Stager Function Block

The Stager function block determines how many stages of turning on from a 0 to 100 percent (typically Pid error) input. The input range of 0 to 100 percent is divided evenly among the number of stages configured in MaxStages.

The first stage is activated when CmdPercent > 0 and deactivated when CmdPercent - Hyst. The general criterion for turning on stage N is: CmdPercent > (N 1)*100 % /MaxStages, as shown in the diagram below.

The following is the criterion for turning off stage N: CmdPercent (N -1) *100 %/ MaxStages -Hyst.

Figure 1: Stager Function Block

Figure 2: Stager Property Sheet

Input

Input Name

Description

In

Input load demand in percentage.

Numeric: 32-Bit Floating value -100-100. Default: Null

MaxStg

Maximum stages available to be turned on.

Numeric: 32-Bit Integer value 1-255. Default: Null

MinOn

Minimum time a stage should be turned on in Sec.

Numeric: 32-Bit Integer value 0-64799. Default: Null

MinOff

Minimum time a stage should be turned off in Sec.

Numeric: 32-Bit Integer value 0-64799. Default: Null

InterStageOn

Minimum time before the next stage can be turned on in Sec.

Numeric: 32-Bit Integer value 0-64799. Default: Null

InterStageOff

Minimum time before the next stage can be turned off in Sec.

Numeric: 32-Bit Integer value 0-64799. Default: Null.

OverrideOff

Override to turn off stages.

Numeric: Binary value 0, 1. Default: Null.

Disable

Disable function.

Numeric: Binary value 0, 1. Default: Null.

Table 1: Inputs of Stager Function

Output

Output Name

Description

Stages

The number of stages active.

Table 2: Outputs of Stager Function

Parameter

Parameter Name

Description

In Par

Input load demand in percentage.

Numeric: 32-Bit Floating value -100-100. Default: Null.

MaxStg Par

Maximum stages available to be turned on.

Numeric: 32-Bit Integer value 1-255. Default: Null.

MinOn Par

Minimum time a stage should be turned on in Sec.

Numeric: 32-Bit Integer value 0-64799. Default: Null.

MinOff Par

Minimum time a stage should be turned off in Sec.

Numeric: 32-Bit Integer value 0-64799. Default: Null.

InterStageOn Par

Minimum time before the next stage can be turned on in Sec.

Numeric: 32-Bit Integer value 0-64799. Default: Null.

InterStageOff Par

Minimum time before the next stage can be turned off in Sec.

Numeric: 32-Bit Integer value 0-64799. Default: Null.

Hysteresis

Stage off hysteresis.

Numeric: 32-Bit Floating value 0-100. Default: 0

Out Save

Master Sync Enabled : If you set it to "true" the last output will be set as output for one cycle after the controller restarts. The application can use it to return to the same state before the controller restart.

Out: To enable or disable the Out Save feature.

Table 3: Parameter of Stager Function

Figure 3: Stager Behaviour

Examples:

If In>0, stage-1 =On. If In<0 (0-Hysteresis), which is -11 stage-1= Off.

The below screenshot explains the stage-1 is ON when input is greater than 0 and goes OFF when input is less than (0-Hysteresis), which is -11.

  1. Stage 1 On = 1%
  2. Stage 1 Off = -11%

Input is 0, Stage-1 is OFF Input is 0

Figure 4: Example- Stager function Block

In > 0, Stage-1 = On

Figure 5: Example- Stager function Block

In < 0, Stage-1 = On. In= below stage-1 hysteresis level. Stage-1 = OFF

Figure 6: Example- Stager function Block

Interstage ON delay examples

In rises from 10 to 100, stages-1, 2 and 3 = ON. However, stager turns ON only stage-1 and waits for InterStage ON delay, which is set to 30 seconds and then turn ON stage-2 and then stage-3 (This lets next stage to turn ON until the set time after the previous stage is ON).

Stage-2 = ON, when interstage ON delay has expired and then stage-3.

Figure 7: Example- Stager function Block

Interstage ON delay examples

In= 100. If In suddenly goes to 10, stages-2 and 3 turns OFF. Stage-3 stager turns OFF immediately and waits for InterStage OFF delay which is set to 10 seconds and turns OFF stage-2 (This lets next stage to turn OFF until the set time after the previous stage is OFF).

Stage-2 =ON with In= 10

Figure 8: Example- Stager function Block

Stage-2 = OFF with In=10, after interstage OFF delay

Figure 9: Example- Stager function Block

Refer to General Description for general information about IRM N4 Function Blocks.