Instruction Manual
ITEM TE700
TECNA
S.p.A.
34/128
2.5
– CONSTANT POWER OPERATING MODE (PWK)
When working in constant power mode, the inverter calculates the real effective value (RMS)
of the secondary voltage and the secondary current every mS and maintains the product
constant through a mathematical algorithm during mains voltage changes. Consequently if the
secondary resistance decreases, the welding current will increase and vice versa when the
secondary resistance increases the welding current will decrease. The adjustment in constant
power works correctly until the welding current reaches the current value set in the CURR.
MAX. parameter. On attaining said limit, the inverter automatically reduces the supplied power
in real time to limit the value of the supplied current. The supplied welding current may never
exceed the max value set for the used welding transformer. Using constant power may be
seen as a constant energy welding at a known time. In fact, when working with constant
power during the welding operation, a constant energy value is always supplied at a fixed
time.
The use of the constant power working mode may be useful to compensate the wear of the
electrodes or to weld materials that are subjected to significant resistance changes during the
welding process such as, for instance, rod welding or highly-resistive metal welding. In these
cases the current decreases during the initial welding phase in which the resistance of the
material is typically higher. As such, the squirting of molten material is avoided, phenomena
that reduce the quality of the weld.
You can see the inconstancy of the current and secondary voltage to maintain constant the
product of the two quantities and, as such, the supplied power.
