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Has files: YesSubject: search.filters.subject.Electric locomotives

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    The study of the upgrade and improvement of power electronics protection system for locomotives
    (2023-09) Shezi, Siphesihle Brian; Ojo, Evans E.
    Power electronic processor unit used in electric locomotive for the operation of the traction AC motor has become an area of interest in South Africa. The previous locomotive uses the gate turn off (GTO) thyristors for its traction converter and this was later replaced by the insulated gate bipolar transistors (IGBTs). The replacement was due to the fact that GTO thyristor has disadvantages, as it has a complex gate drive and a moderately high power circuit was required to control the GTO thyristor. The application of the IGBT become necessary due some advantages it has over the GTO thyristor. The application of IGBT modules has the advantages in the aspect of switching, protection, power conversion and transformation. Consequently, based on the fact that GTO was replaced by the IGBT, it became necessary to carry out a study to compare both power electronics switches in order to justify this transition in the electric locomotive system. The study employed both analytical model and numerical model in the form of computer simulation to model, design, simulate and analyse the power processor unit for both switches. in this study, an extensive literature review was carried out to understand the concept of energy conversion/transformation using the power electronics switches. In comparison between the GTO thyristor and the IGBT a numerical model was developed and implemented on MATLAB/Simulink environment using the same propulsion system and the pulse pattern were used. This model was developed for the two converters topologies using the specifications for the transformer, converters and the induction motor. The computer simulation was done with the aim to justify the employment of newer types of locomotives with AC-DC-AC converter systems for the traction drive systems. Based on the analysis of the results, the power losses of an unsnubbered IGBT converter was reduced by 50% over a wide power range as compared to the GTO converter. Power losses are even reduced by up to 85% during partial load operation of the locomotive. From the simulation results, it is noted that conduction of current was fluctuating due to the switches ON or OFF states, in order to protect the locomotive propulsion and control the output voltage to the AC traction motors the variable voltage and variable frequency converter (VVVF) systems was used. Although, using the VVVF can also fluctuate the voltage, but voltage stability can be achieved by the ripple cancellation before any rectification process for the IGBT. The single control of each motor enables the use of the motors being independently controlled by each inverter at same frequency. With transistor is connected in parallel, allows the flow current in rapid way thus keeping the voltage at balance state allowing the use of components even when they are failure along the loop.
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    Autonomous switching of electric locomotives in neutral sections
    (2023-05) Mcineka, Christopher Thembinkosi; Pillay, Nelendran; Reddy, Serendra
    Abstract Electrical locomotives traversing in a neutral section must switch off as they enter a different phase voltage. The current system used to auto-switch these electric locomotives requires two pairs of induction magnets installed adjacent in-between the rails and two sensors installed underneath the locomotives. However, the return cost of investment is low, maintenance costs increase due to failures, and locomotives do not auto-switch due to the degradation of magnet strength. Additionally, damage to sensors due to animal collisions or objects also causes switching failures, and vandalism and theft are some of the challenges limiting this switching scheme. Furthermore, the latter switching method does not align with the Transnet 4.0 strategy aimed at adopting the Fourth Industrial Revolution (41R). Therefore, to align with the Fourth Industrial Revolution, this research proposed a computer vision-based approach to switch electric locomotives automatically. The requirements are a computer, a high-definition camera, and open and close markers. While the latter gives an overview of the hardware used, creating a new dataset with training and testing images allowed for developing a machine learning classification model. Firstly, image pre-processing converts the RGB images to greyscale then the noise is removed using a bilateral filter. Secondly, segmentation and marker extraction is performed by employing the Sobel operator and Circular Hough Transform. Thirdly, features are extracted using a Histogram of Oriented Gradients and employing Linear Support Vector Machine to perform classification. However, before selecting the latter classifier, the feature extractor is tested against Quadratic Support Vector Machine, K-Nearest Neighbour and Convolutional Neural Network. The model's accuracy is then measured using the training set and ground truth dataset. The test set is used to validate the model with evaluation methods such as a confusion matrix, Fl-measure and 2-fold cross­ validation.