Labo Élec

electrical lab simulator
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Exercise from the chapter "AC power"

Correction capacitor for a coil

Level 4 of 5 · Skills: Calculate

Statement

An inductive load has a resistance of 20 Ω and an inductance of 0.08 H. The supply voltage is 120 V, 50 Hz. What capacitor must be placed in parallel to raise cos φ to 0.9? (Answer in µF.)

Parametric exercise: the values change with every draw; these are one example.

2 hints from Bastaya available in the lab
Solution

Z = 32.1 Ω, I_Z = 3.74 A; P = R·I² = 279 W, Q_Z = Lω·I² = 351 var; with cos φ = 0.9: Q = P · tan φ = 135 var; Q_C = Q_Z − Q = 216 var; C = Q_C / (U² · ω) = 47.7 µF.

Course sheet of the chapter : AC power

This chapter is covered by the paths: General electricity, ISL-oriented exercises

Other exercises of the chapter

Simulated time00:00:00
Q = I·t-
W = P·t-

Workbench

Circuit diagram CEI 60617

How does it work?

The perfboard: each big hole is a circuit node. You push a single leg of a component (resistor, lamp...) into it. The 4 small holes around it are connected to it: that is where chips and leads plug in.

  1. Drag a component onto the board: it snaps onto the grid. R rotates it.
  2. To join neighbouring big holes, click Jumper chip in the palette (or C) then drag on the board: a line of chips is laid at once. Bridged holes become a single node.
  3. For long links and for the power supply (placed next to the board), drag a lead from one big hole to another (or to a terminal).
  4. As soon as a loop is closed, the circuit is solved in real time (Ohm + Kirchhoff) and the diagram follows.
  5. Zoom with the wheel (or + / −, two-finger pinch); drag the background to pan, 0 fits the board. The + buttons around the board add a row or a column.

Del delete · R rotate · C chip brush · Esc cancel · wheel zoom · drag the background to pan

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