P-9-TM-457-35
T . O . 35C2-3-442-2
TM-07464A-35
TM 5-6115-457-34
c. If generator set is equipped with an
FREQUENCY ADJUSTMENT
10-14,
AC output receptacle box, check phase
RANGE TEST.
sequence of each receptacle for proper
rotation.
Perform the frequency adjustment
range test as follows:
10-13. PHASE BALANCE TEST.
PRECISE GENERATOR SETS.
a.
Perform the phase balance test as
follows :
1. Operate generator set at full load.
a. Operate generator set at 240/416
2. Slowly adjust frequency from 58 to
volts, rated speed and no load. Adjust
62 hertz (for 50/60 hertz operation) and
voltage as necessary until average voltage
390 to 420 hertz (for 400 hertz operation).
is 240 volts line to neutral. Measure each
Clockwise rotation shall increase frequency.
line to neutral voltage to the nearest0O.1 volt
Voltage shall remain at rated value through-
at load terminals and record.
out the frequency range. The frequency
rheostat shall allow frequency adjust over
NOTE
the following ranges at any load:
50 hertz operation - Between 48 and 52
Load must be balanced. Record all
hertz but not below
three line to neutral voltages and
45 hertz.
obtain the average value. Reduce
or raise voltage as required, by
60 hertz operation - Between 58 and 62
the amount that the previously
hertz but not above
computed average differs from
65 hertz.
rated voltage. The average of the
400 hertz operation - Between 390 and 420
three phase voltages should be
hertz but not below
equal to rated voltage.
370 hertz or above
430 hertz,
b. Measure and record each of the line
to neutral voltages.
b. UTILITY GENERATOR SETS.
c . The maximum difference in the three
line-to-neutral voltage under all balanced
1. Operate generator set at full
loads at rated voltage and speed shall not
exceed one percent rated voltage and speed
speed by adjusting manual speed control.
shall not exceed one percent rated line-to-
Record frequency.
neutral voltage. That is, no phase voltage
shall differ from the average by more than
2. Turn manual speed control knob
1.2 volts.
90 degrees. Record frequency. A 90 degree
turn of the manual speed control knob shall
d. Formula to compute percentage of
not cause a change in frequency greater
voltage unbalance is as follows:
than 1 percent.
100 x maximum deviation from average
3. Repeat step 2. a number of
+ (T3-N)
( T 1 - N ) + 3 (T2-N)
times, both raising and lowering frequency.
10-5
