Pid Parameters - ABB AW400 Series Instruction Manual

5 - Contact output controller – (this menu available when option is selected - See Par. 5.2.2.5)
Frequency / Relay
Gain
Dead Zone
Cycle time
Table 7 – Contgroller Parameters
5.2.2.1

PID Parameters

Variations in controller action are obtained by adjusting of parameters associated with the control modes.
These modes of control action that are combined to adjust the controller output signal are known as
Proportional, Integral (Reset) and Derivative.
Proportional Action (PB)
Percent proportional band is the full scale though which the error signal must vary to cause full scale output
variation due only to proportional control mode response. In Proportional Action there is a comparative
relationship between the controller loop output signal magnitude and the calculated error, which is the
difference between the process variable and the set-point. To properly use the proportional action follow
these indications: if it is desired that a small percentage of deviation of the process variable causes a full
scale output, the proportional band (PB) has to be set at a small value (high gain); on the contrary if it is
required that a large percentage of deviation causes a small scale output the proportional band has to be set
to a high value (low gain). Minimum value is 2%, maximum is 500%.
Integral Action (TR)
Integral action augments proportional action to cause a controller PID loop to drive its final control element
until the deviation is completely eliminated. It produces a corrective signal proportional to the error and the
length of time the controlled variable has been different from set-point. Integral action is expressed as the
length of time in minutes required for it to produce an output change equal in magnitude to that produced by
proportional action. The set of TR has to be in the following range: 0.02 minutes/repetition for the fastest
action, 30 minutes/repetition for the slowest action.
Derivative Action (TD)
Derivative action augments proportional action by responding to the rate of change of the process variable. It
is used to make each controller PID loop more responsive to sudden process disturbances. The derivative
time in minutes is the amount of time by which the proportional action (or proportional plus integral action) is
advanced. The minimum value for derivative action is 0.01 minutes for the fastest response, and the
maximum value is 8 minutes for the slowest response.
Control Zone
This parameter is used to avoid continuous control adjustments for small fluctuation from set-point. If for
example set-point is set to 7 and CZ = 1, control action is not active in the range 6.5 –7.5.
Manual Reset
This parameter represents the integral action set manually. It is activated by setting TR parameter to "0".
Direct/Reverse action
This parameter has to be set according to the final control element: select Direct if to an output increase has
to correspond an increase in the final control element, select Reverse if to an output decrease has to
correspond a increase in the final control element and vice versa.
Span
Is the measuring range used by controller.
Output High and Low limits
38
- Function not supported at this time, leave always
the selection "Relay"
GAIN Numeric entry in %/100
Default: 1 (=100%)
DZ Numeric entry in Engineering units
Default: 0
CYCLE Numeric Entry in seconds
Default: 0 sec