2013年7月28日星期日

Terminals in the high-voltage inverter application


With the development of market economy and automation, Nanjing three Bay Electric, said: In the improvement in the level of intelligent terminals, using high-voltage dc to ac power inverter for speed control on the pump load, not only to improve the process, improve product quality is good, but also energy efficiency and economic operation of equipment requirements of sustainable development is an inevitable trend. Speed ​​control on the pump load for the benefits of many. From the application examples, most of them have achieved good results (some saving up to 30% -40%), significantly reducing the cost of water, the water plant, increased automation, and is conducive to pumps and pipe network Buck Run, reducing leakage, burst pipes, extend equipment life.

    In the high-voltage inverter, in order to solve the multi-level unit in series voltage inverter terminals in the main control system and power unit electrical isolation between the strength and the power unit and the power unit between the electromagnetic interference problems, the paper introduces fiber connection method to achieve long-distance power transmission drives the PWM signal.

    Background

    In metallurgy, chemical, power, municipal water and mining industries widely pump load, the total energy consumption of electrical equipment 40%, electricity at the water plant and even the cost of water accounted for 50%. This is because: one, the equipment in the design, usually left a certain margin; the other hand, changes in working conditions, require different flow pump output.

    High voltage inverter system

    Figure 1 - high frequency diagram

    Unit multi-level series PWM voltage source inverter terminals, using a number of low-voltage PWM inverter power unit in series means to achieve the direct voltage output of the inverter the harmonic pollution, low input current harmonics, input power factor high, do not use the input harmonic filter and power factor compensation device. If the output voltage level to 6kV example (Figure 2), the grid voltage through the secondary side of the multiple of the step-down isolation transformer to the power supply unit, the power unit is a three-phase input and single phase output AC has a cross PWM
power inverter structure. The output of the power unit adjacent cascaded together to form a Y-linked structure, to achieve high-voltage transformer inverter output directly supply high voltage motors.

    Figure 2-6kV inverter circuit topology diagram

    Figure 3 - Schematic power unit

    Industrial fiber optic applications

    In the high frequency system, we recognize that part of the control unit cabinet is mainly weak signal, but the whole system working environment is more severe, the transmission distance uncertainty (distant), there exists a variety of high-voltage signals. If you use pure copper wire transfer, you need to face all kinds of interference, boost, buck, big loss, corrosive and other issues, leading to low reliability, practicality low resource waste results. The use of industrial fiber is a good solution to the above problems, it is bound to become part of the optical fiber communication communications major way.

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