Elec Class

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Solved exercise · level 5 of 5

Workshop: tubes, motors and heaters

Skills: Calculate

Statement

A workshop supplied at 220 V, 50 Hz is lit by non-compensated fluorescent tubes drawing 5 A with cos φ₁ = 0.8, and equipped with 3 motors of 2200 W useful power, efficiency 0.7 and cos φ₂ = 0.75 each. What active, reactive and apparent powers does the workshop need when everything runs? What does the overall cos φ become if two 2000 W heaters are added?

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 = P₁ + P₂ = 880 + 9429 = 10310 W; Q = Q₁ + Q₂ = 660 + 8315 = 8975 var; S = 13670 VA; cos φ = 0.754. With 2 × 2000 W more active power, cos φ = 0.847.

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
delete
R
rotate
C
chip brush
Esc
cancel
wheel
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fit the board
drag background
pan

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