ARMY TM 9-6115-464-34
AIR FORCE TO 35C2-3-445-2
NAVY NAVFAC P-8-624-34
(r) Adjust voltage to the minimum attainable value or a value just prior to activation of the undervoltage
protection device.
(s) Record all instrument readings (after transients have subsided).
(t) Repeat steps (a) through (s) above for all other voltage connection(s).
d. Sample Calculations. Regulation (droop) is defined for the the purposes of this method as the no-land value
minus the rated load value divided by the rated load value the quantity expressed in percent.
% Regulation =
(No–Load Voltage) – (Rated-Load Voltage) x 100
(Rated–Load Voltage)
e. Results. The data sheets shall indicate the voltage regulation as a percent of rated voltage within the
specified limits at the minimum and maximum specified voltages and the regulation as a percent of rated
voltage at the extremes, the maximum and minimum voltages attainable and the actuation of the protection
devices (if applicable). Compare these results with the requirements of table 4-1.
4-14. FREQUENCY AND VOLTAGE REGULATION, STABILITY, AND TRANSIENT RESPONSE TEST
(SHORT-TERM).
a. General. The frequency regulation (sometimes referred to as droop) of a generator set is the maximum
difference between the no load value of frequency and the value at any load up to and including rated load.
This difference is expressed as a percentage of the rated frequency of the generator set. The voltage regulation
is expressed similarly except that the rms value of voltage is used.
Frequency stability describes the tendency of the frequency to remain at a constant value. Generally, the
instantaneous value of frequency is not constant but varies randomly above and below a mean value. Stability
may be described as either short-term or long–term depending upon the length of time that the frequency is
observed. Another term, bandwidth, describes the limits of these variations. Bandwidth is expressed as a
percentage of the rated frequency of the generator set. Voltage stability is described similarly.
Frequency transient response describes the reaction of the frequency to a sudden change in some
condition; such as, a load change on a generator set. This response consists of the amount of excursion
beyond the mean of the new operating band, and the recovery time. The recovery time is the interval beginning
at the point where the frequency leaves the original prescribed operating band and ending at the point where it
enters and remains within the new prescribed operating band. The amount of surge is expressed as a
percentage of the rated frequency of the generator set. The recovery time is expressed in seconds. The voltage
transient response is described similarly.
b. Apparatus. Instrumentation for measuring load conditions, field voltage and current, and ambient
temperature shall be as described and illustrated in MIL-HDBK-705. In addition, recording meter(s) for
recording voltage and frequency shall be required.
4-10
