Cable sizing calculation sheet with formulaFull description
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Descrição: Choppers Conversores CC-CC
Reference : Unistar High Voltage XLPE Cables - Catalogue Formula Used : KVA Full load current = KV x
3
Short circuit current A = Ish x
t k
Where t = short circuit time in sec k = constant
Voltage Drop VDROP =
3 * IFL * (R COS f + X SIN f) * L KV * 1000 * N.R
%
Where IFL = Full load current of the Load connected in Amps KVA = Rating of the Load connected KV = System Voltage R = Resistance of the cable in Ohm/Ph/KM X = Reactance of the cable in Ohm/Ph/KM L = Length of the cable in meters N.R = No of Runs of the cable cosf = Power factor of the system Voltage Dip VDIP =
3 * IST * (R COS f + X SIN f) * L KV * 1000 * N.R
%
Where IST = Starting current of the Motor in Amps KVA = Rating of the Load connected KV = System Voltage R = Resistance of the cable in Ohm/Ph/KM X = Reactance of the cable in Ohm/Ph/KM L = Length of the cable in meters N.R = No of Runs of the cable cosf = Starting Power factor of the system Derating Factor o Ambient temperatu temperature re correction correction factor for 50 C = Group derating factor Multi Core cables For 3 circuits, derating factor run in air= 0.92 Therefore the Total derating factor = 0.83x 0.92= 0.7636
0.83
1.1Primary Air (PA) fans Load = KV =
2700 kW 11 2700
Full load current =
=
165.75
=
165.75 0.76
=
217.1
A
3 x 11 x 0.9 x 0.95 Total derating Factor
=
0.76
Current to be carried by the cable
Short circuit current = A =
40
40 x
0.16 94
A
kA x
1000
= 170.21
331
A
2
mm
Considering 3C x185 cable 3C x 185 XLPE cable can carry Voltage drop 3 x
165.75
=
x(
11000 0.121
0.211 x
x
0.9 + 0.0968 x 0.435 ) x 0.2 x 100
1
Voltage dip Starting Current = = = 3 x
745.86
=
4.5 x Full load Current 4.5 x 165.75 746 A
x(
11000 0.545
0.211 x
x
0.9 + 0.0968 x 0.436 ) x 0.2 x 100
1
Conclusion 1 x 3C x 185 XLPE, AL conductor, armoured cable
