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

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