Abstract : This paper analyzes the operating characteristics of gantry cranes, elaborates on the selection principles of motors, frequency converters, and braking methods in the speed control system when AC variable frequency speed control technology is used in gantry cranes, and describes the capacity calculation method of peripheral equipment of the frequency converter. It also summarizes several issues that should be considered in the environmental design and installation wiring of the variable frequency speed control system. Keywords : Frequency converter, gantry crane, electrical braking 1 Introduction With the continuous improvement of industrial production requirements for efficiency and product quality, the requirements for crane speed control performance are also constantly increasing. Commonly used traditional speed control methods for gantry cranes include: ① rotor series resistance speed control of wound-rotor asynchronous motors; ② thyristor stator voltage regulation speed control of wound-rotor asynchronous motors; ③ cascade speed control of wound-rotor asynchronous motors, etc. The common drawback of the above three methods of traditional AC speed control for gantry cranes is that the overall performance of the speed control system is poor, and the efficiency is low. Wound-rotor asynchronous motors have slip rings and brushes, which require regular maintenance. Faults caused by slip rings and brushes are relatively common. In addition, the use of a large number of relays and contactors results in a large amount of on-site maintenance and a high failure rate of the speed control system. The widespread application of AC variable frequency speed control technology in industry has provided a completely new solution for the wide-range and high-quality speed regulation of gantry cranes driven by AC asynchronous motors. It boasts high-performance speed regulation indicators comparable to DC speed control systems. It can utilize squirrel-cage asynchronous motors, which are simple in structure, reliable in operation, and easy to maintain. Furthermore, the efficiency of the variable frequency speed control system is higher than that of traditional AC speed control systems. Its peripheral control circuitry is simpler, maintenance workload is less, protection and monitoring functions are more comprehensive, and operational reliability is significantly improved compared to traditional AC speed control systems. Therefore, the application of AC variable frequency speed control technology to gantry cranes is the mainstream of future AC speed control technology development for gantry cranes. Compared with the widely used traditional wound-rotor asynchronous motor rotor series resistance speed control system, the application of AC variable frequency speed control technology to gantry cranes brings the following significant benefits: 1) Gantry cranes using AC variable frequency speed control technology have the advantage of precise positioning due to the rigid mechanical characteristics of the motor driven by the frequency converter. This avoids the phenomenon of motor speed changing with load variations found in traditional cranes, thus improving the productivity of loading and unloading operations. [b][align=center]For details, please click: Application of AC Variable Frequency Speed ​​Control Technology in Gantry Cranes[/align][/b]