Electricity Production from Renewables Energies

3.5. Mechanical couplings between the turbine and the electric generator

3.5.1. Connection between mechanical speed, synchronous speed and electrical network frequency

In France, in private houses, the electrical energy is available in the form of a sine-wave voltage with a frequency of 50 Hz and a root mean square value of 230 V. It is thus expressed as:

[3.14]

In fact, this voltage results from a balanced three-phase system of the same frequency, identical and out of phase root mean square value of 2π /3:

[3.15]

In order to describe the elementary physical principles of electricity production, we consider three identical coils, which are supposed to be ideal (notably not saturating) and regularly spaced out in a circle of a 120° angle (Figure 3.28a). To form an electric generator, the three coils are assembled, in order to form a stator (Figure 3.28b). A magnet is placed on the rotor.

Figure 3.28. Comparison of the power characteristics according to the wind speed

When we supply the coils with these three-phase voltages, each coil creates a pulsed magnetic field. At the center of this system, the vector sum of the three magnetic fields then results in a magnetic field that turns ...