Analysis Of Contact Closure Bounce On AC Contactor And Study Adaptive Control On Exciting Mode

AC contactor, as a low-voltage switching devices, is widely used on the field of low voltage load control and reactive power compensation. The bounce of the traditional AC contactor in the closure process could produce over-voltage, inrush current and arc phenomena. They not only bring impact and influence to load and electricity grid, but also make the contact welding which can decrease the life of AC contact. Currently, the researches of the bounce reduction almost focus on Control algorithm of the dynamic electromagnetic force. However, very few people study the substance of bounce. The paper takes the closure bounce reduction as the target and deeply study structure of AC contactor, substance of bounce and method of exciting control from three aspects:theoretical model, analysis and experiment analysis.Firstly, the paper introduced magnetic circuit method to create the static model of contactor electromagnet agency, while calculated the magnetic flux of iron core under different current and air gap. On the basic of it the paper created the dynamic model. The MATLAB is used to simulate the model and provided the theory basis to the following of analysis of bounce reduction and choice of dynamic control method.Secondly, on the base of the substance of bounce——non elastic collision, the paper found out three main reason which effect the bound of AC contactor:non elastic collision of contacts, overtravel bound and frictional vibration bound. According to reduce the quality of the AC contactor magnetic moving parts, add up the damp to the static contact and change inclination angle of static contact, the bound could be reduced from the structure. According to use the technology of synchronous phase triggered and the method of segment DC excitation voltage, the bound could be reduced the probability lastly to less than one-thousandth from the control.Lastly, the paper introduced the adaptive control technology to solve the influence of temperature change, electromagnetic interference and metal mechanical fatigue during the AC contactor working. According to sample and analyze the closure voltage, the control unit could adjust the closure process time and high exciting voltage to achieve the adaptive control of the voltage zero crossing closure and best exciting voltage method. They improved the anti-interference of AC contactor and keep the contactor’s best working performance stable..