What kind of fluctuations are present at the line voltages (3p 4wire) when the load is welding machine... What kind of fluctauations/disturbances in input voltages can be present at the worst case when the load is welding machine (I donot know about the power rating/specs about welding machines)........lets say if harmonics are present what kind of harmonics/if the input voltage wave gets disturbed?....what is the worst possible care should be taken when neutral is connected in these kind of loads?....