晶体管式电阻点焊电源及其复合模式控制研究

Research on transistor type resistance spot welding power supply and its compound control mode

为解决精密电阻焊过程中接触电阻变化范围大且难以预估,并由此产生焊接飞溅、虚焊等焊接质量不良的问题,设计了一种晶体管式电阻点焊电源及复合控制模式。主要介绍了晶体管式电源的主电路结构、工作原理、以dsPIC33FJ64GS610为核心的控制系统及复合控制方法。电源输出采用MOSFET开关100 kHz斩波控制,最大输出电流4000 A,能够对电压、电流反馈快速响应。复合控制模式将恒压控制与恒流控制相结合,焊接初期采用电压反馈控制适应接触电阻的变化,在短时间内降低电阻焊过程中的不确定因素,后期利用恒流模式焊接,保证焊点发热。实验结果表明,针对初期接触电阻差异大的工件结构,复合控制模式能够有效提高其焊接稳定性。

The contact resistance varies greatly during the precision resistance welding process and is difficult to predict,resulting in welding quality problems such as welding spatter and virtual welding.In order to solve the problems.a transistor type resistance spot welding power supply and a compound control mode are developed.The main circuit structure,the working principle of the transistor power supply.the control system with dsPIC33FJ64GS610 as the core and the compound control method are mainly introduced.The power output is controlled by MOSFET switch with chopping in 100 kHz,the maximum output current is 4000 A,and it can respond quickly to voltage and current feedback.The compound control mode combines constant voltage control with constant current control.In the initial stage of welding.voltage feedback control adopted to adapt to the change of contact resistance.In this way.the uncertain factors in the resistance welding process are reduced in the short time.The constant current mode is used in the later stage to ensure the welding area is fully heated.The experiment results show that the power supply and the compound control mode can effectively improve the welding stability for the workpiece structure which has large difference in initial contact resistance.