Complex sentence: The arc length is kept constant by using the principle of a self-adjusting arc i.e., if due to certain reasons arc length decreases, arc voltage will increase, arc current and therefore burn-off rate will increase thereby causing the arc to lengthen.
Split into simpler sentences: The arc length is kept constant by using the principle of a self-adjusting arc. If the arc length decreases, arc voltage will increase, arc current and therefore burn-off rate will increase thereby causing the arc to lengthen.