TM 9-6115-604-34
NAVFAC P-8-633-34
(4)
Adjust a regulated phase voltage (line-to-neutral) to rated voltage.
(5)
Read and record the generator frequency, and all line to neutral voltages.
(6)
Compute the voltage unbalance (VU) for each voltage and frequency test using the following formula:
V MAX-V MIN
VU (L-N)=
X 100
V RATED
d.
Results. The maximum voltage unbalance in the three line-to-neutral voltages shall not exceed 1 percent of the
rated line to neutral voltage.
12-22. REGULATOR RANGE
a.
General. The voltage adjust device, associated with the voltage regulator provided with the generator set, must
have an adjustment capable of varying the regulated voltage throughout the limits, and under the various load
conditions and temperature ranges without causing the voltage droop of the set to exceed specification limits.
The voltage adjust device must also be capable of providing an operating voltage other than rated voltage for
special types of equipment, and to compensate for external line drop.
b.
Apparatus. Instrumentation or measuring load conditions, ambient temperature, and the generator field (or
exciter field) voltage and current shall be as illustrated in Figure 12-5.
c.
Procedure.
(1)
Preparation for test.
(a)
Connect the load and field instrumentation in accordance with Figure 12-5, for one voltage and
frequency.
(2)
Test
(a)
Start and operate the generator set. Allow the set to stabilize at rated load, rated voltage, and rated
frequency (60 Hz). During this period record all instrument readings, including thermal instrumentation, at minimum A
intervals of 10 minutes. If necessary, adjustments to the load, voltage, and frequency may be made to maintain rated
load at rated voltage and frequency. Adjustments to the voltage and frequency shall be limited to those adjustments
available to the operator: specifically, adjustments to the voltage or frequency adjust devices. When utilizing the droop-
type speed control system as the prime speed control, the speed and droop portions of the control may be adjusted. No
other adjustments to the voltage and frequency control systems shall be made. Adjustments to the load, voltage, or
frequency controls shall be recorded on the data sheet at the time of adjustment. Stabilization shall be considered to
have occurred when four consecutive voltage and current readings of the generator (or exciter) field either remain
unchanged, or have only minor variations about an equilibrium condition with no evident continued increase or decrease
in value after the last adjustment to the load, voltage, or frequency has been made.
(b)
No further adjustments shall be made to any set control for the remainder of this test except the
control panel voltage adjust device.
(c)
Record all instrument readings.
(d)
Remove load.
(e)
Record all instrument readings (after transients have subsided).
(f)
Adjust the terminal voltage to the maximum specified value of 4575 V, line-to-line.
(g)
Record all instrument readings.
CAUTION
At voltages above rated values, the generator will be supplying less than rated current; at
voltages below rated values, the generator will be supplying greater than rated current. To
avoid damage to Instrumentatlon and load banks do not by-pass the voltage and current
protection devices.
12-28
