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The above
shows a mechanical - hydraulic speed sensing and electro - hydraulic load
sensing governor. The two sensing elements are independent of each other. Since
the load change is sensed prior to a speed change then the primary governing is
achieved by the load sensing element. In this respect the speed sensing element
can be considered as both a fine correction facility as well as a back up
system for the load sensing element.
The load
sensing is achieved by an electronic computing circuit which controls a
solenoid operated pilot valve in direct proportion to load changes. The
measured value may either be an electrical output from a generator or a signal
from a torque measuring circuit.
Where the
plant is set for constant load operation, e.g. CPP with shaft alternator then a
constant fuel setting is required with adjustments being made to the engine
load by a pitch shedding facility in the CPP system. The two loads are then
summated and compared to the constant load set point with the comparator output
being amplified and fed to the pitch shedding device.
A similar
system of summation and correction can be applied to any load sharing
application. Where a number of prime movers, driving either single or combinations
of loads, are involved usually one prime mover/governor is set to be the master
control with the others set as slaves. Correcting signals are then fed to the
slaves to give a predetermined load share amongst the prime movers
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