Mine inverter using considerations
Due to the special environment and safety requirements of coal mine production, the application of frequency converter in coal mine started relatively late. At present, there are few flameproof inverter products that meet the requirements of coal mine safety. With the further development of the market economy in our country, the production increase, consumption reduction and efficiency improvement of coal mines have been put on an important position. Energy-saving equipment reform is also imperative. Mine frequency converter in the coal mine fixed machinery and shearer has also been a certain application and achieved good results. So, mine inverter should pay attention to what in the course of what?
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First of all, it is a leakage protection problem. Since the inverter output voltage is PWM wave, the output current is close to the sine wave, but the input current wave is not a standard sine wave, and contains the harmonic wave of the equivalent composition, thus causing malfunction of the earth leakage protection system or interfering with the detection signal Routine leakage detection can not be used in the inverter power supply circuit, you should use a dedicated leakage protector. But now the mining feed switch is the use of conventional leakage detection principle, after using the inverter, most of the leakage caused by power.
Current treatment methods are mostly in the leakage protection test circuit parallel high-voltage capacitors, eliminating the detection of high harmonics signal "glitch"; followed by the use of optimized leakage protection parameters, according to 30mAS (milliampere seconds) principle, to reduce leakage current , Enlarge the leakage protection time, make its product remain the same. In addition, the frequency hopper leaking electricity leakage protection, although with the frequency changer power source characteristic, but also has the relations with the feed switch, the different manufacturer feed switch protection 整 定 different, must conscientiously study the instruction book. Sometimes, the feed switch protection plug-in problems, will cause the feed trip, this time often users will get our inverter to say, so we must carefully check and analyze the reasons for the correct treatment.
In the use of the inverter, pay attention to the importance of a good grounding, grounding wire cross-section to meet the requirements, while grounded very good grounding, grounding resistance is less than 3 ohms, these will eliminate interference and so will have a certain effect.
Second, the fan pump load, according to the motor rated voltage / rated current / rated power, select the appropriate inverter. For constant power loads such as belt conveyors, select the inverter that adapts to the operating characteristics according to the load conditions, such as transporting the belt conveyor or lifting the transport winch, and selecting the inverter with four quadrant characteristics. The power of the inverter should refer to the rated motor The current is selected and is greater than the motor rating to meet the requirements of heavy load start.
For the deep well pump (submersible pump) load, different from the general pump load, due to the distance between the inverter and the motor, you need to increase the output sine wave filter to improve the output voltage and current waveforms to increase drive performance; inverter drive pump load , The drainage pump is a cubic characteristic load, that is, the higher the speed is, the more the resistance is. Therefore, the starting time of the inverter should not be too long, otherwise the pump will not be able to form a vacuum and not be put on the water. Effect ", or damage to the pipeline, causing serious accidents. For fan load, debugging, pay attention to the free rotation of the fan blades cause the inverter to start overcurrent, so in the commissioning to increase the DC braking before the start of the link, the first leaves the fan stationary, and then start the motor running.
Third, the inverter heat dissipation: For non-explosion-proof Guiji on the ground, pay attention to the matching position between the reactor and other heating devices and inverter, try to avoid "circulating wind", that is, the reactor hot air into the inverter, thus affecting the cooling effect. For mining explosion-proof inverter, most of the current use of heat pipe cooling technology, but also the use of water cooling technology, cooling system design, mainly according to different power levels to design, and reference inverter module power dissipation parameters (including the pass loss and Switching loss) calculation, and leaving a margin, the cooling effect for the stable operation of inverter and life have a significant impact. When using the heat pipe cooling cooling mode, in the field use, should also pay attention to the installation and use of the environment, the inverter should be placed horizontally, non-"backwards", otherwise it will affect the heat dissipation. Also need to regularly clean the surface of the radiator dust, or else it will affect the cooling effect.