Research And Realization Of Soft Starting And Energy Saving Motor Controller Based On Discrete Frequency-Control

Through regulating voltage,the traditional soft starter gives a good solution to the large starting current when motor is directly started. However, this method restrains starting torque at the same time, and the motor can’t start with heavy load. The discrete frequency-control technology without changing the main circuit of soft starter, realizes variable voltage and variable frequency through controlling the conduction of power frequency half-wave, enhances the starting torque, and starts the motor with heavy load. Besides, induction motor wastes power seriously when carries light load. In this paper, energy-saving algorithm is designed based on the regulating voltage function of soft starter, and motor’s energy-saving operation with light load is realized.Firstly, the principle of discrete frequency-control soft starting is introduced in this paper, and the most positive sequence of every generated frequency is decided according to phase sequence analysis. The specific factors which affect the starting torque of 16.7Hz are discussed. Further more, the specific problems which exist in the process of motor starting is researched, for example, the switching steps of discrete frequency-control are selected, the switching principle between steps is decided, and the speed detection without sensor is realized according to detecting the power factor angle. Secondly, in order to make the starting torque smooth, the control strategy of constant ratio between voltage and frequency is proposed. In order to reduce the voltage harmonious of generated frequency, equivalent sine control strategy is introduced. The influence on motor performance is analyzed when the load ratio changes, and energy-saving algorithm is designed and tested by simulation; Then hardware and software of the motor controller is designed and introduced based on the DSP2812.At last, the simulation model is introduced based on the MATLAB software, and the process of discrete frequency-control soft starting is simulated, the results show the advantages of discrete frequency-control starting with heavy load. At the same time, the hardware of motor controller is tested, and experiment results have verified the correctness of the controller hardware and software.