Separate Excitation; Powerboost Iiie Voltage Regulators - Kohler 5EOZ Manual

7.3 Separate Excitation

By separately exciting the generator to determine the
presence of a faulty voltage regulator, it is possible to
determine if a running fault exists in the rotor and/or
stator. A generator component that appears functional
while static (stationary) may exhibit a running open or
short circuit while dynamic (moving). Centrifugal forces
acting on the windings during rotation or insulation
breakdown as temperatures increase can cause short
circuits.
Separate Excitation Procedure
1. Disconnect all the leads from the voltage regulator.
2. Disconnect the P10 (F1, F2) connector.
3. Connect a separate excitation circuit as shown in
Figure 7-2. Connect an ammeter and a 10-amp
fuse in series with F1.
ammeter reading.
4. The approximate ammeter reading should equal
battery voltage divided by the specified exciter
resistances (cold). Disconnect the resistor leads
and determine the resistance value using an
ohmmeter. See Section 1, Specifications, for the
correct values.
Example:
12 Volts (Battery Voltage)
3.5 Ohms Exciter Resistance
+ —
9
P6
8
F1
1. Voltage regulator
2. 10-amp fuse
3. DC ammeter
4. Battery
5. Ground to generator frame
6. Exciter armature
7. Exciter field
8. 10- or 15-ohm resistor
9. P6 connector (disconnect P6 connector before separate
excitation)
Figure 7-2 Separate Excitation Connections
34 Section 7 Generator Troubleshooting
Note and record the
3.4-amp
=
Exciter Current
1
3
2
F2
7
—
5
6
4
5. Start the engine and check that the ammeter
remains stable.
indicates a shorted rotor.
reading to zero or unstable reading, suggests a
running open in the rotor. If the ammeter is stable,
continue with step 6.
6. Check for AC output across the stator leads and
compare the measured output to the values in
Section 1, Specifications.
considerably from those listed, a faulty stator, rotor,
rectifier module, or armature is the likely cause.
Note: See Section 1, Specifications, for the stator
output
generator). These specifications are based on a
battery of 12 volts. Should the battery voltage
vary, the resulting stator output values will also
vary.
If there is no generator output during normal operation
but output is available when the generator set is
separately excited, the voltage regulator is probably
inoperative.
7.4 PowerBoost IIIE Voltage
Regulators
The generator set is equipped with a PowerBoostt IIIE
voltage regulator. See Figure 7-3.
The voltage regulator monitors the output voltage to the
generator exciter field.
If the regulator's 8-amp fuse blows, the generator set will
shut down. Verify that the regulator fuse is functional
before proceeding with the test.
+
605372
Figure 7-3 PowerBoosttIIIE Voltage Regulator
An increasing meter reading
A decreasing meter
If the output varies
voltages (with separately excited
TP-598653
TP-6053 7/04