Even though governor faults cause improper prime mover operation, improper
prime mover operation can be also caused by other items such as low fuel
pressure. When the prime mover stops working properly, find out which part is
defective. Do this by:
1. Substituting, if available, a part that works for the one suspected of causing
the problem.
2. Simplifying the system. Remove options and observe performance after
each removal.
3. Testing the parts suspected of causing the problem. Follow the
manufacturer’s instructions or set up input and operating conditions which
produce known outputs.
To test the EPG, use Chapter 2 to verify that the installation is correct and
perform the installation check. Those checks are the best way to test the EPG.
The Preset Rated Speed section (under Step 6 of the Installation Checks in
Chapter 2) is the best test of the EPG’s ability to control speed. It requires the
use of a signal generator with an isolated output. If appropriate, do the checks for
Paralleled Generator Applications with the Load Sensor (referenced in Chapter 2,
manual 82313).
Other Checks
Do the installation checks described in the previous paragraph first. Then check
the following:
1. If the prime mover is stable at some speeds or power outputs but oscillates
at others, the linkage may not be compatible with the fuel control. Refer to
Linkage Compatibility under Actuator Mounting and Linkage in Chapter 2.
2. If the prime mover oscillates at low frequency (about 1 Hz) and the Gain and
Stability adjustments (in Chapter 2) are correct, then friction in the linkage
may be the cause.
· Disconnect the actuator from the fuel control.
· Manually stroke the fuel control linkage from stop to stop as if the
actuator were moving it. The linkage must move freely without friction
and without backlash. Lubricate or replace linkage or fuel control parts
as required.
3. If the prime mover is unstable only when load sharing, verify that:
· Load sensor CTs and PTs are wired correctly.
· Voltage regulator droop or cross current compensation is set correctly.
· The voltage regulator is not intermittent or otherwise faulty.
If the problem is still there, reduce the load gain a little and set the load gain
pot on all other load sensors in the system for the same load signal at full
load. It may be necessary to reduce the load signal to 3 volts in extreme
cases. Consult with your authorized Distributor or with Woodward in such
cases.
