1 Problem Statement The skirt feeder is an important piece of equipment for material conveying. Our mine has two sets of limestone skirt feeders, which feed materials to two limestone hammer crushers respectively. Each feeding system is an independent system with a maximum inlet material particle size of 800mFn. The two limestone hammer crushers crush 1.5 million tons of limestone material annually, with a crushing particle size greater than 25I lnl and a screen residue of less than 10%. The limestone skirt feeder adopts two-stage speed regulation, and the motor adopts a dual-speed squirrel-cage asynchronous motor. The motor model is: Y180L-2/4, 22kW/18.5kW. This speed regulation method is relatively backward, and the stability and economy of the equipment operation are poor. There are many problems in the operation process. (1) The particle size of the inlet material changes greatly when the crusher is running, which causes the crusher current to fluctuate up and down, and the skirt feeder speed regulation is frequent. This phenomenon causes the motor and control circuit AC contactor to burn out frequently, making the equipment operation unstable; on the other hand, it reduces the average feeding speed of the skirt feeder and the output decreases. (2) Frequent speed adjustments of the skirt feeder result in significant mechanical impact, often causing problems such as torsion cracks in the connecting large rollers and chain plate breakage. (3) Due to the relatively outdated speed adjustment method, the economic life of the crusher hammers is shortened, increasing the production cost of limestone crushing. 2. Modification Plan To address the above problems, the system must be soft-started to ensure stable operation of the skirt feeder. To increase the hourly output of the crusher, the crusher must have a suitable feed rate, requiring the skirt feeder to be adjusted at any time. Variable frequency speed control has the advantages of low-power start-up, large speed range, high precision, accurate tracking, and strong anti-interference ability. Therefore, the limestone skirt feeder feeding system should adopt variable frequency technology. The control principle of the frequency converter is shown in Figure 1, and the frequency converter setting value is shown in Table 1. [b][align=center]For details, please click: Application of ABB Frequency Converter in Limestone Skirt Feeder[/align][/b]