Hobart Brothers 6910, Operation And Maintenance Manual With Illustrated Parts List

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(4) Adjustment and Test of Controller and Actuator (Series 6910C Generator Sets with
Speed Control PC Board)
Refer to Figure 7. The controller has three control potentiometers used to control the IDLE speed:
the GAIN potentiometer, the DROOP potentiometer, and the potentiometer marked “I”. In addi-
tion, a SPEED control potentiometer is located just next to the GAIN potentiometer. The new
speed control board is used to adjust RPM’s at the RATED speed setting. Make controller set-
tings as follows:
(a) Preliminary Controller Settings
•
With the engine OFF, set the “I” adjustment at the FOURTH increment mark from zero.
•
Set the GAIN adjustment at the THIRD increment mark from zero.
•
Set DROOP adjustment COUNTERCLCKWISE to minimum (zero) position.
•
Turn the adjustment pot on the speed control board, all the way COUNTERCLOCKWISE.
Then, turn the pot twelve full turns CLOCKWISE.
•
Start the engine, leave at IDLE and adjust the controller’s SPEED potentiometer until the
engine is operating at 875 RPM or an output frequency of 175Hz. Turning the adjustment
CLOCKWISE increases engine RPM and turning it COUNTERCLOCKWISE decreases en-
gine RPM.
(b) Checking No-Load Operation of Controller
•
Turn the GAIN potentiometer control slowly CLOCKWISE until the governor becomes un-
stable and the actuator lever oscillates. (If the actuator lever DOES NOT oscillate at this
setting, upset the lever manually to cause it to oscillate).
•
Next, turn the same GAIN potentiometer control slowly COUNTERCLOCKWISE until the
governor becomes stable and the oscillations cease.
•
Turn the “I” potentiometer control slowly CLOCKWISE until the governor again becomes
unstable and the actuator lever oscillates.
•
If the governor DOES NOT become unstable and the lever DOES NOT oscillate, place “I”
potentiometer control setting at approximately EIGHT increment marks from zero (or TWO
increment marks from maximum setting).
•
If the governor DOES become unstable, and the actuator lever DOES oscillate, turn the “I”
potentiometer control slowly COUNTERCLOCKWISE until the governor becomes stable
and the oscillations cease.
•
Flip the engine MODE switch to the BUILD-UP VOLTAGE position. Let the engine stabi-
lize, then flip the switch back to IDLE. Engine speed should stabilize within 3 to 5 diminish-
ing oscilllations. If it doesn’t, repeat the first three steps above.
NOTE: For more accurate and dependable settings, when making GAIN and “I” adjustments, ALWAYS
adjust GAIN before adjusting “I” and upset the throttle lever in between adjustments.
NOTE: If engine speed STILL doesn’t stabilize, recheck governor linkage. If linkage is set properly, the
governor controller is probably defective.
2-3 May 1/91 Revised
Page 16
OM-2028