Micromod RetroPAK: SLC Configuration Manual - Manual (Page 217)

Command Series Migration to MOD 30ML
Function Code 3 - Lead / Lag
Lag Function :
To select the lag function, leave S3 at its initial value (0) and enter a number for S4. The
equation then becomes:
Y = YL +
S3 * ( S1 - S1L)
S4 + DT
Y = YL +
S3 * ( S1 - S1L)
S4 + DT
Lead Function :
To select only a lead function, leave S4 at its initial value of zero and enter a number for
S3. The equation then becomes:
Y = YL +
[S3 * ( S1 - S1L)] + [DT * (S1 - YL)]
DT
Y = YL +
[S3 * ( S1 - S1L)] + [DT * (S1 - YL)]
DT
APPLICATIONS
The next figure is a simplified example of using function code 3 in boiler applications.
This
shows function code 3 used as a lag to delay decreases in airflow for a load decrease.
Figure 3 .2.
Lead Function
example
The next figure shows function code 3 used as a lead/lag to compensate for drum level
shrink and swell due to changes in steam flow.
Figure 3 .3.
Lead/Lag Function
Example
3 - 3