Functional Software description
46
DCS 500 Software Description
Network reac-
tance
Xk = 2 *
π
* 50 Hz * (48.85
µ
H + 12.5
µ
H)
= 0.019274
Ω
Short Circuit Cur-
rent
Ik =
√
2 * U / (2 * Xk) = 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
Id / Ik = 400 A / 13941.33 A = 0.0287
cos 165
°
= -0.966
cos (
α
- u) = cos
α
- Id / Ik = -0.9946
arc cos ( -0.9946) = 174
°
== > OK
600 A load
Same with 600 A current:
Id / Ik = 0.043
cos 165
°
= -1.009
cos (
α
- u) = cos
α
- Id / Ik = -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 %.
Содержание DCS 500B
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