Abstract : This paper analyzes and describes the application of the ControlLogix PLC system and 1336 Force AC frequency converter in the tilting system of the Jiuquan Iron & Steel (JISCO) 2 million kW converter, considering the mechanical characteristics and process requirements of the motors. Keywords : PLC, Frequency converter, Tilting, Automatic Control JISCO's 2 million kW steelmaking plant has three 120t top-and-bottom blown converters. Converter #1 was put into operation in April 2005, and converters #2 and #3 were put into operation in early 2006. The tilting and oxygen lance systems of all three converters utilize Rockwell Automation's Allen-Bradley Logix platform control system (ControlLogix), NetLinx network architecture (ControlNet), and 1336 Force AC frequency converters based on field-oriented vector control technology. This enables automatic control of the converter tilting and oxygen lance systems. The self-diagnostic and protection functions are reliable, reducing equipment downtime and significantly improving production efficiency. 1. Analysis of Converter Tilting Load Characteristics In the converter system, the tilting mechanism uses four tilting motors, rigidly connected by reducers, and employs a fully suspended fixing method and a torsion bar torque absorption method, as shown in Figure 1. [align=center][b]For details, please click: Application of Rockwell PLC and Frequency Converter in Automatic Control of Jiuquan Iron & Steel Converter Tilting[/b][/align]