Wind Energy Systems - Wind Energy Systems for Electric Power Generation - page 83

Fig. 5.5 Power curve of a stall turbine system

conditions, where external resistances act as load on the rotor side to increase
torque up to breakdown value during starting. Moreover slip-ring rotor machines
are suitable for cascade concepts where slip power is recovered or fed into the rotor
winding.
An equivalent circuit model of a wound-rotor induction machine is shown in
Fig. 5.8, representing a variant of the T-model in Fig. 3.3. It is called the -model

for its form of inductance parameter arrangement; another name is L-model. In the
sense of linear network theory it is equivalent to the circuit in Figs. 3.2 and 3.3 when
using a different transformer ratio:

Γ

L 1
L m k

k Γ = (5.1)

Using this definition, the leakage parameters are concentrated on the secondary
side, and equation (3.2) becomes:
U 1
U 2 / s

= ( R 1 + jX 1 ) I 1

I 2

jX 1

(5.2)

( R 2 / s + jX 2 ) jX 1

where

X 2 = ω 1 ( L 1 + L σ )= X 1 + X σ L σ = L 1 · σ R 2 = k 2

; / (1 − σ ) ;

Γ ·

R 2