reação de armadura tanto no circuito de campo como também no circuito de armadura. / DC motor drives are still extensively used in industrial plants. The motor models usually adopted involve several simplifications, neglecting armature reaction effects. In this work, an extensive bibliographical survey was carried on so that references of mathematical models that account for the armature reaction effects on DC machines could be found. The lack published material on the subject led us to undertake laboratory experiments on a DC machine in order to evaluate the effects of the armature current on the field circuit and on the armature circuit as well. Finally, a mathematical model was derived and validated by the comparison of simulated results with real data.

Commutation is a fundamental feature of all DC machines. In conventional DC machines the commutation function is performed by the commutator and brushes. These act as both position sensors and switches. The mechanical commutator has obvious disadvantages. Overcoming those disadvantages has been a major reason behind the development of brushless DC (BLDC) machines. In brushless DC machines commutation is performed by power electronic devices forming part of an inverter bridge. However, switching of the power electronic devices has to be synchronised with rotor position. Position sensing is therefore an essential requirement. This can be done by using sensors such as Hall Effect devices or a sensorless approach may be adopted. Advantages of sensorless techniques include reduced cost and wiring. The most common sensorless method is based on detection of the zero crossing of back EMF signals. But this technique works only above a certain speed since back EMF is directly proportional to speed. As a result BLDC systems which rely solely on back EMF signals for commutation suffer from relatively poor starting performance characterised by back rotation of up to one hundred and eigthty electrical degrees and large fluctuations in electromagnetic torque resulting from non-ideal commutation instants. This may not be acceptable for some applications and many researchers have attempted to overcome those problems. The aim of this project has been to investigate the possibility of a sensorless technique which does not cost more than the back EMF method but with a performance at start-up comparable with that obtained when Hall sensors are used. Initial investigations led to a saliency based method. Detailed theoretical analysis is presented which shows that the method is insensitive to variations in operational parameters such as load current and circuit parameters such as power device voltage drops and winding resistances. There is a close parallel between it and the back EMF method and this makes it easy to swap to the latter method at high speed if necessary. A starting strategy, relying on saliency related measurements, is proposed which offers starting performance much better than the back EMF method and almost as good as Hall sensor based techniques. Experimental evidence is provided to confirm that commutation instants determined by the proposed method are practically coincident with those obtained when Hall sensors are used.

A drive system of the electrical lighter vehicle with the brushless DC machine is developed in the thesis. The system consists of a control unit based on a digital signal processor (DSP) and a drive module which combines a drive circuit, a brushless DC machine, and associated wheels. The motive power is delivered directly to the wheels without a power transmission system. The driving comments and the monitored signals between the modules and the control unit are communicated by the Controller Area Network (CAN) Bus. Each module can be controlled independently. By modifying the software of the system, the proposed drive system can be implemented in various electrical vehicles without changing circuit design. The developed system can be operated at forward, backward, and rotating motions. By limiting the armature current, the vehicle can be operated under the power saving mode. During the regenerative braking, the battery set is charged by the regenerative current. The experimental results show that the highest efficiency of the machine is 80 % with the motoring operation.

Tato diplomová práce pojednává o možnostech simulace a modelování elektrických pohonů na základě Bondových grafů. Je zde uvedena základní teorie k problematice. V práci jsou představeny modely stejnosměrného a synchronního stroje sestavené touto technikou. Dále je zde seznámení s Freeware knihovnou Bondových grafů BG V2.1 k programu MATLABSimulink. Za pomocí této knihovny byly sestaveny oba modely strojů. V poslední kapitole je uvedeno srovnání modelování na základě teorie Bondových grafů s modelováním v blokových diagramech.