Woodward 2301E, Инструкция по установке и эксплуатации, Страница: 42 / 182

2301E Digital Control Manual 26641
32 Woodward
Maximum Fuel Function
The Maximum Fuel Function is a software-adjustable maximum fuel limit on the
fuel demand. It is used to set a maximum position of the actuator. This is
generally used to prevent engine overloading or other situations where the
maximum fuel delivered to the engine should be limited. The function can be
disabled by adjusting the Max Fuel Limit to 100%. The maximum fuel limiter is
disabled in systems configured for reverse acting actuator.
Start Fuel Limit Function
The Start Fuel Limit Function provides a limit to the fuel demand which prevents
over-fuel conditions during starting of the engine (Figure 3-2). During start-up,
when engine speed exceeds the MPU fail speed, the Start Limit Function is
momentarily triggered to immediately limit the fuel demand to a software-
adjustable start fuel limit. The start ramp begins increasing the fuel demand at a
software-adjustable rate shortly after the start fuel limit is triggered. The rate can
be set at zero to eliminate the ramp function. When engine speed reaches 95%
of the speed reference, and the PID is in control of the fuel demand for 1 second,
the Start Limit Function will immediately increase to a maximum value of 100%.
When engine speed decreases below 5% of rated speed from a shutdown, the
Start Fuel Limit Function is disabled and re-armed for trigger during the next
start. The start fuel limit function also works on reverse-acting systems. The
function can be disabled by adjusting the Start Fuel Limit to a value of 100.
Figure 3-2. Start Limit Function
The Dual Start Fuel Limit with Ramp Function provides secondary limiter typically
used on slow speed engines. (Figure 3-2). During start-up, when engine speed
exceeds the MPU fail speed, the Start Limit Function is momentarily triggered to
immediately limit the fuel demand to a software-adjustable start fuel limit. When
engine speed reaches the second breakpoint the Start Limit Function will
immediately decrease (or increase) to a different fuel demand level. When
engine speed reaches 95% of the speed reference, and the PID is in control of
the fuel demand for 1 second, the Start Limit Function will immediately increase
to a maximum value of 100%. The Dual Start Fuel Limit Function is disabled and
re-armed for trigger during the next start.