Counter-Rotating Type Power Technologies to Exploit Offshore Energies

Double Rotational Armature Type Generator

The author has prepared the peculiar generator composed of the inner and the outer rotational armatures, without the traditional stator. Figure 1 shows the performances of the model synchronous generator (3-phase, 4-pole, permanent magnet, AC generator with double rotational armatures), where the rated output P = 1kW at the induced frequency f = 50Hz and the induced voltage E = 100V while the relative rotational speed N_T = 1500min^-1. Figure 1a shows the relation between the outer armature rotational torque T_F* and the inner armature rotational torque T_R*, in keeping the rotational speed of the outer armature constant at N_F = 750 min^-1, while changing the rotational speed of the inner armature N_R at the various external loads. These rotational torques do not include the mechanical torques such as the bearings in the generator, and T_R* is given by the absolute value though the direction of T_R* is against T_F*. It is obvious that T_R* coincides with T_F* irrespective of the relative rotational speed (N_T = N_F – N_R) and the output/load, because the rotational torque should be always dynamically counter-balanced between both the armatures. That is, the rotational torque counter-balances dynamically between the inner and the outer armatures. The relative rotational speed affects the output P and the induced voltage E against I_G, as shown in Figure 1b. The output increases with the increase of the induced voltage E at the same I_G, while E is in proportion to the relative rotational speed N_T.

Figure 1.

Performances of the model double rotational armature type generator: (a) rotational torque, (b) output, induced voltage, and electric current