Lincoln Electric Making Fillet Welds - Manual (Page 5)

Making Fillet Welds with Power Wave AC/DC 1000™ System
T h e f u t u r e o f w e l d i n g i s h e r e . ®
APPLICATION
5/10
Welding Guide
W A V E F O R M C O N T R O L T E C H N O L O G Y T M
Figure 8
Conventional sine waves (in red) are superimposed
schematically with Power Wave square waves to illustrate
the frequency effect. The voltage and current values are
identical for all three curves.
Square Wave Frequency
While frequency is historically accepted to be fifty
or sixty hertz, the Power Wave AC/DC 1000™ can
function at any chosen frequency between zero (DC)
and 100 hertz. Frequency can play an important role
in a specific welding procedure. Relative to a “normal”
sixty hertz, deposition rates can be slightly increased
or decreased as can penetration. Frequency alters
the total time for the arc to be at peak values. As the
frequency decreases, more time is available at peak
value and – more importantly – less time is spent in
the transition region. The converse occurs as
frequency is increased. Figure 8 (frequency effect)
illustrates this by showing what occurs during one
complete cycle.
As the frequency of the AC wave is altered, the
amount of time spent at peak current and voltage
values and the amount of time spent transitioning
from positive to negative values also changes.
In general, as the frequency is lowered, more time is
spent at peak values and less time transitioning. As
the frequency is increased, the opposite occurs.
This can be of considerable help when making fillet
welds between thick and thin members in reducing
burn-through and undercut resulting from overheating
the thinner member, as might be the case when
welding stiffeners to girder web plates. This is further
illustrated in Figure 10, (Penetration vs Frequency).