Inverter Welder

AC electrodes are frequently operated with the simple, single phase transformer with current adjusted by means of tappings or sliding core control. DC rectifiers and ACDC transformer-rectifiers are controlled electronically, for example by thyristors. A new generation of power sources called inverters is available. These use transistors to convert mains AC (50Hz) to a high frequency AC (over 500 Hz) before transforming down to a voltage suitable for welding and then rectifying to DC. Because high frequency transformers can be relatively small, principal advantages of inverter power sources are undoubtedly their size and weight when the source must be portable. Electrode holder and cables The electrode holder clamps the end of the electrode with copper contact shoes built into its head. The shoes are actuated by either a twist grip or spring-loaded mechanism. The clamping mechanism allows for quick release of the stub end. For efficiency the electrode has to be firmly clamped into the holder, otherwise poor electrical contact may cause arc instability through voltage fluctuations. Welding cable connecting the holder to the power source is mechanically crimped or solderedIt is essential that good electrical connections are maintained between electrode, holder and cable. With poor connections, resistance heating and, in severe cases, minor arcing with the torch body will cause the holder to overheat. Two cables are connected to the output of the power source, the welding lead goes to the electrode holder and the current return lead is clamped to the workpiece. The latter is often wrongly referred to as the earthlead. A separate earth lead is normally required to provide protection from faults in the power source. The earth cable should therefore be capable of carrying the maximum output current of the power source.