Intelligent wind power unit with tandem wind rotors - Wind Power Generation and Wind Turbine Design - page 352

the rear wind rotor N R in the lower wind velocity than 12 m/s, but scarcely affects the
speed of the front wind rotor N F regardless of the wind velocity V . Besides, the rear
wind rotor starts to counter-rotate at the slower wind velocity with the decrease of
the bulb load. The relative rotational speed N T = N F N R contributes proportionally

to the induced voltage E , the induced electric current I G depends on the load, and the
output P is obtained electrically from

−

√ 3 EI , while given mechanically by Tw T ( T =

T F = T R , w T : the relative angular speed). Within the measured data, the operating

condition with the bulb load 1023 W gives the higher output P .

−

5.4 Trial of the reasonable operation

As recognized in the above discussions, the performances are affected not only by
the wind velocity V but also by the blade setting angles b F , b R and the bulb load.
Then, this wind power unit was operated impractically but reasonably, in trail, by
changing the rear blade setting angle b R and the bulb load, while keeping the front
blade setting angle b F = 20°. The output was kept constant at P = 430 W in the
wind velocity higher than V = 12.6 m/s, and the unit was operated at the optimum
rotational speed giving the maximum output in the slower wind velocity. Figure 30
shows the reasonable operation, where the adjusted rear blade setting angle and
bulb load are denoted with ( b R (°), P bulb (W)), and the experimental data are plot-
ted and represented by the curve. The bulb load P bulb is not related directly to the
output P because the bulb resistances are affected by the fi lament temperature

600

( b R deg., P bulb W)

(30,600)

(30,723)

450

(20,900)

(20,1023)

300

P =430 W

(20,725)

b F =20deg.

150

(30,1023)

(30,900)

V =12.6 m/s

0

800

400

N F

0

N R

-400

-800

0 4 8 12 16 20

V m/s

Figure 30 : Trial of the reasonable operations.