After a stable arc with appropriate Thermal equilibrium has been established, it is vital to keep it so that welds of consistent quality can be achieved. Normally, it is not tough to re-ignite a stable arc, even if it goes off momentarily. Whereas thousands of volts might be asked to initiate an arc at TIG welding machine, it may require only tens or in the most hundreds of volts to reignite it. Maintenance Of an arc when welding with an ac power source is quite an issue because the arc extinguishes each half cycle once the current is zero, in other words, it is going to extinguish 100 times per second using a regular 50 hertz mains supply. For re-ignition the necessary voltage has to be accessible at the time the current is zero. This is accomplished in arc welding by maintaining the voltage and current waves out of phase with a power supply with a low operating power factor of approximately 0.3.
For These circumstances, almost the complete OCV (open circuit voltage) is available to re-ignite the arc while the current is zero. The operating power factor of a power supply can be improved while maintaining the simplicity of re-ignition only by using auxiliary way of preserving or re-igniting the arc, by way of instance, a high frequency high voltage spark gap oscillator may be used to provide a high voltage pulse at the suitable instance. Such a technique is used to keep the arc, then the power factor of typically embraced for gas tungsten arc welding using an ac welding power supply. The situation could be further enhanced by employing thoriated electrode with greater electron emitting property.
In Dc welding machine that the arc maintenance is quite simple and it is just at the time of short-circuits between the electrode and the work piece that the arc is extinguished. However, this issue is solved by giving suitable dynamic volt-ampere features of the power supply. Here again electrode coatings with low ionization potential or with greater emissivity can help in simple initiation and maintenance of the welding arc.
Arc welding equipment can be carried out by ac or dc. There’s not any question of polarity because every cycle affects, if ac is employed. But if dc is used it is likely to make electrode positive or negative. More Heat is generated in most procedures using electrodes therefore in the anode. It might not be feasible to do this because, occasionally, the cleaning action of the cathode spot that is cell has to be utilized to discharge the oxide coating that is refractory in magnesium and welding aluminum, by way of instance, from the metal. In such cases it is preferable to use ac as to make compromise between cleaning actions and efficiency. Thus TIG welding equipment and carbon welding machine singapore procedures normally employ ac power sources when cleaning action on the work piece is necessarily needed.