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Solved exercise · level 4 of 5

Lamps, heater and motor

Skills: Calculate

Statement

An installation at 230 V, 50 Hz has 10 lamps of 40 W, a 1500 W heater and a motor of total power 1800 W with cos φ = 0.8. What active, reactive and apparent powers do all these loads absorb together? What is the overall cos φ and the current drawn from the mains?

Total active power.

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

1 hint from Bastaya available in the lab
Solution

P = 10 × 40 + 1500 + 1800 = 3700 W; Q = P_motor · tan φ = 1350 var; S = √(P² + Q²) = 3939 VA; cos φ = P / S = 0.939; I = S / U = 17.1 A.

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-

Circuit diagram CEI 60617

How does it work?

Each big hole is a circuit node: you push one leg of a component into it. The 4 small holes around it are connected to it: chips and leads plug in there.

  1. Place a component Drag it from the palette: it snaps onto the grid. R rotates it.
  2. Bridge neighbouring holes Pick the jumper chip (or C) and drag on the board: bridged holes become a single node.
  3. Draw a lead For long links and the power supply: from one big hole to another, or to a terminal.
  4. Close the loop The circuit is solved live (Ohm, Kirchhoff) and the diagram follows.

Shortcuts

Del
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R
rotate
C
chip brush
Esc
cancel
wheel
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drag background
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