2 Mode of Operation
HELENOS III
3
2. Mode of Operation
The actual speed of the engine is read by a pulse pick-up from a cog wheel, preferably from
the starter gear. The microprocessor (CPU) of the control unit compares the actual speed with
the preset value. If differences are stated, the new actuator signal is calculated by the CPU
and transmitted to the actuator via the output stage. Feedback from the actuator indicates the
current position of the output shaft thus allowing optimum signal adjustment by the CPU.
As the governor comprises an I-fraction and as for any load level the speed is permanently
compared with a fixed preset value, speed can be kept constant also in steady state, i.e., droop
is zero.
For applications requiring droop, the speed related to the respective fuelling is calculated by
the CPU and entered as correction of the setpoint value.
During standstill, a particular circuit ensures that only the current of the control unit is
received by the governor, but no current flows to the actuator motor.
