Production Welding Concepts

What is Arc Recovery Time and Arc Characteristics in Electric Arc Welding Process?

The time taken for establishing the arc between electrode and work piece is called as Arc Recovery Time.This article focus about Arc Recovery Time and Arc Characteristics  in Electric Arc Welding Process in a detailed way which is mentioned below.

What is Arc Recovery Time and Arc Characteristics in Electric Arc Welding Process
What is Arc Recovery Time and Arc Characteristics in Electric Arc Welding Process

Explanation of Arc Recovery Time

  • Establishing the arc means establishing the flow of electrons and ions in their respective directions.
  • In DC Arc welding,because the terminals are fixed,whatever may be the arc recovery time ,it doesnot have any influence on the welding operation.
  • Whereas in AC Arc welding,because the terminals are continuously changing,the arc recovery time should be less than the cycle time(C.T).

But,for effective Arc Welding operation,the Arc Recovery Time (ART) must be less than half of cycle time i.e. ART < (C.T/2)

  • The Arc Recovery Time can be reduced by increasing the voltage of power supply i.e. by increasing the voltage of power supply,the reaction time for producing electrons and ions will be reduces.

            If V ≅ 30V      Then,

                      ART ≅ (C.T/2)

                      It means that as Voltage(V) increases,it reduces the ART.

  Max. Voltage ≤70V    i.e. Voltage is {30V,70V}

  • The range of Voltage used in the AC Arc welding is (30V-70V)

Stable Equilibrium Conditions of Electric Arc Welding Process

  • To ensure the stable Equilibrium conditions of Arc welding process and Arc welding Equipment,whatever the energy supplied by using power supply unit is only has to be utilized at the Arc point.
  • To ensure the above conditions,the energy supplied by using power supply unit is controlled by using the voltage and current settings of power source whereas energy utilization at the Arc point is controlled by using ARC LENGTH.
  • Therefore,for stable Equilibrium conditions,it is required to determine the optimum arc length and optimum settings of a power source

Vo -Open Circuit Voltage (or) Actual EMF generated in 2°windings of a transformer(or)Max Voltage in 2°

Is-Short Circuited Current (or) Max. current which is possible to pass through the 2° windings.

Rs-Resistance of 2° windings

The Resistance of 2° windings = Vo/Is

where

                           V = Vo-Vdrop

                              =Vo-(Rs*I)     

            V  =Vo-({Vo/Is}*I)

Arc Characteristics in Electric Arc Welding Process

As mentioned above that,

L – Arc Length

I – Current

Is- Short Circuited Current.

                                       If       L =0,I=Is,Rair =0

                                                L=large,I=0,Rair=∞

then

                  Vair = I*Rair

i.e.             Va   =a+bL                                    where a,b are constants.

At stable Equilibrium condition,the voltage in power source = Voltage in Arc point

    i.e.                     Vp =Va

                                                                                                  ⇒Va = Vp

                                                                                               a+bL =Vo-[{Vo/Is}*I]

                                                                                            [{Vo/Is}*I] =Vo-a-bL

 

                                      I = {Is/Vo}*(Vo-a-bL)

Since Power P = V*I

                           =(a+bL)*{Is/Vo}*(Vo-a-bL)     

For minimum power supply,Derivate the above equation w.r.t Length(L) and equate to zero.Then you can get an equation in terms of ARC LENGTH(L)

This is the complete explanation of Arc Characteristics in electric arc welding in a detailed way.

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