Arc welding power sources-arc characteristics, Mechanical Engineering

ARC CHARACTERISTICS


In order to understand the different output characteristics that are required by the welding power source it is necessary to understand the load which is fed by the welding power source. In arc welding processes the load is nothing but the arc itself. In order to select the right source, it is essential to know the load characteristic, namely arc characteristics.A general arc characteristic is shown in Fig.(a) Since the negative slope region (dotted line) of the arc occurs at very low arc currents, it is usually neglected and a simplified arc characteristic is assumed as shown in Fig.(b).

2223_art characterstics 1.jpg

 

It is also known that as the arc length changes the characteristic (arc voltage for a given current) changes. Longer arcs require higher arc voltages Fig.(a) For the same arc length if we increase the arc current then the arc voltage increases (as though the arc is a pure resistive load obeying ohm's law) Fig.(b).Therefore the arc voltage is function of two variables namely arc current and length for  given gas.

 

666_arc characterstics 2.jpg

Fig.  shown how the operating pointis achieved by the intersection of the source and arc characteristics. In Fig.(a) the source has high open circuit voltage (OCV). The characteristic is drooping. Hence, there is a lot of difference between OCV and actual arc voltage. Where as the drooping curve meets the X-axis at a point called short circuit current (lSC). In Fig .(b), the power source has low open circuit voltage (OCV) and the source characteristic is such that the output voltage changes slightly with load current. Therefore, the arc voltage is almost equal to the source OCV. We can fix arc voltage with flat characteristic power source by controlling the OCV.

1290_arc characterstics 3.jpg

 

For changes in arc length the arc characteristic will change. But, this will have different effects with flat
and drooping characteristic power sources. As shown in Fig. (a) with a drooping characteristic power source and changing arc lengths we can see that the change in arc voltage is considerable. Where as with a flat characteristic power source, the change in current is considerable, but the change in voltage is less, as shown in Fig .(b). With the above things considered, let us see now what type of output characteristics are required for each of the arc welding processes.

 

 

 

 

 

1967_arc characterstics 4.jpg

Posted Date: 9/14/2012 2:53:32 AM | Location : United States







Related Discussions:- Arc welding power sources-arc characteristics, Assignment Help, Ask Question on Arc welding power sources-arc characteristics, Get Answer, Expert's Help, Arc welding power sources-arc characteristics Discussions

Write discussion on Arc welding power sources-arc characteristics
Your posts are moderated
Related Questions
I have an assignment and i want you to do it for me

a misile is fired at speed v and an angle m that is inclide at an angle r to the horizontal.calculate the range

what do you mean by compounding of turbine?explain pressure-velocity compounding with neat sketch.

Q. Define pattern colour code? The patterns are normally painted with contrasting colours such that the mould maker would be able to understand the functions clearly. The colou

Graphical simulation animation of a CAD system can be used to inspect the tolerance and interference of matching components of a product. It will be possible to precisely define

applications of dynamically induced emf

Use of Labour-based and Appropriate Technology: The construction and maintenance of rural roads can generate a good level of employment. Hence, the technology used should be

Illustrate with required expression for dynamically equivalent system. Illustrate in detail about the Balancing of Radial Engines.

Time and Cost Analysis This discusses about certain basic activities that must be carried out in a factory to convert raw materials into finished products. These activities br

I am attending Thermodynamics class at the university. The professor asked me to write a research on Renewable Energy: Solar Power. The report should be of 10 pages and at least 10