I. Selection of Variable Frequency Drive (VFD) System Choosing the right VFD for variable frequency speed control is crucial. We selected Yaskawa VFDs from Japan, a company with a dominant position in the crane industry. Since tower crane electrical controls are installed in the air, reliability is paramount when choosing a VFD. Yaskawa VFDs are among the most stable and reliable brands on the market. Cranes require high starting torque and precise brake control. Yaskawa's renowned reputation in the crane industry stems primarily from its widespread application in this sector, with each generation of products continuously improved to meet the specific needs of crane users. Yaskawa can employ either open-loop or closed-loop control in tower crane applications. We believe that open-loop control is perfectly adequate for most tower crane hoisting mechanisms. However, closed-loop control should only be considered for applications with stringent cost requirements and low VFD power. But closed-loop control requires encoders, which increase installation complexity and future product reliability in vibrating environments. Yaskawa inverters with standard software can meet the needs of tower crane hoisting, jib hoisting, trolley luffing, and slewing drives. However, Yaskawa also provides crane-specific software for customers to choose from, such as automatic upper and lower limit switches and automatic acceleration under light loads. In tower crane inverters, the speed setting method is crucial. Generally, there are multi-speed inputs, potentiometer analog inputs, and bus inputs. Multi-speed inputs can be directly set by combining the tower crane's gear position; analog inputs are provided by the PLC or resistors; bus inputs are provided by the PLC through direct communication via the bus. In practical applications, the simplest and most reliable method is to use the PLC to communicate with the inverter to transmit speed and control commands, resulting in the fewest wiring connections and the highest stability. II. Control System Selection The actual logic of a tower crane's control system is quite simple; a small PLC or relay can be used to directly drive the inverter. However, in actual projects, we have found that most maintenance personnel lack PLC knowledge. Using a PLC makes the control system a black box for them, leaving them helpless when problems arise. Relay control has a much higher failure rate than PLC, and some important protections are difficult to implement. Considering the above factors, we have introduced the American OCS integrated display and control controller, which effectively solves these problems. III. Conclusion The principle of tower crane frequency conversion control systems is simple, but the safety requirements are extremely high. A mature solution must not only meet the system's scalability and future development needs, but also consider the structural simplicity, reliability, and ease of maintenance. Chengdu Yikong Automation Engineering Co., Ltd. has many years of experience in frequency conversion drive and control for cranes. Whether you are purchasing products, system integration, or product development, choosing us will ensure you receive the most professional service. The American HORNER OCS integrated controller we use is specifically designed for mobile machinery. It uses traditional PLC control, has an operating interface, powerful network functions, a large memory for data recording, and an ultra-compact, fully integrated structure with strong vibration resistance. It is very suitable for outdoor machinery, vehicles, and other special machinery. Its panel protection level is IP65, and its maximum operating temperature is -20-70 degrees Celsius, allowing it to work excellently in various harsh environments. In all aspects, it is significantly superior to ordinary PLCs. The OCS (Optical System Control) boasts exceptional scalability, enabling direct communication with various frequency converters. It directly drives hoisting, luffing, and slewing frequency converters, and monitors their status. The OCS has two built-in analog input ports for inputting analog quantities such as trolley travel and load capacity. Optional GPS and GPRS functionality is available, requiring minimal hardware investment. It features display and operation capabilities, providing various fault indications and monitoring of various operating switches. It also allows setting parameters, such as open-loop/closed-loop control, switching directly on the screen without program modification. Key parameters can be adjusted directly based on the tower crane model, eliminating the need for program changes. The OCS also records data easily, including the frequency of faults, operator steps, and operation times. Supporting SD card storage, modifications can be easily copied and installed on-site, a convenient feature for high-altitude machinery. A larger OCS host can be added to the operator's cab for a graphical display of various operating statuses. For maintenance personnel, whether it is a frequency converter failure or an external limit switch failure, OCS will display the cause of the failure and the solution in Chinese.