Hi all, my question is regarding the constant voltage charactersticks in GMAW. Also called as flat charactersticks, for a small change in voltage there is a large change in current and this is designed to maintain a same arc length. I am reading a book which says that when CTWD increases then arc length (arc voltage increases) so an arc current(melting rate) is decreased for a fixed wire feed speed to maintain a same arc length.By doing so, electrode extension increases so deposition rate will increase but penetration will decrease with increase in electrode extension. Conversely, if CTWD decreases then reverse happens and penetration increases.
My question is that is this variable penetration/deposition  is acceptable? What is the purpose of maintaining same arc length?

I know its a very basic question but i am having hard time in understanding it. Any response will be highly appreciated.
Thank you all in advance.