Active and reactive effect in AC circuit

David331 · Oct 4, 2021

Hi, I am once again asking for help regarding a AC circuit problem. This time I need to compute reactive and active effect for z=R2+C3 in the below circuit. I have already computed u(t) from before so that solves half of the problem. I am unsure if I have done the calculations correct, not much if the number-computations are correct, but if the different formulas all make sense. And if the reactive effect can be negative?

Circuit schematic with terminals A and B, a current source i0(t), R1 = 1.8k, a parallel L1 = 2.5H and C1 = 1.75u branch, C2 = 0.75u, an ideal transformer N1/N2, and a load of R2 = 4.5ohm in series with C3 = 0.25m, output voltage u(t).

Handwritten AC circuit derivation on lined paper: u(t) = 0.0946837 sin(10000t + 0.574147...) V, phasor U = 0.0946837 V, impedance Z = R2 + 1/(jωC3) = 4.5 - j0.25 kΩ, current and effective current equations, then active effect P = R Ie² ≈ 0.5565 mW and reactive effect Q = X Ie² ≈ -0.4947 mW.

magoo · Oct 4, 2021

The equations look OK to me.

If the reactive load is capacitive, then the reactive power will be negative. If you substitute an inductor for the capacitor, then the reactive load will be positive.

David331 · Oct 5, 2021

Okay now I understand. Thanks!

Active and reactive effect in AC circuit

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