一种新型单相逆变器DQ控制策略的研究

传统的单相全桥逆变器双环控制采用电压电流的瞬时值作为反馈值,因反馈量为交流电压和交流电流,输出电压存在滞后且控制参数难以调整至最优的缺点。本文通过虚构一个与主电路参数相同、输出滞后四分之一周期的电路,做为Q轴变量,通过坐标变换,将交流信号转变为直流信号,简化了控制器的设计。     

浅谈MAG焊和埋弧焊在箱式井架的应用

从箱式井架的结构形状和焊缝接头形式出发,针对MAG焊和埋弧焊的特点进行了论述,生产结果证明,通过两种优质、高效方法的运用,使焊接质量得到了保障,生产效率得到很大提高.     

System identification of controlled pulse keyhole plasma arc welding process

The development of closed-loop control systems is one of the most effective ways to improve the stability of the keyhole status during keyhole plasma arc welding (K-PAW). Due to the disadvantages of the one-pulse-one-keyhole technology based on the conventional square current waveform, the controlled pulse welding current waveform is newly applied to control the keyhole open and close periodically. In order to realize the real-time control on the keyhole behavior with this advanced current waveform, welding experiments and system identification are conducted based on the classical control theory. One complete welding cycle can be divided into 3 periods. The keyhole establishing time is the most important time variable, which determines the keyhole behavior and welding process stability. At the same time, the averaged efflux plasma arc voltage during one pulse cycle can reflect the real keyhole dimension and status in a real-time manner. Therefore, two single-input-single-output (SISO) systems are proposed, in which keyhole establishing time and keyhole average dimension are taken as the system controlled variables respectively. Welding experiments are designed with the peak current varying randomly. Experiments show that the keyhole establishing time changes in an opposite direction to the varied peak current, and the averaged efflux plasma arc voltage varies with the same trend as the peak current. Based on the least squares technique and F test of classical system identification, second order difference equation for keyhole establishing time/peak current system and first order difference equation for keyhole average dimension/peak current system are obtained. It is proved that the calculated data by the two mathematical expressions are well matched with the measured data. The proposed research provides mathematical expressions and theoretical analysis to develop closed-loop systems for the controlled pulse K-PAW.     

基于UC3879的移相全桥式软开关弧焊逆变焊机

为将大功率软开关逆变技术应用到弧焊逆变电源中,设计了一种基于UC3879峰值电流控制模式的移相全桥软开关弧焊逆变电源,开关频率200kHz,并试制了一台5kW的弧焊逆变电源样机.实验结果显示其满足焊机工作要求,验证了设计方案的可行性,为工程应用提供了基础.