| Steel has always been an irreplaceable material during the development process of human society.In the past three decades,the iron and steel industry and its continuous casting technology have grown rapidly in china,furthermore,great accomplishment and success has been achieved.Continuous casting is the process that the molten steel is continuously casted into billet.In general,during the solidification process of molten steel,phenomenas such as Central segregation,Central porosity and shrinkage would happen frequently.In order to improve the quality of continuous casting steel,electromagnetic stirring(EMS)technology for continuous casting emerged as times required.EMS technique for continuous casting plays an important role in both surface and internal quality improvement of billet.Low-voltage variable-frequency conversion power supply is an important part of EMS control systems,so precise variable-voltage and variable-frequency control is the guarantee of high-quality continuous casting electromagnetic stirring process.Firstly in this paper,the development history and trends of continuous casting electromagnetic stirring technology are introduced,and then the development directions of EMS technology in the future are summarized;In the next section,The structure and working principle of the electromagnetic stirrer system are explained with the billet electromagnetic stirrer system as an example,including electromagnetic stirrer unit,frequency conversion power supply,water cooling system as well as remote monitoring unit;Frequency conversion power supply is the focus of this study,this paper analyzes the working principle and control technology of the variable-frequency power supply in detail,expatiates the topology structure and principle of the main circuit,and gives the current and frequency closed-loop control strategy based on SPWM.Then the hardware and software design of the variable frequency power supply system are introduced,then the main circuits of the hardware are introduced and the program flow chart of each functional software is given.Finally,in Hunan Zhong Ke Electric Co.,Ltd billet electromagnetic stirring system experimental platform was built,applying the control method that introduced above.Then the experiment and analysis were carried out on the experimental platform to verify the feasibility of the control strategies and obtain the corresponding experimental waveforms and experimental results.Through the comparison between the product with electromagnetic stirring technology and that without electromagnetic stirring technology,we can found that electromagnetic stirring technology can significantly improve the quality of billet. |
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