gefran 1600P Manual De Uso página 31

The function works for single output systems (heating or cooling).
The self-tuning action calculates optimum control parameter values during process startup.
The variable (for example, temperature) must be that assumed at zero power (room temperature).
The controller supplies maximum power until an intermediate value between starting value and setpoint is reached, after which it zeros power.
PID parameters are calculated by measuring overshoot and the time needed to reach peak. When calculations are finished, the system
disables automatically and the control proceeds until the setpoint is reached.
How to activate self-tuning:
A. Activation at switch-on
1. Switch program to STOP
2. Adjust setpoint to required value
3. Enable self-tuning by setting Stun parameter to 2 (CFG menu)
4. Switch unit off
5. Make sure that temperature is approximately room temperature
6. Switch the unit on
B. Activation from keyboard
1. Make sure that M/A key is enabled for Start/Stop self-tuning function
(butt code = 4 Hrd menu)
2. Switch program to STOP
3. Adjust temperature to approximately room temperature
4. Adjust setpoint to required value
5. Press M/A key to activate self-tuning (Attention: self-tuning will be disabled if the key is pressed again).
The procedure runs automatically until finished, when the new PID parameters are stored: proportional band, integral and derivative times
calculated for the active action (heating or cooling). In case of double action (heating or cooling), parameters for the opposite action are
calculated by maintaining the initial ratio between parameters (ex.: CPb = HPb * K; where K = CPb / HPb when self-tuning starts). When
finished, the Stun code is automatically cancelled.
Notes:
• The procedure interrupts when the setpoint value is exceeded. In this case, the Stun code is not cancelled.
• It is good practice to enable one of the configurable LEDs to signal self-tuning status. By setting one of LED1, LED2, LED3 = 3 (or 19) on the
Hrd menu, the corresponding LED will be on (or flashing) when self-tuning is active.
• For the programmer model, the program is in STOP if self-tuning is activated when the unit is switched on.
PID parameters cannot be set if the self-tuning function is enabled.
The function can be one of two types: permanent or one-shot.
The first continuously measures system oscillations to find the optimum PID values to reduce such oscillations.
It does not engage if the oscillations drop below 1.0% of the proportional band.
It is interrupted if the setpoint is changed, and is automatically resumed when the setpoint stabilizes.
The calculated parameters are not stored.
If the unit is switched off, the controller reverts to the values set before self-tuning was enabled.
One-shot self-tuning is useful for calculating values around a setpoint. It produces a variation of 10% of current power at the output and
examines the effect of the overshoot over time. These parameters are stored and replace those previously set. After this disturbance, the
controller resumes control at the setpoint using the new parameters. The parameter activated in CFG is accepted only if the control power is
between 20 and 80%.
c_Pb
SP+cSPo
SP
h_Pb
+100%
Control ouput
0%
-100%
Control output with proportional action only if proportional heating band
is separated from proportional cooling band.
PV = Process Value
SP+cSPo = Cooling Setpoint
c_Pb = Proportional cooling band
In this control mode (enabled with CtrL = 14 parameter) the type of cooling has to be specified.
Cooling PID parameters are therefore calculated based on heating parameters according to the specified ratio.
(for example: c.MEd = 1 (oil), H_Pb = 10, H_dt = 1, H_It = 4 implies: C_Pb = 12,5, C_dt = 1 , C_It = 4)
We advise you to apply the following values when setting output cycle times:
Air T Cool Cycle = 10 sec.
Oil T Cool Cycle = 4 sec.
Water T Cool Cycle = 2 sec.
NB.: Cooling parameters cannot be modified in this mode.
14 • SELF-TUNING
15 • SELF-TUNING
16 • CONTROL OUTPUT
PV
time
Heating/Cooling control with relative gain
Process
Variable
S.P.
S.P. - t.a.
2
t.a.
SP
SP+cSPo
+100%
Control output
0%
-100%
Control output with proportional action only if proportional heating band
overlaps proportional cooling band
SP = Heating Setpoint
h_Pb = Proportional heating band
31
Peak
T
PV
c_Pb
h_Pb
time
Time