Chapter 6 - Parameter Description
6-5
SET PID Limit-L
27 30.00 Hz
SET PID Limit-H
28 60.00 Hz
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The Unit Format
parameter has selection
for 0.1 or 0.01. In order to provide more accurate
control if transducer range is low or set point
should have two decimals, select 0.01 format.
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Set the maximum
feedback unit value
based on transducer range. Example: for transducer
0-250PSI change the parameter SET-25 to 250PSI.
This parameter provides proper scaling of an analog
feedback signal to transducer range.
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Determine and set
the set point value for
the PID control in parameter SET-26. This setting
should be within the transducer range.
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The VFD PID control has High and Low limit
settings for output frequency. When PID calculated
output frequency is less than Low limit or higher
than High limit, the VFD output will stay at
frequency limit. The minimum recommended low
limit frequency is 20Hz which should be sufficient
to provide adequate air flow for motor cooling. If
sleep mode is enabled for pump application, the
PID Low limit should be set 1Hz or more above no-
demand VFD frequency. This will provide more
stable sleep mode operation.
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The
P-Gain
determines how much
the output frequency will be changed depending on
the process error (difference between Feedback
value and Set point). Basically, it changes the
system sensitivity. If P-Gain is set too high, the
system becomes unstable and PID will create a
frequency output oscillation. The default settings
for P-Gain are different for different applications to
provide optimal and stable control.
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The
I-Time
determines how much
of the process error will be accumulated and used
as an additional offset to the PID output frequency.
If I-Time setting is low, the PID output will be
calculated based on a present error only so the
system will be more responsive to any change of
the feedback signal and will be less likely to
overshoot set point. If I-Time and P-Gain values are
set too high, the system can overshoot the set point
and create an oscillation (unstable control).
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The PID control
can be set to Direct or
Inverse type. If feedback is below set point, Direct
PID will increase and Inverse PID will decrease the
output frequency.
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When SET-32 parameter value is changed from
0Hz to any frequency value, sleep mode parameters
SET-33~35 become available. The Sleep frequency
should always be 1Hz or more higher than SET-27
PID Low limit. When there is no demand in the
system, the VFD will decrease speed below Sleep
Frequency to PID Low limit and after SET-33 time
delay will go to sleep mode and stop based on SET-
16 setting if SET-34 Sleep Boost set to 0PSI. Refer
to page 7-2 for Sleep Mode operation diagram.
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If SET-34 is set to
0.0 [Unit], the sleep
boost mode is disabled. If SET-34 is enabled and
there is no demand in the system the VFD will
decrease speed below Sleep Frequency to PID Low
limit and, after SET-33 time delay, will go to sleep
boost mode to increase system pressure by SET-34
value before VFD switches to sleep mode and
stops. In order to increase system pressure above
set point, the PID control is disabled and VFD
ramps up to FG2-11 Dwell Frequency, which
SET Unit Format
22 0.1
SET F/B Unit Max
25 100.0PSI
SET PID SetPoint
26 50.0PSI
SET PID P Gain
26 10.0%
SET PID I Time
26 1.0 sec
SET Out Inverse
26 No
SET Sleep Freq
32 35.00 Hz
SET Sleep Delay
33 20 sec
SET Sleep Boost
34 2.0 PSI
Summary of Contents for CI-007-P2
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Page 110: ...Chapter 6 Parameter Description 7 4 PID control with Pipe Broken function diagram...
Page 111: ...Chapter 6 Parameter Description 7 4 7 5 PID control with Pre PID function diagram...
Page 112: ...Chapter 6 Parameter Description 7 5 7 6 PID Control Setting Notes...
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