Functional Software description
46 DCS 500 Software Description
Network reac-
tance
X
k
= 2 * π * 50 Hz * (48.85 µH + 12.5 µH)
= 0.019274 Ω
Short Circuit Cur-
rent
I
k
= √2 * U / (2 * X
k
) = 13941.33 A
Let´s calculate what will happen when DC-drive takes 400 A and β-
limit is set to 165°.
400 A load I
d
/ I
k
= 400 A / 13941.33 A = 0.0287
cos 165° = -0.966
cos (α - u) = cos α - I
d
/ I
k
= -0.9946
arc cos ( -0.9946) = 174° == > OK
600 A load Same with 600 A current:
I
d
/ I
k
= 0.043
cos 165° = -1.009
cos (α - u) = cos α - I
d
/ I
k
= -1.009
arc cos ( -1.009) = unspecified == > NOT OK, slip over
DXN The DXN is proportional network short circuit voltage and it is de-
fined by using the converter nominal current.
The purpose of DXN is to prevent the slip over of the thyristor
bridge by changing the β-limit proportionally to the converter cur-
rent, if the network is "weak". DXN is calculated:
2 * Xk * I CONV A
2 * U SUPPLY
DXN (414) =
* 1000
Parameter value for DXN (414) in this example is 43 = 4.3 %.
Scale: 1 = 0.1 %.
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