PART 2
AC GENERATORS
Page 48
Section 2.4
Diagnostic Tests
2. If the VOM indicated any other readings the voltage is
BAD. Refer back to the flow chart.
Note: “Residual” voltage may be defined as the voltage
produced by rotor residual magnetism alone. The amount
of voltage induced into the stator AC power windings by
residual voltage alone will be approximately 2 to 16 VAC,
depending on the characteristics of the specific Generator.
If a unit is supplying residual voltage only, either excitation
current is not reaching the rotor or the rotor windings are
open and the excitation current cannot pass. On current
units with air-cooled engines, “field boost” current flow is
available to the rotor only during engine cranking.
TEST 3 – CALIBRATE VOLTAGE
Discussion
When voltage output is too high, it is possible to adjust voltage
output of the generator. To access this menu a password
will be required to be entered into controller. Replacement
controllers do not require calibration unless output is not within
the specifications. (Refer to the Specifications section in the
front of this manual.)
Procedure
1. Set Volt-Ohm-Meter (VOM) to measure AC voltage.
2. Set up the VOM to measure output voltage on the breaker.
3. Open the Main Line Circuit Breaker (MLCB) on the
generator.
4. On the controller, press the ESC key until the main menu
is present. (Refer to the Menu Navigation found in
Section 1.10)
5. While at this screen proceed to enter the following
password:
UP, UP, ESC, DOWN, UP, ESC, UP, UP
6. After the password has been entered, proceed to the EDIT
menu.
7. Press the down arrow key until the screen indicates
CALIBRATE VOLTAGE and press ENTER.
8. After pressing enter, a value will appear on the screen.
Note: The default setting from the factory for calibration is 1024.
9. Set AUTO-OFF-MANUAL switch to the MANUAL position.
10. While the unit is running, use the UP or DOWN arrows to
adjust the calibration setting. A higher value will create a
lower voltage at the breaker and vice versa a lower value
will create a higher voltage at the breaker.
Calibration factor must NOT be adjusted below 990 or
above 1040. Adjusting outside of this window could
result in damage to the machine.
11. Once a desired output voltage has been achieved, press
ENTER to save the new setting.
Note: The Calibration Setting will reset to being a password
protected option after the controller is left idle.
Verification
While the unit is running, verify that the output voltage at
the breaker is consistent within 5 volts to what the controller
displays in the DEBUG menu under OUTPUTS. (Refer to Section
1.10 Menu Navigation).
Results
1. If during the verification process the output voltage at the
breaker and the display match and the calibration setting
was not adjusted outside of the window, stop testing.
2. If a correct voltage output was not achieved using the
window specified, refer to “Problem 1 – Test 4 Fixed
Excitation / Rotor Amp draw test.”
TEST 4 – FIXED EXCITATION TEST/ROTOR
AMP DRAW TEST
Discussion
Supplying a fixed DC current to the rotor will induce a magnetic
field in the rotor. With the generator running, this should create
a proportional voltage output from the stator windings. With the
use of the MIN/MAX feature of a Volt-Ohm-Meter (VOM), it is
possible to capture the maximum output of a particular winding
before faulting out on under-voltage.
Under-voltage Alarm – When the AUTO-OFF-MANUAL is set in
the MANUAL position the following logic is used to trigger the
alarm “under-voltage”:
•Cranking – If the starter disengages before a voltage has
developed in the stator the controller will initiate a shutdown
alarm for “under-voltage.”
Note: For further information about under-voltage shut-
downs, refer to Section 2.1 “Description and Components.”
Table 9 has been provided to record the results of the following
procedure. These results may be required when requesting
factory support. Additional copies of Table 9 can be found in
Appendix A “Supplemental Worksheets” at the back of this
manual.
Table 9. Test 4 Results Worksheet
Test Point Results
Wires 2 and 6 Voltage
VAC
Wires 11 and 44 Voltage
VAC
Static Rotor Amp Draw
Amps
Running Rotor Amp Draw
Amps
Column Identified
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