Abstract : This paper takes the renovation of a mine hoist in a mining bureau as an example to illustrate the composition and function of a variable frequency speed control system for mine hoists. A new type of mine hoist transportation system, using a PLC as the control unit and a frequency converter to regulate the speed of the motor, has broad development prospects. Keywords : Mine hoist; Frequency converter; PLC; Variable frequency speed control 0 Introduction Mine hoists are one of the key pieces of equipment in mine production. Their function is to hoist coal and ore, transport personnel and equipment, etc., occupying a very important position in the entire mine production process. Currently, in mine hoists, the AC drive speed control method, which can be applied in situations requiring high power, torque-type loads, and a large speed range, mainly uses rotor resistance (metal or liquid resistance) speed control of wound-rotor asynchronous motors. This series resistance speed control method uses a controller or magnetic station to combine resistors of different resistance values ​​connected in series with the rotor to achieve speed regulation. However, it has obvious drawbacks, mainly reflecting very low efficiency, as it increases slip power consumption to reduce speed. The slower the rotational speed, the lower the efficiency, with most of the power being converted into heat and wasted. Using inexpensive AC induction motors and a variable frequency drive (VFD) solution can effectively solve this problem. VFD achieves motor speed regulation by changing the stator power supply frequency. Regardless of the speed, its mechanical characteristics are essentially parallel to natural mechanical characteristics, and the slip power consumed remains basically constant, resulting in high efficiency, significant energy savings, and greatly improved speed regulation smoothness. It has achieved significant economic benefits in energy saving, reduced maintenance, and increased product output and quality. It represents the future direction of motor speed regulation. This article takes the renovation of a mine hoist in a mining bureau as an example. The original mine hoist used a YRKK-355 wound-rotor motor with series resistance speed regulation, which consumed a lot of energy. Therefore, it was replaced with VFD. The motor was replaced with a 2200W, YB80-355L three-phase asynchronous motor. The frequency converter used was an LG SV220iH-4, and the PLC was a SIMATIC S7 series S7-300, equipped with digital and analog input/output interfaces and corresponding monitoring and communication plugins. It boasts a large signal processing capacity and fast processing speed. The existing old electrical control equipment was also upgraded. The entire control device is connected to the control room via shielded cables, and the control room includes motor start/stop buttons. The frequency converter cabinet also has manual/automatic switching buttons for convenient operation. [b][align=center]For more details, please click: Application of Variable Frequency Speed ​​Control in Mine Hoists[/align][/b]