Research Of Double-fed Motor Energy-Saving Technology Based On PLC And Inverter

In China, there is about60%of motors work in less than40%rated load. This resultin approximately30%of the energy is wasted. So the motor energy saving technology inlight load state is particularly important. Double fed motor has the characteristic ofconstant speed and adjustable power factor because of its unique rotor excitation, so it hasgreat advantages in speed control and energy saving especially for loads of pumps and fans.First, in this paper, the theory of double fed motor is studied. Double fed motor speedcontrol mathematical model is established; the basic equation of the double fed motor andits equivalent circuit is derived and then a mathematical model of the power factor controlis established. On this basis, the constant apparent power energy saving control strategy isestablished. Simulation experiments about these mathematical models and control strategyare carried out by using MATLAB software.Secondly, the PLC and general inverter control system applying research is studied.The disadvantages of traditional rotor excitation controller based on DSP and IGBT andthe advantage of new rotor excitation control system based on PLC and general inverter arecompared. The main circuit and control circuit of the energy saving control system basedon PLC and inverter is designed. At the same time, the real time parameters of double fedmotor detection circuits are also designed and the experimental system is set up.Finally, on the basis of theoretical research and simulation analysis, a large number ofexperiments are carried out. Experimental results show that the proposed energy savingcontrol theory is feasible and the expected energy saving purpose is achieved.The proposed double fed motor energy saving control technology program can saveabout half the cost than the stator side inverter and significantly improve the efficiency ofthe double fed motor. In particular, the application of constant apparent power energysaving control strategy can save a large amount of purchase and maintenance expenses ofreactive power compensation equipment.