Electricity Production from Renewables Energies

3.6. Generalities on induction and mechanical electric conversion

The synchronous machine is an electric machine technology that is used to convert the mechanical power into electric power. To illustrate the physical principle of synchronous machines, we consider the experiment which consists of making a magnet turn in front of a fixed coil, whose terminals are connected to an oscilloscope (Figure 3.29).

Figure 3.29. The motion of a magnet in front of a coil

If the angular speed of the magnet has a constant value Ω, on the screen we observe a sine-wave periodic curve. By definition, the magnetic flux characterizes the intensity and the spatial distribution of the magnetic field through a surface. Figure 3.30 shows that in one complete revolution of the magnet, with a duration the total magnetic flux φ through all the coil spires successively takes:

– at the instant t = 0, the maximum value φ_m;

– at the instan t , a null value;

– at the instan t , the value −φ_m ;

– at the instan t , a ...