.15 Kw Intelligent Soft-start Control System Research And Design

Soft starter is widely used in the startup of asynchronous electromotor because of it' s small startup current, the economy of energy sources and reducing mechanical startup impact. With the development of machines in production area, the most excellent start performance is desired. Conventional reduced-voltage start methods start up asynchronous electromotor merely by decreasing voltage. So the startup torque is very small and can not fit the request for invariable starting torque.Basing on present status analysis of asynchronous electromotor starting technique research and development, the new method of increasing starting torque is proposed, in this paper. The new method of reducing power supply frequency in discrete steps is proposed in circuit of control system to guarantee high starting torque and small starting current at the startup time. Realization of discrete variable frequency is well researched. Considering the difference of transient voltage monotony at the zero cross of the power supply, a new method of firing angle combination of discrete frequency is found, which can produce the most positive torque. In addition, the research on how to choose the best frequencies used to discrete variable frequency control and how to change from one frequency to anther are made, which can guarantee continuity of sinusoid in discrete variable frequency starting process. The central circuit of this soft starter is made up of six thyristors in the contrary parallel connection. The central circuit is connected with AC power supply. We change burst angle to change the voltage in order to save energy.In this paper, based on theoretical analysis and simulation technique, experiment of the high torque soft starter which has Intel 16 bit single-chip computer, S87C196MH, as micro-computer is completed, the soft starter based on discrete variable frequency is also designed. The experiment approves that the soft starter can start motor smoothly with small starting current and high starting torque .The control effect are good.