Pid Start-Up Guide - WEG CFW08 Vector inverter User Manual

DETAILED PARAMETER DESCRIPTION

6.3.5.3 PID Start-Up Guide

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NOTE!
When the PID function (P203=1) is set:
The digital input DI3 is automatically set to manual/automatic
(P265=15). Thus when DI3 is open, the manual mode is activated
and when DI3 is closed, the PID regulator starts to operate (closed
loop control - automatic mode).
If the function of this digital input (DI3) is changed, the operation of the
inverter will be always in manual mode.
If P221 or P222 is equal to 1, 4, 5, 6, 7 or 8 the E24 error mesage will
be displayed. Set P221 and P222 equal to 0 or 2 according to the
requirement.
The JOG and the FWD/REV functions are disabled. The inveter enabling
and disabling commands are defined by P229 and P230.
In the manual mode, the frequency reference is given by F*, as shown
in figure 6.1.
When the operation mode is changed from manual to automatic, P525
is automatically set to the value of P040 (at the instant immediately
before the commutation). Thus when the setpoint is defined by P525
(P221 or P222=0), the changing from manual to automatic is smooth
[there´s not occur abrupt oscillation in the frequency (speed) reference].
The analog output can be programmed to indicate the process variable
(P040) or the PID setpoint with P251=6 or 4, respectively.
Figure 6.26 shows an application example of an inverter controlling a
process in closed loop (PID regulator).
Please find below a start-up procedure for the PID regulator:
Initial Definition
1) Process - Definition of the PID action type that the process requires:
direct or reverse. The control action must be direct (P527=0)
when it is required to increase the motor speed and so also
increment the process variable. Otherwise select reverse
(P527=1).
Examples:
a) Direct: pump driven by inverter and filling a tank where the PID
regulates the tank level. To increase the level height (process
variable) the flow must be increased and consequently also the
motor speed must be increased.
b) Reverse: fan driven by an inverter to cool a cooling tower, with
the PID controlling the temperature of this tower. When it is
required to increase the tower temperature (process variable),
the cooling power must be descreased by reducing the motor
speed.
2) Feedback (process variable measurement): The feeback is always
realized via analog input AI1.
Transducer (sensor) to be used for the feedback of the control
variable: it is recommended to use a sensor with full scale
with at least 1.1 times higher than the largest value of the
process variable that shall be controlled. Example: If a pressure
control at 20bar is desired, select a sensor with a control
capacity of at least 22bar.
Signal type: set P235 and the position of the switch S1 on the
control board according to the transducer signal (4-20mA, 0-
20mA or 0-10V).