Question

In an EDM process using an RC relaxation circuit, a 12 mm diameter through hole is made in a steel plate of 50 mm thickness using a graphite tool and kerosene as dielectric. Assume discharge time to be negligible. Machining is carried out under the following conditions.
Resistance = 40 $\Omega$
Capacitance = 20 $\mu$F
Supply voltage = 220 V
Discharge voltage = 110 V
Average power input (in kW) is

• A. 0.373
• B. 0.137
• C. 0.218
• D. 0.5

Answer 1

The correct option is C 0.218

Total energy consumed
$=\frac{1}{2}C{V}^2=0.121J/cycle$

$P=\frac{1}{2t}C{V}^2=\frac{0.121}{0.55\times {10}^{-3}}J/s$

$=220W\approx 0.22kW$