研究与设计一种新颖的电容放电焊机——双电容佯谬电焊机

A new type of condensor discharge welding machine——The welding machine with a"Two capacitor paradox circuit"

为了解决当前电焊机存在功率因数不高和高次谐波的问题,并且试图使当前的电容放电焊机体积缩小,质量减轻,采用两项措施:(1)将双电容佯谬电路引入到目前的电容放电焊机的放电回环,即将当前电容放电焊机中的储能电容器C一分为二。其中一组C1留在放电开关(如SCR)的左端,另一组C2接在开关(SCR)的另一端,使之形成"C1-SCR-C2"形结构。(2)在焊机进线端安装新型静止无功补偿器。改进后的焊机其出现在焊接工件上的电压和电流始终都具有同样的波形,同一的相位。因此,焊接时电路中只有有功功率的流通,不出现无功损耗和畸变损耗,电容器所储电能全部成为焊接所需的有功功率;本焊机的放电开关(SCR)中仅流过焊件中工作电流的一部分,从而减小了SCR的电流定额和散热器的体积;焊接电流和电压均为负指数衰减函数,其波前十分陡峭(垂直时间轴90°),容易引弧和维持电弧稳定;焊接功率也是负指数衰减函数,控制规律简便,有利于实现波控法和熔滴控制等。该焊机减少了该焊接设备的无功功率和高次谐波等,并缩小了焊机体积,减轻了质量。

In order to avoid electric pollutions by the condenser discharge welder,let us introduce a new circuit topology of such welder.First,let the＂two capacitor paradox circuit＂ be introduced in the discharge loop of the condenser discharge welder.Namely, there are two discharge capacitors （C1 and C2） in the discharge loop.C1 is connected to the point in front of SCR,C2 is connected to the point after SCR.They are formed a＂C1-SCR- C2＂structure.The second step is connecting a new static VAR compensator using a selfhealing AC capacitor to a joint between electric source and welder.The voltage and current in welding workpiece are always with same waveform and exactly in phase anywhere,so that there is no reactive power,no high harmonics,only active power flowing in circuit. The current passing through SCR is only a part of that in welded workpiece.Therefore,the current rating of SCR may be decreased, and its radiater may be smaller too.With a negative decreasing exponential curve,the wave front of current and voltage are very steep （almost 90 degree with time axis）.It is easy to produce a stable electric arc.The bonding power of this welder also has a negative decreasing exponential curve.This control rule is easy and helps to realize waveform control method and droplet control.This welder becomes,not only,no reactive power,no harmonics in its circuit,but also,it will be light in weight and contraction in volume.