Optimum Design Of Dry-type Transformers

Dry-type transformers have advantages over oil-immersed transformers, so they have been widely used in recent years. Currently, the design level of most transformer manufacturers still remains low but the production ability keeps increasing. Because optimum design is important to improve efficiency, save production costs and enhance market competing capability, this dissertation makes a systematic study on dry-type transformers'optimum design.An optimum design model is established after the hand design method and dry-type transformers'structure are studied. The cycling-method is applied to accomplish the optimum model, and how to reducing huge-searching area and decreasing lengthy-calculating time are studied. Principles to choose cycling variables are introduced, and methods of determining cycling variables'boundary statically and dynamically are provided by utilizing the reactance restriction condition. Then the optimum design process is created based on the above.The steady-state temperature rising of the dry-type transformer is studied. Using traditional methods, calculating results of high voltage and low voltage windings'temperature rising are always greater than experimental data. Based on analyzing characters of cooling surfaces, and considering the high work temperature, modified formulas are given to enhance the accuracy. In order to balance part temperature rising of the low voltage winding, the surface average temperature rising and the hottest point in each part of the low voltage winding are discussed and calculated.The object-orient method is taken to model the dry-type transformer and UML is employed to describe the optimum design software. Entity-classes and interface-classes are defined after requirement analysis, and sequential diagrams are built after use-cases of the software are analyzed, thus the structural model and active model are settled. Based on these models, C++ programming language is selected to develop the software.During the optimization there're lots of self-defined objects. To manage these objects, traditional methods are complex or inefficient. By using Standard Template Library a new method is presented to solve the dynamic memory allocation and release problems.The software can not only optimize dry-type transformer design but also check results of hand design and manage the data it stored. Design instances generated by the software are compared with previous designs, and optimization ways of these instances are presented, which shows that the software has attained the original goal. A large number of calculations indicate that the software can be used practically.