Coal mine tunnel ventilation system used, plays a vital role in the production of coal mine safety in. The gas explosion in the mine is smooth with the ventilation of the roadway, and the air volume is directly related. If the ventilation is not smooth, the gas concentration will rise to a certain extent, which will cause the explosion to collapse, causing a major accident and endangering the life safety of the miners. . With the continuous extension of mining and excavation, the roadway will be extended, the required air volume will continue to increase, and the power used by the wind turbine will also increase. The alternation of the four seasons, the change of hot and cold, the required air volume also needs to be constantly adjusted, but the power of the ventilator and the dragged motor designed by the coal mine according to the anti-wind and mining operation conditions is usually much larger than the normal production of the coal mine. Required operating power.
The traditional adjustment system is realized by adjusting the damper according to the amount of air volume required. It not only wastes electric energy, but also is not convenient to adjust. Moreover, the original electric control system adopts direct or step-down starting, for high-power motors (generally in Above 55KW), the startup time is long, the starting current is large, and various protection functions for the motor are not complete. It is easy to burn the motor, causing a large impact on the power grid and even tripping the power supply system.
As a new type of power conversion device, the frequency converter has been applied to all aspects of Industrial production. It is not only easy to start, but also has significant energy-saving effects. It also has complete motor protection functions to ensure the safety of mine production and reduce production costs. To improve the degree of automation, the frequency conversion of mine ventilators has become an imperative project.
2. Types and transformation methods of mine ventilation fans
Because the mine ventilator is very important in production, it usually adopts one system, one set and two sets of systems. When one fault occurs, it can be put into another system operation safely and reliably, ensuring ventilation of the roadway. Mine ventilators are generally two types of centrifugal fans or axial fans.
We applied the frequency converter produced by our company to carry out frequency conversion transformation on four ventilators in three coal mines in Xinjiang and Shanxi. Among them, three in Xinjiang are centrifugal fans, and two in Shanxi are 660ν/500KW high-power one-to-two-axis flow fans, and the results are very satisfactory. The best power saving rate can reach more than 35%. Here we focus on the design features of the 660ν/500KW inverter produced by our company. For such a high-power inverter, if the ordinary structure is adopted, the current is relatively large, and for the 660V voltage level, the 1700V IGBT must be used. The current of such devices is currently only 200A at the maximum. Therefore, it is necessary to use 8 units in parallel operation, which is complicated in structure and bulky, which brings difficulties for installation and transportation. Because we are in the medium voltage inverter, the structure of the three-level circuit is relatively free to work, it is more reliable to work, and for high-power motors, the output waveform of the three-level circuit is also very beneficial to the motor insulation, so we The module adopting the common voltage level uses a three-level structure and adopts a unit combination method to solve the problem by using only four units, and the assembly is convenient and beautiful, the motor noise is relatively low, and the operation is relatively reliable. After being installed on site, according to the actual working conditions, the frequency can only be adjusted to 35HZ to meet the requirements, and the power saving effect is very significant.
3, the frequency conversion transformation should pay attention to the problem
Since the mine ventilator is generally a fan fan, that is, externally ventilating, a centrifugal fan is generally used, and the drag inertia is relatively large. Therefore, in the transformation, we should pay great attention when adjusting the parameters of the inverter.
Because the inertia is relatively large, in the process of stopping, the motor must enter the power generation state. If the inverter stops for a short time, the energy generated will enter the inverter to form the backflow, causing the inverter main circuit voltage to rise and damage the main device. . I have encountered a similar situation. In the first centrifugal fan inverter in Xinjiang, due to the user's unfamiliarity with the load, the adjusted parameters caused the electrolytic capacitor to burst due to the short drop time, which was caused by the overvoltage during the shutdown. The traditional treatment method is to add a braking unit, and the part of the energy is released by means of energy consumption braking. If the user has no special requirements for the downtime, the downtime of the inverter can be extended as much as possible to match the free stop time of the motor to avoid such problems.
For the acceleration time, because the load inertia is relatively large, if the motor's speed increase time can't keep up with the inverter frequency change time, the inverter will have overcurrent protection, but it can't work normally. Therefore, the speed up time should not be too short, generally it is appropriate for the inverter to work normally.
Other parameters can be set according to the parameters of the ordinary inverter.
4 Conclusion
In short, the mine ventilator adopts frequency conversion speed regulation, which not only realizes the soft start and stop, saves the electric energy, but also can conveniently adjust the speed according to the air volume requirement of the roadway, and the application effect is very ideal. There are quite a lot of coal mine enterprises in China, and the application of frequency converters in this respect should be very extensive.
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