TP-6519 8/17 61Section 5 Component Testing and Adjustment
5.9 Governor System
The governor system consists of an electromechanical
stepper motor (actuator) and a magnetic pickup. The
ADC-RES controls the governor system operation. See
Section 7, Wiring Diagrams, for the governor
connections.
5.9.1 Operation
The frequency of the alternator output is determined by
the speed of the engine. A two-pole alternator must be
driven at 3600 rpm to provide 60 Hertz. (A 50 Hz model
must be driven at 3000 rpm.) The engine speed is
maintained by an electronic governor system that
consists of a magnetic pickup and electric actuator
(stepper motor). The governor system is controller by
the generator set controller.
The magnetic pick-up, which monitors the speed of the
flywheel ring gear, provides the speed reference signal
to the controller. The controller provides regulated
power to the bidirectional stepper motor actuator, which
is linked to the carburetor throttle arm.
At cranking speed a properly adjusted pick-up should
produce a minimum of 1.75 VAC. The magnetic pick-up
air gap is factory-set to 0.5 mm (0.020 in.). Failure or
loss of the input speed signal from the magnetic pick-up
will result in erratic speed.
A setting on the ADC-RES allows adjustment of the
engine speed. See Section 5.9.3.
A gain adjustment may be required if an unstable
(hunting/surging) condition occurs. Adjusting the gain
may require readjustment of the engine speed. See
Section 5.9.3.
5.9.2 Initial Checks and Operation Test
The factory sets the electronic governor. Under normal
circumstances the electronic governor requires no
further adjustment. Verify that the governor stepper
motor moves smoothly and steadily during operation. If
the engine operates erratically check the following
connections and conditions before adjusting the
governor.
D Verify that the electrical connections are clean and
tight.
D Verify that the battery connections are clean and
tight.
D Check the magnetic pickup connections. Poor
connections may cause an erratic s ignal or an
overspeed condition. An erratic signal causes the
generator set to govern poorly but not shut down.
D Check the resistance across the magnetic pickup.
See Section 5.9.4.
D Check for dirt buildup on the magnetic pickup. Metal
filings or caked-on dirt or grease decreases the
output signal of the magnetic pickup.
D Check for a loose or worn stepper motor/throttle shaft
coupling. Replace the shaft and bushing every 500
hours of engine operation.
D Check the carburetor for dirt, grime, or
misadjustment. Check for a loose mixer assembly.
D Check the idle-adjustment screw. The screw should
not prevent the throttle plate from closing completely.
D Check the throttle linkage for any binding, dirt,
damage, or other visible problems.
D Check for electronic governor faults. The fuel shutoff
solenoid deenergizes and the generator set shuts
down under the following conditions:
D Closed throttle
D Engine overspeed
D Broken fuel shutoff solenoid lead
D Broken stepper motor leads (erratic performance)
D Failed actuator linkage (erratic performance)
5.9.3 Hunting/Surging
Often hunting/surging problems thought to be caused
by the governor are actually caused by engine or
carburetor problems. Check engine speed stability
using the following procedure before testing the
governor.
Hot engine and exhaust system.
Can cause severe injury or death.
Do not work on the generator set until
it cools.
WARNING
Servicing the exhaust system. Hot parts can cause
severe injury or death. Do not touch hot engine parts. The
engine and exhaust system components become extremely
hot during operation.
1. Open the generator set line circuit breaker.
2. Start the generator set.
3. Hold the throttle linkage steady while the engine is
running. See Figure 5-22. If the engine runs at a
steady speed with no hunting or surging when the
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