
SEBU8219-01 111
Maintenance Section
Generator Set - Test
i01473730
GeneratorSet-Test
SMCS Code: 4450-081
Personal injury or death can result from high volt-
age.
When power generation equipment must be in op-
eration to make tests and/or adjustments, high
voltage and c
urrent are present.
Improper test equipment can fail and present a
high voltage
shock hazard to its user.
Make sure the testing equipment is designed for
and correctl
y operated for high voltage and c u r-
rent tests being made.
When servici
ng or repairing electric power gener-
ation equipment:
•
Make sure th
e unit is off-line (disconnected
from utility and/or other generators power
service), and either locked out or tagged DO
NOT OPERATE
.
•
Make sure the g enerator engine is stopped.
•
Make sure all batteries are disconnected.
•
Make sure al
l capacitors are discharged.
Table 14
Tools Needed
Part Number Part Quantity
6V-7070
Digital
Multimeter
1
12 VDC battery 1
Potential
Transformer
1
The generator set functional test is a simplified test
that can be performed in order to determine if the
generator is functional. The generator set functional
test should be performed on a generator set that is
under load.
The generator set functional test determines if the
following statements happen:
•
A phase voltage is being generated.
•
The phase voltages are balanced.
•
The phase volta
ges change relative to engine
speed.
The generator
set functional test consists of the
following steps:
1. Stop the gener
ator. Connect the potential
transformer’s high voltage winding to the
generator terminals (T1) and (T2). Connect
the voltmete
r to the low voltage winding. If two
transformers are available, connect the high
voltage winding of the second transformer to the
generator te
rminals (T1) and (T3). Connect the
secondary terminals that correspond to generator
terminal (T2) of both transformers together.
2. Disconnect wires “F1+” and “F2-” from the voltage
regulator. Disconnect the generator from the load.
3. Connect a 12 VDC automotive battery to wires
“F1+” and “F2-”.
NOTICE
Do not opera
te the generator set at a speed that is
higher than one-half of the rated speed.
Higher spee
ds under these test conditions can cause
damage to the system.
4. Operate the
generator set at half the rated speed.
5. Measure the AC voltage across the low voltage
terminals o
f the transformer that correspond to the
following generator terminals: “T1” and “T2”, “T2”
and “T3”, and “T3” and “T1”. Record the voltages.
6. Monitor the voltage between any two of the
locations in step 5. Decrease the generator set
speed by 10
percent. Increase the generator set
speed by 10 percent.
7. The volta
ges that were measured in Step 5 should
be nearly equal. These voltages should measure
a minimum of 85 VAC.
8. When the generator set speed is decreased by
10 percent, the voltages that were measured in
Step6sho
uld decrease by 10 percent. When the
generator set speed is increased by 10 percent,
the voltages that were measured in Step 6 should
increas
eby10percent.