CG Drives & Automation 01-7491-01r0 Functional description 139
PID Activation Margin [387]
The PID activation (wake-up) margin is related to the
process reference and sets the limit when the AC drive
should wake-up/start again.
Example 1 PID control = normal (flow or
pressure control)
[321] = F (AnIn)
[322] = Bar
[310] = 20 Bar
[342] = 2 s (inactive since [386] is activated and have higher
priority)
[381]= On
[386] = 10 s
[387] = 1 Bar
The AC drive will stop/sleep when the speed (PID output) is
below or equal to Min Speed for 10 seconds. The AC drive
will activate/wake up when the “Process value” goes below
the PID Activation Margin which is related to the process
reference, i.e. goes below (20-1) Bar. See fig. 116.
Fig. 116 PID Stop/sleep with normal PID.
Example 2 PID control = inverted (tank
level control)
[321] = F (AnIn)
[322] = m
[310] = 7 m
[342] = 2 s (inactive since [386] is activated and have higher
priority)
[381]= Inverted
[386] = 30 s
[387] = 1 m
The AC drive will stop/sleep when the speed (PID output) is
below or equal to Min Speed for 30 seconds. The AC drive
will activate/wake up when the “Process value” goes above
the PID Activation Margin which is related to the process
reference, i.e. goes above (7+1) m. See fig. 117.
Fig. 117 PID Stop/sleep with inverted PID.
PID Steady State Test [388]
In application situations where the feedback can become
independent of the motor speed, this PID Steady Test
function can be used to overrule the PID operation and
force the AC drive to go in sleep mode i.e. the AC drive
automatically reduces the output speed while at the same
time ensures the process value.
Example: pressure controlled pump systems with low/no
flow operation and where the process pressure has become
independent of the pump speed, e.g. due to slowly closed
valves. By going into Sleep mode, heating of the pump and
motor will be avoided and no energy is spilled.
PID Steady state test delay.
387 PID Act Marg
Default: 0
Range: 0 –10000 in Process unit
NOTE: The margin is always a positive value.
[711] Process Value
[387]
[712] Speed
[341] Min Speed
[386]
Stop/Sleep
[310] Process Ref
Activate/Wake up
NOTE: It is important that the system has reached a
stable situation before the Steady State Test is
initiated.
388 PID Stdy Tst
Default: Off
Range: Off, 0.01–3600 s
[711] Process Value
[387]
[712] Speed
[341] Min Speed
[386]
Stop/Sleep
[310] Process Ref
Activate/Wake up
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