84 Practical examples
Parameter 99.05 MOTOR NOM SPEED
The value is given as generator, that is the value is greater than the synchronous speed.
Data sheet: In type testing the DFIG may be run with short-circuited rotor as motor under
nominal load. In such case there will be a speed in the data sheet that is slightly under the
synchronous speed. Calculate the difference between the synchronous speed and this
indicated speed. This difference is the ‘positive slip’.
Par. 99.05 = synchronous speed + positive slip = 1200 rpm + 5.2 rpm = 1205.2 rpm
Estimation based on equivalent circuit: The slip of induction machine is related to the
resistance of the machine.
Zpu = (Motor nominal voltage)
2
/Motor nominal power = (12000 V)
2
/2773 kW = 51.93 ohm
Rotor resistance (120 Cel) = 0.2268 ohm
R2pu= 0.2268 ohm / 51.93 ohm = 0.00436748
Synchronous speed = 1200 rpm
Positive slip = 1200 rpm × 0.00436748 = 5.24097 rpm
Par. 99.05 = 1200 rpm + 5.2409 rpm = 1205.2 rpm
99.24 XM Defines the mutual
inductance.
Mutual reactance
of equivalent circuit
DFIG characteristics value
99.25 Rr Defines the rotor
resistance, which is
reduced to the stator side.
Rotor resistance (R
r
) of
equivalent circuit
DFIG characteristics value
99.27 MAX MEAS
FLUX
Defines the maximum
measurable stator flux.
For an integrated power
cabinet with stator
switching the value is
preset at the factory.
For a medium voltage
stator switching set the
value based on voltage
transformer rating.
The ratio of the voltage
transformers.
See separate instruction
below.
99.28 MAX MEAS IS Defines the maximum
measurable stator current.
Negative value will negate
measured stator phase
currents.
For an integrated power
cabinet with stator
switching the value is
preset at the factory.
For a medium voltage
stator switching set the
value based on voltage
transformer rating.
The ratio of the current
transformers.
See separate instruction
below.
Parameter Description Source Description
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