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Comments on Peak current in series LC resonance circuit

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Peak current in series LC resonance circuit

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In the following series LC circuit , maximum input current (IL1) reaches to 321mA in the simulation which is decided by V1/2 x π x f x L1 (f being resonant frequency).

why total impedance seen by V1 is not addition of inductor and capacitor impedances but only inductor impedance?

In series LC resonance both impedances (XL=XC) cancel each other then how come current does not reach infinity ?

Ltspice simulationseries LC step response

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maximum input current (IL1) reaches to 321mA in the simulation which is decided by V1/2 x π x f x L1 (f being resonant frequency).

Given that both capacitor and inductor have equal magnitude impedance at resonance, you can also see that the same formula applies for the capacitive reactance. So, what is your point exactly? You found a formula that worked and stopped right there without delving more deeply? Maximum current also occurs when the capacitor voltage also equals the input step voltage (and inductor voltage is zero). All these things are related and a little bit more complicated than just simple observations.

why total impedance seen by V1 is not addition of inductor and capacitor impedances but only inductor impedance?

Impedance is a steady state AC parameter and it's much more mathematically complicated when circuits are driven with a transient voltage step change. You need to use Laplace transforms for example.

In series LC resonance both impedances (XL=XC) cancel each other then how come current does not reach infinity ?

Because your input voltage is a transient step change and not a continuous sinewave at the resonant frequency.

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You found a formula that worked and stopped right there without delving more deeply? (2 comments)
You found a formula that worked and stopped right there without delving more deeply?
kadamrohan16‭ wrote about 1 year ago

Andy aka‭ It was an observation from simulation which i wanted to clarify as i am not able to grasp what are the factors which limit peak current . laplace transform is the tool to understand more about the peak current ? please suggest.

Andy aka‭ wrote about 1 year ago

Studying LC resonant circuits can be a whole book worth of learning. It begins with differential equation solutions then leads onto understanding Laplace transforms and then understanding pole-zero diagrams (plus a lot of stuff in between).