Research On The Control Technology Of Soft Start And Step-down Energy Saving Of Asynchronous Motor

Three phases asynchronous motors,which are widely used in various industries as power load.So it’s starting control and saving-energy operation have always been the focus of attention.For directly starting of large and medium-capacity asynchronous motors,it is easy to cause instantaneous current overload and starting torque oscillation,which bring impacts to motor and even affect motor’s life.Moreover,most of the motors are belong to light-load or even no-load conditions for a long period of time,resulting in low energy conversion efficiency and serious waste of electrical energy.In order to limit the motor starting current and improve the operating efficiency under light load conditions,the soft start and energy saving operation can be realized by controlling the thyristor ac regulator.This thesis focuses on the research of soft start and step-down energy saving control technology of motor,the main contents are as follows:(1)Deeply researching the loss and power transfer relationship of motor,the basic principles of soft start and step-down energy saving are studied,and the voltage regulation characteristics of AC voltage regulator with different types of loads are analyzed,an accurate motor model of considering the iron loss is set up.The simulation results show that the equivalent resistance of iron loss is essential in the study of dynamic process and loss calculation.(2)Aiming at the defects of current-limiting soft start control,a current-limiting soft start control strategy based on linear active disturbance rejection control is proposed for better motor starting current and starting torque,and the stability of controller is analyzed.By comparing the control effect of LADRC control strategy and traditional PID control strategy,it verified the control effect and anti-disturbance characteristics of LADRC,which helps to achieve the smooth start of the motor.(3)In order to achieve the optimal energy conversion efficiency in the light load operation of motor,the input voltage control strategy based on the optimal voltage method is proposed,and the LADRC is applied to the design of the step-down energy-saving controller of motor,which can achieve the quickly tracking the optimal input voltage of the motor,so that the power factor and energy conversion efficiency of the motor can be improved with the load changing.Finally,the validity of controller is verified by comparing of the simulation.(4)In order to verify the correctness of theoretical researching,the motor experiment platform is designed and built.The platform is used to test the effect of soft starting and step-down energy saving of the motor,and comparison of the test effect of energy saving under different load rates.The test results show that the desired design effect can be better achieved by the designed energy saving controller.