RL with Circular Wave Source

A "circular wave" voltage source V S ( t ) V_S(t) excites an R L RL circuit as shown. The source voltage is zero at time t = 0 t = 0 . It consists of semicircles of radius π / 2 \pi/2 , with alternating polarity. The period of the signal is 2 π 2 \pi seconds. See the attached image.

At time t = 0 t = 0 , there is no current in the circuit. In steady state, after initial transients have died out, what is the peak instantaneous value of the current?

Details and Assumptions:
1) R = 0.1 R = 0.1
2) L = 1 L = 1
3) All quantities are in standard S I SI units


The answer is 1.921.

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1 solution

Karan Chatrath
Jan 1, 2021

Great start to the year!

First, the triangular wave signal's equation is computed, which is:

V S ( t ) = { π 2 4 ( t ( 2 π n + π 2 ) ) 2 2 π n t < ( 2 π n + π ) π 2 4 ( t ( 2 π n + 3 π 2 ) ) 2 ( 2 π n + π ) t < ( 2 π n + 2 π ) V_S(t)= \begin{cases} \sqrt{\frac{\pi^2}{4} - \left(t - \left(2 \pi n + \frac{\pi}{2}\right)\right)^2} & 2\pi n \leq t < (2\pi n +\pi)\\ -\sqrt{\frac{\pi^2}{4} - \left(t - \left(2 \pi n + \frac{3\pi}{2}\right)\right)^2} & (2\pi n + \pi ) \leq t < (2\pi n +2\pi)\\ \end{cases}

n = t 2 π n =\biggr \lfloor \frac{t}{2 \pi}\biggr \rfloor

Having obtained V S ( t ) V_S(t) the circuit equation is:

L I ˙ + I R = V S ( t ) L\dot{I} + IR = V_S(t) I ( 0 ) = 0 I(0) = 0

I have avoided doing this analytically. So numerical integration takes care of the rest. The following plot is hopefully illustrative:

Here, I have compared the current response due to the circular wave source with that of the triangular and sinusoidal sources. This plot strengthens my assertion about the fact that the magnitude of the current response is higher as the source supplies a higher magnitude of energy per unit current.

@Karan Chatrath Happy new year

Talulah Riley - 5 months, 1 week ago

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Same to you

Karan Chatrath - 5 months, 1 week ago

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@Karan Chatrath So ,what are your planning in this new year ,?

Talulah Riley - 5 months, 1 week ago

Thanks for the solution. I am also becoming more convinced that the current magnitude is proportional to something like the area under the curve for a half period of the source.

Steven Chase - 5 months, 1 week ago

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