# Transient analysis RLC in multisim-Problem?

Discussion in 'General Electronics Chat' started by electronice123, Feb 17, 2014.

1. ### electronice123 Thread Starter Active Member

Oct 10, 2008
283
0
I am conducting a transient analysis of a series RLC circuit in multisim.

Using a 10VDC power supply, a switch, a 10 Henry inductor, a 10 Ohm resistor, and a 5 nF capacitor.

My calculations show that ILmax is 223uA at 700uS.

When I perform the transient analysis I am having the following problems:

If I choose "Automatically determine input conditions" then IL peaks at 700uS, but it peaks at 35pA instead of 223uA?

If I choose "User defined" as the initial condition then IL peaks at 223uA, but it occurs at 250uS instead of 700uS?

What am I doing wrong here?

I should be getting 223uA at 700uS???

2. ### crutschow Expert

Mar 14, 2008
12,525
3,065
My simulation in LTspice gives a peak of 223.5uA @ 351μs, which seems correct and corresponds to your trace for "User Defined Input conditions".

You calculation for 700μs as the first peak point appears to be incorrect. The resonant frequency is 712Hz which has a period of 1.41ms. Thus the time to reach a peak at the first 1/4 of the wave (90° point) would be in 1.41ms/4 = 351μs, exactly as simulated.

3. ### electronice123 Thread Starter Active Member

Oct 10, 2008
283
0
Ok,

Now I understand. For some reason I was not paying attention. Ipk occurs at 1/4 the Resonant time period (90 degrees) in the circuit.

I get it now. I was just confusing myself.

Thanks!

Last edited: Feb 17, 2014