GE Ecomagination AF-600 FP Programming Manual page 165

Parameter Description
CL-94 PID Integral Time
Range:
20 [0.01 -
s 10000 s]
*
3 3
CL-95 PID Differentiation Time
Range:
0 s [0 - 10
*
s]
CL-96 PID Diff. Gain Limit
Range:
5 [1 - The differential function of a PID controller responds
*
50] to the rate of change of the feedback. As a result,
an abrupt change in the feedback can cause the
differential function to make a very large change in
the PID controller output. This parameter limits the
maximum effect that the PID controller differential
function can produce. A smaller value reduces the
maximum effect of the PID controller differential
function.
This parameter is only active when
parameter CL-95 PID Differentiation Time is not set to
OFF (0 s).
164
Function:
The integrator accumulates a contribution to
the output from the PID controller as long as
there is a deviation between the reference/
setpoint and feedback signals. The contribution
is proportional to the size of the deviation. This
ensures that the deviation (error) approaches
zero.
Quick response on any deviation is obtained
when the integral time is set to a low value.
Setting it too low, however, may cause the
control to become unstable.
The value set is the time needed for the
integrator to add the same contribution as the
proportional for a certain deviation.
If the value is set to 10000, the controller acts
as a pure proportional controller with a P-band
based on the value set in parameter CL-93 PID
Proportional Gain. When no deviation is present,
the output from the proportional controller is 0.
Function:
The differentiator monitors the rate of change of
the feedback. If the feedback is changing quickly,
it adjusts the output of the PID Controller to
reduce the rate of change of the feedback. Quick
PID Controller response is obtained when this
value is large. However, if too large of a value is
used, the frequency converter's output frequency
may become unstable.
Differentiation time is useful is situations where
extremely fast frequency converter response and
precise speed control are required. It can be
difficult to adjust this for proper system control.
Differentiation time is not commonly used in
HVAC applications. Therefore, it is best to leave
this parameter at 0 or OFF.
Function:
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