DESIGNER IM649 User guide

Appendix B B-3
STT WAVE SHAPING PRINCIPLES
WAVE DESIGNER
27850060
BACKGROUND AMPS
PINCH AMPS
PEAK
AMPS
TA ILOUT
T
1
T
2
T
3
T
5
T
6
T
7
T
0
FIGURE B-2. WELD DROPLET TRANSFER.
• From time T
0
to T
1
: Background current is a steady-state current level, between 50 and
(Background Current) 100 Amps that maintains an arc to form a weld bead.
• From time T
1
to T
2
: An arc voltage detector indicates that the arc is shorted; background
(Ball Time) current is reduced for approximately 0.75 milliseconds.
• From time T
2
to T
3
: High current is applied to speed the transfer of molten metal to the
(Pinch) weld puddle. A dV/dt calculation indicates when fuse separation is
about to occur; current is reduced to 50 Amps.
• Time T
4
: Fuse separation occurs at low current. Time T
4
is a function of
(Fuse Separation) voltage, and not indicated on the amperage waveform.
• From time T
5
to T
6
: A period of high arc current that melts the electrode back.
(Plasma Boost)
• From time T
6
to T
7
: Arc current is reduced from Peak Amps to the Background current
(Plasma) level.