Generac 86640 - Manual (Page 22)

Test 3- Check Load Watts and Amperes
(Continued)
NOTE; The best way to check load wattage and amperage
la to use a load bank. A load bank will allow the operator
to apply a known wattage/amperage load to the generator
and win permit voltage, frequency and amperage to be
read directly from the load bank.
RESULTS;
1. If the generator Is overloaded, reduce the load to the unit’s
rated capacity.
a. If voltage and frequency are excessively low at the unit’s
rated capacity or less, go on to Test 4.
b. If voltage and frequency are acceptable at the unit’s
rated capacity, discontinue tests.
2. If the load Is within the unit’s rated capacity, but load
voltage and frequency are excessively low, go on to Test 4.
Test 4- Check Engine Power
DISCUSSION:
If excessive rpm and frequency droop occurs when
electrical loads are applied, the engine may be underpowered
due to a malfunction.
PROCEDURE:
Check the engine for (a) adequate air flow, (b) clogged
air cleaner, (c) incorrect timing, (d) mechanical failure, etc.
RESULTS:
1. If engine problems are found, repair the engine as neces­
sary.
2. If engine checks good, go on to Test 5.
Test 5- Check & Adjust Engine Governor
DISCUSSION:
If engine speed (and frequency) droop excessively under
load, the engine governor may require adjustment
PROCEDURE:
Refer to Part 7, "ENGINESPEED CONTROL SYSTEM-.
Governor adjustment procedures for both the mechanical and
electronic type governors can be found in Part 7.
RESULTS:
1. It, after governor adjustment, voltage and frequency output
at no-load and under load are good, discontinue tests.
2. If, after governor adjustment, frequency Is good, but volt­
age is excessively low, go on to Test 6.
Test 6- Do a Fixed Excitation Test
DISCUSSION:
See "CONSTANTEXCITATION TEST on Page 1.4-2.
PROCEDURE:
’TEST" on Page 1.4-2.
RESULTS:
1. If voltage is excessively low, go to Test 7.
2. If about 1/2 rated volts is indicated, go to Test 12.
Test 7- Check Wires 1 and 4
DISCUSSION:
the fixed or constant excitation test (Test 6) consisted
of applying battery direct current to the Rotor windings (12
volts DC). With the normal excitation circuit disconnected,
application of battery current should result In approximately
one-half rated voltage output (about 60-80 volts AC).
If batteiy current is applied and AC output voltage te
excessively low, a problem exists in Wires 1 and 4 from the
Regulator, or the brushes and slip rings, or the Rotor or stator
windings.
If the application of battery current results in an AC output
of about one-half rated volts, but AC output voltage is low
during normal operation, a problem exists in the stator exci­
tation (DPE) windings, in the excitation circuit between the
stator DPE windings and the Regulator, or in the Regulator
itself.
PROCEDURE:
1. Visually inspect Wires 1 and 4, between the Voltage
Regulator and the brushes.
2. Use a VOM to test Wire 1 (between the brushes and
Regulator) for continuity.
3. Check Wire 4 (between the brushes and Regulator) for
continuity.
4. Check that Wires No. 1 and 4 are properly connected at
the Regulator and at the brushes.
RESULTS:
1. Repair, replace or reconnect wires 1 and 4 as necessary.
2. If Wires 1 and 4 are good, go to Test 8.
Test 8- Check Rotor
DISCUSSION:
Problems will be encountered if the Rotor Is (a) open, (b)
shorted, or (c) grounded. This test will determine If any of
these problems exist in the Rotor.
PROCEDURE:
1. If Rotor Is installed, remove the bearing carrier cover to
gain access to the Rotor brushes and slip rings.
2. Disconnedct Wires 1 and 4 from the brushes, to prevent
Interaction.
3. Connect the positive test lead of an ohmmeter to the
positive slip ring, the common test lead to the negative slip
ring. The positive slip ring Is the one nearest the Rotor bearing
(see Figure 28). The meter should indicate the resistance of
the Rotor windings, approximately 8.5 ohms (plus or minus
10%) for both 8 and 10 kW models.
4. Set a VOM to a very high resistance scale, such as
■Rxl 0,000" or "RxlK". Zero the meter. Connect the positive
VOM test lead to the positive slip ring. Connect the negative
VOM test lead to a clean frame ground, such as the Rotor
shaft. The meter should read "infinity".
RESULTS:
1. In Step 3, a very high resistance or "infinity" Indicates an
open or partially open condition. Replace the Rotor.
2. In Step 3, a very low resistance indicates a shorted or
groundea condition. Replace the Rotor.
3. In Step 4, any reading other than "infinity" Indicates a
groundea condition. Replace the Rotor.
4. If all Rotor readings are good, go to Test 9.
Page 1.6-2