140 Functional description CG Drives & Automation 01-7491-01r0
PID Steady State Margin [389]
PID steady state margin defines a margin band around the
reference that defines “steady state operation”. During the
steady state test the PID operation is overruled and the AC
drive is decreasing the speed as long as the PID error is
within the steady state margin. If the PID error goes outside
the steady state margin the test failed and normal PID
operation continues, see example.
Example: The PID Steady Test starts when the process value
[711] is within the margin and Steady State Test Wait Delay
has expired. The PID output will decrease speed with a step
value which corresponds to the margin as long as the Process
value [711] stays within steady state margin. When Min
Speed [341] is reached the steady state test was successful
and stop/sleep is commanded if PID sleep function
[386]and [387] is activated. If the Process value [711] goes
outside the set steady state margins then the test failed and
normal PID operation will continue, see fig. 118.
Fig. 118 Steady state test.
389 PID Stdy Mar
Default: 0
Range: 0–10000 in process unit
[711] Process Value
[310] Process Ref
[387]
[712] Speed
[388]
Stop/Sleep
[389]
[389]
[341] Min Speed
[386] PID<Min Spd
Normal PID
Stop steady
Start steady
Steady state
Normal PID
test
state test
state test
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