Finding wavefront and wavetail times

1. STUDY MATERIAL FOR AMIE & RECRUITMENT EXAMS
HIGH VOLTAGE ENGINEERING
AMIE(I) STUDY CIRCLE(REGD.)
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Example (AMIE S14, 14 marks)
A ten-stage impulse generator has 0.25 F
capacitance. The wavefront and wavetail resistances
are 75 ohm and 2600 ohm, respectively. If the load
capacitance is 2.5 nF, determine the wavefront and
wavetail times accurately of the impulse wave.

2. STUDY MATERIAL FOR AMIE & RECRUITMENT EXAMS
HIGH VOLTAGE ENGINEERING
AMIE(I) STUDY CIRCLE(REGD.)
AMIESTUDYCIRCLE.com
Solution
See following figure for analysis.
Here R2 is neglected and the time taken for charging
to peak value is approximately three times the time
constant of the circuit. During charging C1 and C2 are
in series.

3. STUDY MATERIAL FOR AMIE & RECRUITMENT EXAMS
HIGH VOLTAGE ENGINEERING
AMIE(I) STUDY CIRCLE(REGD.)
AMIESTUDYCIRCLE.com
Therefore,
1 2
1 1
1 2
3C C
t R
C C



4. STUDY MATERIAL FOR AMIE & RECRUITMENT EXAMS
HIGH VOLTAGE ENGINEERING
AMIE(I) STUDY CIRCLE(REGD.)
AMIESTUDYCIRCLE.com
During discharge C1 and C2 are in parallel and R1 and
R2 in series. Hence the time for 50% discharge is
approximately given as
t2 = 0.7 (R1 + R2) (C1 + C2)
Using these formulae, we have
18
1 9
3(25)(2.5 10 )
(75)
27.5 10
x
t
x


 =
9
511 10 sec 0.511 secx 

and
9
2 0.7(2675)(27.5) 10t x 
 = 51.5  sec