The Research Of Energy-saving Controller For Asychronous Motor Under Periodic Loads Condition

The AC asynchronous motor because of its simple structure and inexpensive cost, widely used in industry and agriculture fields. but when it works, the motor has the load often to be at the varying duty, if in the under-loading or the idling working conditions, appears the asynchronous machine power factor to become lower, the efficiency reduced, the electrical energy wasted and so on. therefore under almost constant speed and periodic loads conditions in the asynchronous motor, energy-saving is extremely essential.Firstly, the thesis detailed has carried on the power loss analysis of the asynchronous motor based on T -type equivalent circuit andГ-type equivalent circuit, has indicated it not accurate for the traditional division of the loss, has divided and calculated the total loss again under periodic loads condition. Then the energy-saving principle of voltage-regulation under periodic loads condition is derived analytically and the voltage-regulation curves of asynchronous motor are given. Based on that, the control range and energy-saving effects of several control algorithms are compared and validated by simulation. The thesis has proposed the control strategy for power factor angle to the energy-saving system by fuzzy query table finally. Take freewheeling angle deviation and the change rate of freewheeling angle deviation as input and take the increment of shutdown angle as output, the thesis has established D-fuzzy controller and obtained the query table of fuzzy control. Through reducing the asynchronous motor terminal voltage real-time following loads diversification by shutdown angle to enhance the power factor, the purpose of energy-saving has been achieved.Sencondly, based on Matlab/Simulink, the thesis has established the simulation model of soft-starting and energy-saving controller for asynchronous motor, focused on the work principle of modules for shutdown angle control and energy-saving control. The simulation results can have seen that starting current decreased in the soft-starting process of asynchronous motor and the terminal voltage of the asynchronous motor reduced following loads diversification by shutdown angle to enhance the power factor to expected value whether under periodic loads condition or under sudden loads condition, then verified feasibility of the energy-saving strategy based on fuzzy control in Chapter 2.Finally, based on theoretical analysis, the hardware circuit of soft-starting and energy-saving controller has been designed to seeking simple, economic and reliable. The hardware part consist of many circuits, like the main control chip selection(dsPIC30F2011), the voltage synchronous signals circuit, the drop signals detection circuit, the SCR triggering circuit, the DC power supply circuit,the keyboard and the display circuit. The voltage synchronous signals circuit and the drop signals detection circuit both constitute the power factor detection circuit. In addition, the software design main include soft-starting part and energy-saving part. the software flow chart has been drafted and then focused on the programming of the energy-saving part.