Generators - Wind Energy Systems for Electric Power Generation - page 45

b)

Fig. 3.18 Operation with passive R, L load ( a ) Equivalent circuit for turbo-type machine; ( b )load
curves vs. normalized frequency

ω 1 Ψ p / √ 2 U p = j (3.21)

In the case of a coinstant load impedance the current magnitude, the torque and
the output power are functions of the frequency:

ω 1 τ
1 +(

Ψ p
√ 2 L d

L d
L tot

|

I 1 | = I B where I B =

) 2 ω 1 τ

p
L d

2 z p Ψ

2 ω 1 τ

T B = 3

L d
L tot

(3.22)

T = − T B where

ω 1 2

2

1 + τ

ω 1 2

2

p 2
L d 2

L d 2
L tot 2

τ

P B = 3

2 Ψ

P L = P B where · R L

1 + ω 1 2 τ

2

Normalized curves of current, torque and output power, with reference values
I B , T B and P B defined in (3.2) are shown in Fig. 3.18b.
For ohmic load, and assuming R 1 ≈ 0, out put power curv es vs. current with speed

as parameter are calculated by P L = 3 U p I 1 1 [ L d I 1 / U p ] 2 and shown in Fig. 3.19.

−

Fig. 3.19 Output power
characteristic for ohmic load