Question

The voltage-arc length characteristics of a power source is V = 25+30L, where V is the operating voltage in volts and L = arc length in cm. The open circuit voltage and short circuit current for arc lengths ranging from 4 to 6 mm and for current ranging from 700 to 1000 amps during welding operation are

• A. 57 V & 1000 A
• B. 37 V & 2850 A
• C. 57 V & 2850 A
• D. 37 V & 1000 A

Answer 1

The correct option is C 57 V & 2850 A

Voltage Arc characteristics

V=25+30L

$\begin{array}{ccc}l& V& I\\ 3\text{mm}& 37& 1000A\\ 6\text{mm}& 43& 700A\end{array}$

$I-1000=\frac{1000-700}{37-43}(V-37)$

$\Rightarrow I-1000=-50(V-37)$

$\Rightarrow I+50V=2850$

$\Rightarrow \frac{I}{2850}+\frac{V}{57}=1$

$\therefore \text{OCV=57 V}$

$\text{SSC=2850~A}$