ARMY TM 9-6115-464-34
AIR FORCE TO 35C2-445-2
NAVY NAVFAC P-8-624-34
(3) To determine the maximum voltage variation at constant load:
(a) One-half the observed voltage bandwidth (B) is the plus or minus value of voltage deviation at
constant load.
(b) Divide each of the values obtained in (a) by the rated voltage of the generator and multiply by 100
to convert to percentage.
(4) To determine the maximum overshoot and undershoot at each load step, and express this as a
percentage of its rated voltage, proceed as follows:
(a) From the meter recording charts, determine the maximum amount that the voltage trace goes
beyond the line (3) of the observed voltage band following the load change. See figure 4-1 for
illustration of overshoot and undershoot.
(b) Divide the result obtained in (a) by rated voltage (as given on the generator nameplate), then
multiply by 100 to convert to percentage.
CAUTION
Do not use the constant operating voltage at each load as the divisor in the
computation. Use only the rated voltage of the generator. Failure to observe this
caution could result in damage to the equipment.
(5) To determine the time required to restore stable voltage conditions after each load change (recovery
time):
(a) The prescribed steady state voltage bandwidth, extended to the point at which the voltage trace
leaves the prescribed steady state band, shall be considered as the time at which the transient
conditions begin. The point at which the voltage trace enters and remains within the prescribed
band after a load change shall be considered as the point at which stabilization begins.
(b) Measure the distance (in inches) on the chart from the point where the voltage trace leaves the
prescribed steady state band to the point where it re-enters and remains within the prescribed
voltage band for the next load condition.
(c) Divide this distance by the chart speed (in inches per second). This will give the voltage recovery
time, in seconds.
(6) Determine the voltage regulation for all load changes (e. g. rated load to no load, 1/2 rated load to no
load to 1/4 load, etc.) as follows:
(a) Using the indicating voltmeter readings subtract the load value of voltage from the no load value for
each load change (e. g. step (a) to step (b)). (For voltage regulators utilizing single-phase voltage
sensing, the value of voltage in the sensed phase only shall be used in the above calculations. For
voltage regulators utilizing multi-phase voltage sensing the average value of the sensed voltage
shall be used.)
4-13
