Page 238 - Electrical Safety of Low Voltage Systems

Safety Against Static Electricity and Residual V oltages 221

FIGURE 13.5 Impulse current thresholds for ventricular fibrillation as function
of the contact duration (left-hand-to-foot path).

Solution The initial energy W C stored in the capacitor is:
1 2
W C = CV = 50 J.
0
2
The peak of the impulse current is given by:

V 0 10 4
I peak = = 3 = 10 A
R B 10
From Eq. (13.10), we calculate the root mean square value of the impulse
current circulating through the body:

10
I Brms = √ = 4000 mA
6
From Eq. (13.11), we calculate the value of the Joule integral:

3R B C
2
2
2
i (t)dt = I Brms (3R B C) = 48 × 10 −3 A s
0
The calculated value of the body current of 4000 mA, sustained for a contact
time of 3 ms, causes ventricular fibrillation with a probability greater than 50%,
as shown in the chart in Fig. 13.5.