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Shipboard Electrical Power Systems
book

Shipboard Electrical Power Systems

by Mukund R. Patel
December 2011
Intermediate to advanced content levelIntermediate to advanced
370 pages
12h 24m
English
CRC Press
Content preview from Shipboard Electrical Power Systems
Power Distribution 199
SOLUTION
Letter code G motor draws 5.6 to 6.3 kVA/hp on starting as per Table5.3. Therefore,
the worst-case starting current is 6.3 × 100 × 1000 ÷ (3 × 460) = 791 A at θ =
cos
–1
0.35 = 69.5° lagging. The phase voltage at the source is 480 ÷ 3 = 277.1 V.
Using exact Equation (3.13), the voltage at motor terminals is
277.1∠ 0° – 791 –69.5° × (0.01 + j 0.02) = 259.4∠ 0.2° V/ph
Voltage drop magnitude = (277.1 – 259.4) = 17.7 V/ph
% V
drop
= (17.7 ÷ 277.1) × 100 = 6.39 %.
By approximate Equation (3.15), V
drop
= 791 (0.01 × 0.35 + 0.02 × 0.937) =
17.6 V/ph, a close match with the exact value of 17.7 V.
By approximate Equation (8. ...
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Publisher Resources

ISBN: 9781439828175