Checking and setting
31
Adjusting the overspeed setting
To protect the engine from mechanical
damage if the governor fails – which
would allow an uncontrolled increase in
engine speed – there is a facility for set-
ting a maximum speed which cannot be
exceeded.
The selected overspeed should be suffi-
ciently above the rated speed but below
the maximum speed allowed by the valve
gear.
The rated speed is 1,500 rpm for driving
alternators with a frequency of 50 Hz.
The maximum speed is 2,800 rpm.
A safety speed of 2,000 rpm can therefore
be set, for example.
Setting an overspeed of 2,000 rpm:
D Open cover on flywheel housing.
D Turn lower potentiometer (arrow) clock-
wise with a small screwdriver as far as
the stop.
D Connect lead J at control unit input to
earth. This halves the value set for the
overspeed.
D Start engine and run at 1,000 rpm.
D Turn the potentiometer slowly in the
anticlockwise direction until engine
stalls.
D Disconnect lead J from earth.
If a fault occurs in the speed governing
system, the engine is then switched off if
its speed exceeds 2,000 rpm.
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