Abstract : This paper analyzes the feasibility of using an AB PowerFfex70co medium-voltage frequency converter to modify the control of the blower, introduces the principle and characteristics of variable frequency speed regulation, and the expected operating effect in blower control. Analysis shows that this medium-voltage frequency converter can achieve stable adjustment for a 6000V, 3150KW high-voltage high-power motor, with reliable operation and significant energy-saving effect. Keywords : Medium-voltage frequency converter, variable frequency speed regulation, control 1. Problem Statement The original converter secondary dust removal system had insufficient suction capacity and could not effectively seal the upper part of the furnace mouth. Therefore, during molten iron charging, blowing, and semi-steel tapping, a large amount of flue gas was emitted to various operating platforms and released into the atmosphere through the plant's skylights. Therefore, to completely solve the converter dust removal problem, the secondary dust removal system must also be modified accordingly. Based on these changes and the "15th Five-Year Plan" for molten iron desulfurization technology modification, during operation, a large amount of high-temperature flue gas permeates the plant, and the existing exhaust hoods are not ideal in their collection effect. Therefore, to effectively address the workshop's dust pollution problem, the renovation of the dust removal system is imperative. To this end, it was decided to comprehensively renovate the dust collector fan control system, utilizing AC variable frequency speed control to achieve airflow control, energy saving, and adjustable speed control, thereby ensuring that dust emissions meet standards. 2. Selection of Variable Frequency Speed ​​Control Scheme The dust collector fan's motor is a high-voltage, high-power motor with rated parameters: UO=6000V, P=3150 KW, necessitating the use of high-voltage variable frequency technology. Currently, there are three internationally adopted high-voltage variable frequency schemes: Y-Δ conversion, high-low-high variable frequency speed control system, and direct high-voltage variable frequency speed control system. The first two schemes both use transformers for voltage reduction. The Y-Δ conversion system, as shown in Figure 1, requires the AC asynchronous motor to be connected in a delta configuration. While this scheme meets the voltage and current requirements, it has poor tolerance to dU/dt and common-mode voltage. The high-low-high frequency conversion speed control system, as shown in Figure 2, allows for the use of inexpensive low-voltage frequency converters, but requires two transformers (step-down and step-up), reducing energy efficiency. Furthermore, the transformers require corresponding start-stop and protection devices, increasing costs and the equipment footprint. The direct high-voltage frequency conversion speed control system, without any intermediate steps, is the most direct and convenient solution and is currently the best option for high-voltage, high-power motor frequency conversion speed control. Its simple principle is shown in Figure 3. [align=center][b]For more details, please click: Application of PowerFIex700O Medium-Voltage Frequency Converter in Dust Removal System Control of Steel Plant[/b][/align]