A1 and A2

[niga]

Hello there.

Can someone give some good website which explains abt damping in RLC series and parallel circuits?I am trying to understand the equations in RLC,how to get the A1 and A2 in the various damping conditions.

Looking forward to hearing from u guys.

With Thanx always for the help exended so far and all ur time

niga

 

[Russlk]

From my handbook, when 4*L/(R^2*C)=1, the circuit is critically damped (fastest response). When 4*L/(R^2*C)<1 the circuit is over damped (non-oscillating). When 4*L/(R^2*C)>1, the circuit is oscillating.

 

[niga]

hey russ thanx for ur quick response.
the equation is

Ld^2i/dt^2 +Rdi/dt+i/C=dV/dt

for overdamped case the solution is Aexp s1t+B exp s2t.

my problem is with finding the values of these A and B

 

[ljcox]

Ld^2i/dt^2 +Rdi/dt+i/C=dV/dt

for overdamped case the solution is Aexp s1t+B exp s2t.

my problem is with finding the values of these A and B

You find A & B by considering the initial conditions, ie. where t = 0.

If you need more help, I suggest you post the circuit.

Len

 

[niga]

Thankyou Len,

 

[niga]

attachment

 

[mstechca]

What is A1 and A2?

 

[niga]

Ld^2i/dt^2 +Rdi/dt+i/C=dV/dt ...........(1)

for overdamped case the solution is
i=A1exp s1t+A2 exp s2t.

my problem is with finding the values of these A and A1
find i' and i" substitute into the eqn 1.
if its dc dV/dt=0

am i right?

 

[ljcox]

Ld^2i/dt^2 +Rdi/dt+i/C=dV/dt ...........(1)

for overdamped case the solution is
i=A1exp s1t+A2 exp s2t.

my problem is with finding the values of these A and A1
find i' and i" substitute into the eqn 1. No just use i and i'
if its dc dV/dt=0 Yes

am i right?

Here is a start for you. Let me know if you need more help.

I suggest you check my algebra, I may have made errors.

Len

 

[niga]

Thankyou for ur most helpful and descriptive answer.But if i may pls ask of u to chk this attachment.

 

[niga]

1. in order to find K,i' and i'' are found, put into the eqn 2(ur attachment) and equated to dV/dt.As its an ac supply we have an RHS but had it been DC it wud have been dV/dt=0

so Ld^2i/dt^2 +Rdi/dt+i/C=0
in which case we get k=0
does this mean there is no particular solution?
duh. :shock: ..i am sorry if i am asking really dum qs but i don get it

2. in case of a parallel circuit
the difference wud only be in the equation?
Icoswt=V/R+1/L integral V dt+C dV/dt

-wIsinwt=dV/R +V/L +v(0) +C d^2V/dt^2

the following procedures are the same as in series.

 

[ljcox]

1. To find K you only need i and i' you don't need i". You obtain i' from my eq 1. ie the one with the integral since Int i dt = 0 if i = 0.

If DC then there is no ip.

2. Yes

I'll look at your attachment next.

Len

 

[ljcox]

Thankyou for ur most helpful and descriptive answer.But if i may pls ask of u to chk this attachment.

See the attachment.

Len

 

[niga]

Okay Len,I get it.(finally!)
so that clears my head with r l and c's.
phew!hey,but, its always Thanx to u!!!

 

[niga]

oh,oh but len i just came across some notes which say prticular solution is assumed
Acoswt+Bsinwt.....that is kcos(wt+phi)....sheesh...i am ?or it doesn matter?u can take both ways?kcos(wt+phi) and kcos(wt+phi+theta)?

 

[ljcox]

Acoswt+Bsinwt = kcos(wt+phi) if the applied voltage is V cos wt or V sin wt, ie. the phase angle is zero.

Len

 

[niga]

Yup,thanx len.