#VFD history.
At the end of the 19th century, three-phase ac and three-phase asynchronous motors were invented. 60-70% of the electric energy is used by various motors, 80% of which is used by AC motors and 20% of which is used by DC motors. Dc motor is mainly used in high performance variable speed transmission. Three-phase asynchronous motor has simple structure and reliable operation. Dc motor structure is complex, with brush conduction, but the speed performance is good, in nearly a century dc motor in the field of speed control. It has long been known that ac motors can adjust their speed by changing their frequency, but it is difficult to achieve this because of technical problems.
In the 1970s, power electronics and microelectronics technology developed by leaps and bounds, which laid a foundation for the birth of #frequencyconverters. Just then, an oil crisis swept the world and energy conservation became a top priority.
People first found that fans and pumps are driven by asynchronous motors at constant speed, and control flow with valves and baffles, which is extremely wasteful. If speed control is adopted, electric energy can be greatly saved. After the first generation of frequency converters appear, speed control can be carried out, energy saving 20%-30%.
In the 1980s, with the development of semiconductor technology, especially microprocessors and thyristors, it was possible to control the conduction state of thyristors. In this way, the drop closing of the upper and lower bridge switching elements is controlled by the microprocessor, and the DC electrical changes can be converted into AC current, which is what we often call frequency conversion technology; at the same time, we can adjust the power components . , the opening and closing action cycle can be adjusted to the output frequency of the inverter.
Finally, combined with rectification technology, we can change the standard frequency of the grid and the frequency of the power supply required to change the motor frequency and achieve the speed of the motor speed. Tuning controls; through long tech development and scientists, frequency converters are upgraded and evolved in secondary applications, slowly moving to the way we see them today.
Zhejiang SHUYI Electric Co., LTD,
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