Arc welding power sources-arc characteristics, Mechanical Engineering

Assignment Help:

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


Related Discussions:- Arc welding power sources-arc characteristics

What are the forces acting on foundations, What are the Forces Acting on Fo...

What are the Forces Acting on Foundations Foundations are normally subjected to vertical loads which are resisted by compressive stress generated in the soil. However, the acti

About Transfer Function block, How can i change the normal function block p...

How can i change the normal function block parameter[1 1]=>(s+1) to (s-1)?

Development of coated electrodes, DEVELOPMENT OF COATED ELECTRODES C...

DEVELOPMENT OF COATED ELECTRODES Can welding be done by bare wire? Why do we require coating at all? What are the different types of coating? What are the stages in

Rapid prototyping, Give justification toward the development of rapid proto...

Give justification toward the development of rapid prototyping?

Explain caustic stress corrosion cracking, Q. Explain caustic Stress Corros...

Q. Explain caustic Stress Corrosion Cracking? Dilution of the caustic prior to injection into a relatively hot stream will minimize the potential of caustic Stress Corrosion Cr

Sialons, Sialons Mixture of silicon nitride, aluminium nitride and alu...

Sialons Mixture of silicon nitride, aluminium nitride and alumina is hot pressed to acquire a product largely called as sialon. In the resulting product the structure has part

Discover the maximum torque, Discover the maximum torque: Discover the...

Discover the maximum torque: Discover the maximum torque that may be transmitted by the shaft of 400 mm diameter, if the shear stress is not to exceed 50 N/mm 2 . Solution

Steam , how to calculate the volume of HFO burn to produice steam?

how to calculate the volume of HFO burn to produice steam?

Calculate the unit step time response for a system, (a) Calculate the unit ...

(a) Calculate the unit step time response for a system with pulse transfer function (b) Calculate the pulse transfer function of a unity feedback discrete time system with

Explain cutting speed - cutting parameters, Explain Cutting Speed - Cutting...

Explain Cutting Speed - Cutting Parameters It is relative speed (V 1 ) between wheel and the Work piece. It is expressed in m/sec.   V=Cutting speed=V 1   =

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd