Question

Linked Date Question (Q.9.62 - Q.9.63):
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

The time for one cycle, in milliseconds, is

• A. 0.55
• B. 0.32
• C. 0.89
• D. 0.24

Answer 1

The correct option is A 0.55

Cycle time:
$T_c=R.C.ln\left(\frac{V_s}{V_s-V_d}\right)$

$=40\times 20\times {10}^{-6}\times ln\left(\frac{220}{220-110}\right)$

$=0.55\text{milli seconds}.$