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Single-phase AC circuit

AC circuits and filters · Intermediate · about 15 minutes · part of Zen’s Electronics Design Mastery

A resistor and an inductor on 220 V mains. The voltages across them do not add arithmetically because they are 90° apart. Only the resistive part consumes real power, and a capacitor can correct the power factor.

Single-phase AC circuit: the circuit on the simulator's bench

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How it works

Z = (R + rcoil) + jXL = 338 Ω + j377 Ω → |Z| = 506 Ω ∠48.1°

I = V/|Z| = 434.5 mA. P = I²R = 63.8 W, S = V·I = 95.6 VA, Q = 71.2 var

Power factor = cos φ = 0.668 lagging. VR² + VL² = Vs², not VR + VL = Vs.

Try it on the bench

  1. Note V_R + V_L is well over 220 V. The two are 90° apart, so they add as a right triangle.
  2. Close the PF switch. The capacitor supplies the reactive current, the line current falls and the power factor rises toward 1, while the real power stays the same.

Parts on the bench

In the course

Zen’s Electronics Design Mastery, module “AC & Reactance”.

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