TP-6519 8/17 49Section 5 Component Testing and Adjustment
Section 5 Component Testing and Adjustment
5.1 Theory of Operation
The generator set utilizes a rotating-field alternator to
produce AC voltage. Upon activation of the generator
master switch, DC current from the battery magnetizes
the rotor (field). When the magnetized rotor rotates
within the s tator windings, an electrical voltage
develops within the stator. As engine speed and
generator output increase, the SCR module feeds
rectified stator output current to the rotor through the
brushes/slip rings to increase the strength of the rotor
field. As the rotor field increases in strength, generator
output also increases. The ADC-RES c ontroller
monitors the generator output voltage through leads 11
and 44 (single-phase) or leads V7, V8, and V9
(three-phase) and adjusts the DC current from the SCR
module to the rotor to meet load requirements. See
Figure 5-1.
FP
11
34
55
21
44
7
5
2
8
6
TP6196
1. Fuse
2. Power lead (55)
3. Excitation to rotor
4. Brushes
5. Slip rings
6. Main field (rotor)
7. Stator windings
8. Sensing leads (11--44)
66
11
1
ADC-RES
SCR
4
(-- )
(+)
AC1
AC2
G1
G2
44
66
66
55
55
G
F+
FN
FP
FN
3
Figure 5-1 Single-Phase Generator Schematic
5.2 Separate Excitation
To determine the cause of no or low AC output, refer to
the troubleshooting flowchart in Figure 5-2. Before
beginning the test procedures, read all safety
precautions at the beginning of this manual. Many of the
test procedures include additional safety precautions.
Check the condition of the alternator fuse before
performing the separate excitation procedure. The
inline fuse is located in lead 55 on the c ontroller. See
Figure 5-1. If the fuse is not blown, use the following
procedure to separately excite the generator using an
external voltage source (a 12-volt automotive battery).
Separately exciting the generator can identify faulty
voltage regulation by the ADC controller or reveal a
running fault in the rotor and/or stator. An external
power source duplicates the role of the voltage regulator
and excites the generator field (rotor). A generator
component that appears to be in good condition while
stationary may exhibit a running open or short circuit
while moving. Centrifugal forces acting on the windings
during rotation cause a broken circuit to open, or
increasing temperatures cause the insulation to break
down, resulting in a running fault. If this test shows that
the rotor and stator are in good condition, test the
voltage regulation using the tests in Section 5.7.
No Generator Output
Separate Excitation
Output within
Specifications
Check Rotor
Check Wiring, Fuses,
SCR Module and
Controller
Check Stator
TP563273
Erratic or No Output
Figure 5-2 Generator Troubleshooting
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