TM 5-6115-465-34
T0 35C2-3-446-2
NAVFAC P-8-625-34
TM06858B/06859D-34
and minimum trace excursion in the stabilized por-
of this test, At each of the following load conditions
tion. Draw two lines parallel to the axis of chart
(one step) operate the set for a minimum of 40 sec-
movement, one each passing through these maximum
onds (or the short-term stability period plus the
and minimum trace excursions respectively.
allowable recovery time as specified in the procure-
ment document). During each load condition read and
(c) Draw a line (C) parallel to and equi-
record all instrument readings except thermal instru-
distant from the edges of the observed voltage band-
mentation (for three-phase sets it is not necessary to
width. Determined in (b) above.
record line-to-line voltages). Each load condition
shall be applied to the generator set in one step at the
(d) Using the rated voltage of the gen-
end of the short-term stability period for the previous
erator and given requirements of table 7-1, calculate
load condition. The load conditions are:
the steady-state voltage bandwidth (D). Draw this
steady-state voltage bandwidth as two parallel lines,
1. Rated load
parallel to and equidistant from the median (C) at
2. No load
the observed voltage bandwidth.
3. Rated load
4. No load
(3) To determine the maximum voltage var-
5. Rated load
iation at constant load:
6. No load
7. Rated load
(a) One-half the observed voltage band-
8. No load
width (B) is the plus or minus value of voltage devia-
9. 3/4 rated load
tion at constant load.
100 No load
11. 3/4 rated load
(b) Divide each of the values obtained in
12. No load
(a) by the rated voltage of the generator and multiply
13. 3/4 rated load
by 100 to convert to percentage.
14. No load
15. 1/2 rated load
(4) To determine the maximum overshoot and
16. No load
undershoot at each load step, and express this as a
17. 1/2 rated load
percentage of its rated voltage, proceed as follows:
18. No load
19. 1/2 rated load
(a) From the meter recording charts,
200 No load
determine the maximum amount that the voltage trace
21. 1/4 rated load
goes beyond the line (3) of the observed voltage band
22. NO load
following the load change. See figure 7-1 for Illus-
23. 1/4 rated load
tration of overshoot and undershoot.
24. No load
25. 1/4 rated load
(b) Divide the result obtained in (a) by
26. No load
rated voltage (as given on the generator nameplate),
27. Rated load
then multiply by 100 to convert to percentage.
28. NO load
29. Rated load
30. No load
CAUTION
31. Rated load
32. NO load
Do not use the constant operating voltage
at each load as the divisor in the compu-
(d) Repeat (a) through (c) for all voltage
tation. Use only the rated voltage of the
connection(s) and frequency(ies).
generator.
d.
Results.
(5) To determine the time required to restore
stable voltage conditions after each load change (re-
(1) Prepare a chart giving for each load change
the momentary overshoot or undershoot and the re-
covery time):
covery time. For each constant load, give the maxi-
(a) The prescribed steady state voltage
mum voltage variation.
bandwidth, extended to the point at which the voltage
trace leaves the prescribed steady state band, shall
(2) Referring to figure 7-1 begin by determin-
be considered as the time at which the transient con-
ing the observed (B) and steady-state (D) voltage band-
ditions begin. The point at which the voltage trace
widths.
enters and remains within the prescribed band after a
load change shall be considered as the point at which
(a) Mark numerically the stabilizations
stabilization begins.
occurring after each load change, starting with the
stabilization obtained before the first load change.
(b) Measure the distance (in inches) on
the chart from the point where the voltage trace leaves
(b) Determine the observed voltage band-
the prescribed steady state band to the point where
width (B) by marking the maximum trace excursion
7-9
