And with the constant development of control technique and control avenue, frequency variation speed controlled has developed the vector controlled frequency variation velocity modulation, by controlling the AC motor inside act for shunt DC motor field coper’s flux, to enhance the permanent torque output scope and static and dynamic character, make the AC motor frequency variation speed controlled system superior to DC motor voltage variation speed controlled system. For simplifying the control system, reducing the fault rate, there has developed a vector controlled frequency variation speed control without speed sensor which based on the vector controlled frequency variation speed control. In some application which have low require , vector controlled frequency variation speed control without speed sensor could completely compare with the vector controlled frequency variation speed control that have speed sensor. The vector control has the epoch-making significance to the AC current motor velocity modulation.
Frequency variation speed control is the best way in the motor speed modulation, it is the perfect gear in the company’s technical reform and product renewal, it is the essential composition in the industrial automatic system, it is the assumption of realizing the automatic of product proceed and management, it is also the precondition in the development of informationization. In our country’s traditional estate, using the DC motor speed control actuation account about 85%~90% in the speed controlled system, but the AC speed controlled system account about 10%~15%. Low efficiency, bad quality, large cost, high fault rate have already been the bottleneck that restrain the development of the company. So, we must promote the advanced AC frequency variation speed control technique positively, arms the traditional industry with the advanced equipment, promote a further development in the automation, the industrialization and the informationization.
1.2 Our Country’s Development Condition in Speed Controlled Technique
Our country is a developing country, so many product’s research ability has behind the developed countries. From now on, the product of frequency variation speed controlled that ourselves made only act for last century 90s in the international. With the reform and opening, rapid development of economic, forms a large market, it opens to the country companies, also the foreign companies. Many products are exported from the developed countries, and runs well in our country, satisfied our need in fabrication and living. Many co-partership companies in our country make the international advanced products. The domestic complete department independently is designing the manufacture in the complete set installment to use the foreign import company and the joint venture supposes advanced each, own develop the application software, can provide the first-class electrical transmission control system for the domestic and foreign important engineering project. Although obtains very many result, but should see because domestic develops, the production product ability voluntarily is weak, is serious to the overseas company's dependence.
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