Question 1: (50 marks)
It is required to supply a 3-phase, 400 volts, 300 kW motor for a distance of 100 m. The motor load is known to have a power factor of 0.9376 lagging.
a) Calculate the size of a suitable PVC insulated copper cable for the application from the below table.
Electrical Properties
Physical Properties
Current Ratings
Nominal Diameters
Approx. Mass
Cable Ground Ducts Air Impedance Volt drop 1 sec short DI-3c Di-ic d-3c Size A (A) (A) (2km) (mViA/m) circuit (mm) (mm) (mm) (mm') rating(KA)
d-4 D2-3 D24c 3 (mm) (mm) (mm) (kg/m) (kg/km)
1.5 2.5 4 6 10 16 25 35 50 70 95 120 150 185 240 300
23 30 38 48 64 82 126 147 176 215 257 292 328 369 422 472
18 24 31 39 52 67 101 120 144 175 210 239 269 303 348 397
18 24 32 40 54 72 113 136 167 207 253 293 336
14.48 8.87 5.52 3.69 2.19 1.38 0.8749 0.6335 0.4718 0.3325 0.2460 0.2012 8691'0 0.1445 0.1220 0.1090
25.080 15.363 9.561 6.391 3.793 2.390 1.515 1.097 0.817 0.576 0.427 0.348 0.294 0.250 0.211 0.189
0.17 0.28 0.46 0.69 1.15 1.84 2.87 4.02 5.75 8.05 10.92 13.80 17.25 21.27 27.60 34.50
8.51 9.33 9.61 10.56 11.40 12.57 12.58 13.90 14.59 16.14 16.55 19.18 19.46 21.34 20.89 23.97 24.26 28.14 27.07 31.29 31.19 35.82 33.38 38.10 36.68 42.05 40.82 46.75 46.43 53.06 51.10 58.53
1.25 1.25 1.25 1.25 1.25 1.25 1.60 1.60 1.60 2.00 2.00 2.00 2.00 2.50 2.50 2.50
1.25 1.25 1.25 1.25 1.25 1.60 1.60 1.60 2.00 2.00 2.00 2.00 2.50 2.50 2.50 2.50
14.13 15.23 17.02 18.4 20.41 22.37 26.46 27.89 31.46 35.47 39.99 42.18 45.98 51.12 57.13 62.20
14.95 16.18 18.39 19.72 21.96 25.92 28.34 31.17 36.54 40.09 44.62 47.40 52.65 57.45 64.16 70.13
448 522 667 790 966 1295 1838 2215 2871 3617 4901 5720 8069 8690 10767 12950
501 597 762 910 1169 1768 2196 2732
4837 6115 7269 9250 11039 13726 16544
447 509