Section 5 Component Testing And Adjustment; Introduction; Theory Of Operation - Kohler Power Systems 8RESV Service Manual

5.1 Introduction

The procedures in this section cover the testing and
adjustment of components on the generator set. Use
these procedures in conjunction to the troubleshooting
in Section 4 to verify that components function properly
and to locate the source of problems.
Note: Some procedures may require the disassembly
of the enclosure or alternator to access the
components. See Section 6 for disassembly
procedures.

5.2 Theory of Operation

The generator set utilizes a rotating-field alternator to
produce AC voltage. See Figure 5-1. Refer to Section 7
for the complete generator set schematics.
When the controller receives a start signal, it energizes
leads FP and 71. FP energizes the rotor field and lead
71 energizes the crank relay P10. The field current
generates a magnetic field that produces AC voltage
when it rotates. The controller monitors this AC voltage
to determine the engine speed. When the controller
senses cranking speed, run relay P11 is energized and
the engine is permitted to start. When the engine speed
reaches 1000 RPM for the 8RESV or 750 RPM for the
10/12RESV, the alternator produces sufficient voltage
to self-excite. The controller drops power to lead 71,
ending the start sequence.
step-by-step engine start sequence.)
When self-excited, the alternator field is energized by
voltage produced in the auxiliary windings, which are
designed solely to provide current to the alternator field.
This current is controlled by the generator controller to
maintain output voltage at the generator's rated level
(more field current is required as the load on the
generator increases).
Note: The controller does not excite the field during the
warmup or cooldown portion of the cycle
exercise. The field is also disabled during
cooldown and fault cooldown (occurs after
certain faults prior to shutting down).
The controller monitors the generator output voltage
through leads 11 and 44. It receives a speed signal and
power for exciting the field from the auxiliary windings
55 and 66 and supplies current to the alternator field
through outputs FP and FN.
TP-6881 7/15

Section 5 Component Testing and Adjustment

(See Section 4 for a
Controller
1
55F
8
7
6
1. Circuit breaker
2. Power lead (55)
3. Excitation to rotor
4. Brushes
Figure 5-1 Single-Phase Generator Schematic
Section 5 Component Testing and Adjustment
2
3
4
5
TP6907
5. Slip rings
6. Main field (rotor)
7. Stator windings
8. Sensing leads (11--44)
75