In the high-voltage frequency conversion system, we realize that the signal in the control unit cabinet part is mainly weak, but the working environment of the whole system is relatively bad, the transmission distance is uncertain (long distance), and various high-voltage electric signals exist. If pure copper wire is used for transmission, it will face various problems such as interference, boost, depressurization, large loss, and easy corrosion, resulting in low reliability, low practicability, and waste of resources. The use of industrial fiber is a good solution to the above problems, so fiber-optic communication will inevitably become the main way of communication in the future.
     In the improvement of the intelligent degree of the terminal block, the high-speed inverter is used to control the speed of the pump load, which not only improves the process and improves the product quality, but also meets the requirements of energy saving and economic operation of the equipment, and is an inevitable trend of sustainable development. There are many benefits to speed control of pump loads. From the application examples, most of them have achieved good results (some energy savings of up to 30%-40%), greatly reducing the water production cost of the water plant, increasing the degree of automation, and is conducive to the pump and pipe network. Step-down operation reduces leakage and tube explosion and extends equipment life.
    In the high-voltage frequency converter, in order to solve the strong and weak electrical isolation between the main control system and the power unit in the terminal of the multi-level high-voltage inverter of the unit series, and the electromagnetic interference between the power unit and the power unit, the adoption is proposed. The fiber connection method enables long-distance transmission of power-driven PWM signals.
    The pump load widely used in the metallurgical, chemical, electric power, municipal water supply and mining industries accounts for about 40% of the energy consumption of the entire electrical equipment, and the electricity cost even accounts for 50% of the water production cost in the waterworks. This is because, on the one hand, the equipment usually has a certain margin when it is designed; on the other hand, the pump needs to output different flow rates due to changes in working conditions.
    The unit series multi-level PWM voltage source type inverter terminal block adopts several low-voltage PWM frequency conversion power units in series to realize direct high-voltage output. The frequency converter has small harmonic pollution to the power grid, low harmonic input current, and input power factor. High, no input harmonic filter and power factor compensation device are required. For example, taking the output voltage level of 6kV as an example, the grid voltage is stepped down by the isolation transformer of the secondary side and then supplied to the power unit. The power unit is a three-phase input, single-phase output, and the AC power supply type inverter. structure. The output ends of the adjacent power units are connected in series to form a Y-connected structure, and the high-voltage direct output of the variable voltage frequency conversion is realized, and is supplied to the high-voltage motor.