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Page Title:
Adjusted system capacity calculation |
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|  MIL-E-7016F
L= Primary system load requirement, including the input to
the secondary system with the existing load.
M = Secondary system load requirement
6.3.5 Adjusted system capacity calculation. The wide deviations in
the characteristics and usage of system components necessitate the development of
individual rating procedures for each system configuration with due consideration of
the effects of installation and environment. Sample calculations are given in Figures
7 and 12, and below. These are not necessarily typical but illustrate the method
used.
a.
Electromagnetic rating factor. Lacking more specific
information it is reasonably safe to assume that the maxi-
mum load capacity of the generator is 100 Percent of the
normal rating at minimum rated speed, increases as a
straightline function to 200 percent at 1-1/2 times minimum
rated speed and remains constant at 200 percent from
1-1/2 times minimum rated speed to 2 times rated speed.
For a generator with nominal speed range of 4000-8000 rpm,
the maximum rating at 5500 rpm will be: 1. 00 + 1500/2000
= 1.75 x nominal rating. This factor replaces the nominal
5-second rating factor of 2.00; when converted to a direct-
multiplying factor the 5-second electromagnetic factor
becomes 1.75/2 = 0.87. For the 5-minute and contin-
uous ratings, the electromagnetic rating factor is assumed
to remain 1.0.
b.
Rating factor for paralleling. This factor iS arbitrarily
set at 0.9 of the interval system capacity. Deviation from
this value requires the approval of the procuring actitity.
Thermal rating factor. This rating is based on the rate of
C.
flow of cooling medium through the generator. It is
assumed that the specific heat capacity of the generator is
utilized when the 5-second interval rating is determined,
and that environmental effects of temperature altitude, and
differential pressure have no appreciable effect over the
5-second interval, Therefore, this factor is 1.0. For the
5-minute and continuous ratings, rating curves shall be used
for the specific generators in the particular application.
Analysis of motor and other starting transients. The magnitide
6.3.6
of system overloads due to motor and other starting transient power requirements
may be determined as follows:
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