Design Of Power And Control System And Research On Melting Control Method For Large Electroslag Furnace

Large electroslag furnace refers to a kind of electroslag furnace which can melt the ingot over30t. Due to the increase of melting tonnage, the size of crystal mould has increased and at the same time, melting power supply, melting process, and control strategy are also changing. It is not just simple scaling of small electroslag furnace.Based on the project of80t electroslag furnace, this thesis analyses the process requirements and equipments requirements systematically, and completes the design of control system and power system. According to the characteristics of large electroslag furnace load, we select a kind of transformer named T-transformer which can change the three-phase power into double single-phase power. The unbalanced degree of three-phase power can be alleviated by using T-transformer as the power supply of electroslag furnace. Based on the principle of T-transfomer and the actual characteristics of electroslag furnace load, the thesis analyses the influence of three-phase balance on the primary side when using different wiring modes in the process of melting. According to the test data, the thesis also analyses the existing mode on the power supply of T-transformer and proposes an improved power supply mode. How to ensure the balance of three-phase power in the melting process is also been researched and discussed.The control system consists of PLC and superior computer. Using the PLC which is produced by GE company to configure the hardware design. Meanwhile, a redundant network is configured which can ensure the continuous operation of the melting process. It controls the entire smelting process. The program of superior computer is written by IFIX software, which can collect, display and processing all the melting data.Due to the nonlinear and time-varying characteristics of electrode lifting system of large electroslag furnace, based on the traditional PID control and actual production situation, the thesis designs the controller by using fuzzy PID algorithm and carries out the computer simulation which provides the theoretical basis for the application of actual project in the next stage.