Analysis of the Causes of Unstable Motor Speed in Axial-Flow Fans

Analysis of the Causes of Unstable Motor Speed in Axial-Flow Fans

Axial-flow fans are the appropriate choice for applications requiring high static pressure and are suitable for longwall mining faces. The length and extent of longwall mining faces have increased significantly. In large-scale underground mining operations, even airflow must pass through axial-flow fans. Of course, axial-flow fans have a very high friction coefficient. The primary fans used in coal mining are mainly axial-flow fans, which need to generate high static pressure to meet ventilation requirements. In some coal mines, the main fans are primarily axial-flow fans. To meet air exchange needs, very high static pressure must be generated. Some coal mines are currently testing high-speed axial-flow fans. During testing, it has been observed that these axial-flow fans produce significant noise and exhibit instability. Common issues include damage to the axial flow fan blades and bearings. Despite these problems, the methane gas emitted from the working face and the goats must be exhausted. Due to long ventilation distances and limited static pressure, this presents a significant challenge for the mine’s main fans. Axial flow fans are widely used in ventilation systems. Before longwall mining begins, ventilation shafts are excavated from the surface down to the coal seam. These are located near the rear of the mining area. As the working face retreats, the axial flow fan extracts methane from the space above it. The location and diameter of the ventilation shaft are determined based on the volume of gas to be discharged. The required capacity of the axial flow fan is determined by the amount of methane to be diluted. The depth and diameter of the axial flow fan, the required airflow, and the friction coefficient between the upper coal seam and the fan all determine the pressure within the ventilation shaft. Since the ventilation shaft requires such high static pressure, axial flow fans are the preferred choice. There are four reasons why the rotational speed of the axial flow fan motor may be unstable. 1. One of the four rectifier diodes is faulty. 2. The carbon brushes on the motor rotor and rectifier are worn unevenly. First, check the adjustable resistor of the axial flow fan. If the resistance changes when the resistor is adjusted, the potentiometer is functioning properly. The diodes carry a relatively high current; one end is secured to the circuit board with a screw, while the other end is soldered to the board with a wire and can be removed. If the connection is loose, you can check whether the diode is faulty. 3. The trigger may have various issues, such as an open circuit, poor contact, a short circuit, or failure to engage. Since the adjustment resistor is mounted on the control panel, frequent use can lead to poor contact over time.