MIL-HDBK-1004/5
Table A-2
Voltage Drop on a 15,000-Foot Feeder Cable (1)
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100-Ampere
Bus 3
No-Load
Volts 1.n-
0.8-power-factor
Per-Unit Volts
(36-kVA) Unit Loads (2)
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Case D1 - One
0.986
118.3
Case D2 - Two
0.973
116.8
- Three
0.956
114.7
Case D3 - Four
0.943
113.2
- Five
0.924
110.9
Case D4 - Six
0.911
109.3
- Seven
0.894
107.3
Case D5 - Eight
0.877
105.2
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(1) Voltage does not include aircraft cable effects on voltage drop.
(2) If two 100-ampere, 0.8-power-factor unit loads are supplied from
one utilization service assembly, this is equivalent to two unit loads.
Since the results of this section are comparable to those of Section
A.1, the number of loaded feeder cables of different lengths can be obtained
from Section A.1.
Figure A-13 shows the steady state conditions of the system (100-
ampere 0.8-power-factor unit load at bus 11) before a 100-ampere
0.8-power-factor unit load is applied at bus 7. The system parameters are
15,000 feet of No. 2 AWG feeder cable; 200 feet of No. 4/0 AWG service cable;
and 40 feet of No. 2 AWG aircraft cable. The series compensation is set at 12
percent. Power supplied is based on input from one 312-kVA frequency
conversion assembly generator. No transient voltages have a magnitude
significant enough to cause problems.
The transient limit is 0.68 per unit and 1.52 per unit. The steady
state value at buses 7 and 11 must be above 0.942 per unit when the per-unit
voltage is 120 volts RMS.
Figure A-14 has an initial load at bus 11 which is equivalent to two
unit-loaded utilization service assemblies with a total 200- ampere
0.8-power-factor load. A 100-ampere 0.8-power-factor unit load is stepped on
at bus 7. The results indicate no transient or steady state problems.
With load voltage compensation, each assembly percent compensation
setting should compensate for the reactance occurring between the assembly
input and the aircraft interface point. When this is done, the end voltage
will not rise above 118 volts. The steady state values in the figures of this
section have been established prior to the application of the 100-ampere
0.8-power-factor step load. The compensation is set at 12 percent.
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