IfyouwanttotunethePIregulationprecisely,youcanusethefollowingmethod:
•Setthe‘Tn’(integrationtimeconstant)toitsmax.value(999sec.).
•Decreasethevalueforthe‘Xp’(proportionalband)untilthesystemstartshunting(i.e.getsunstable)withaconstantamplitude(it
mightbenecessarytoforcethesystembysettinganextremelowvalue).
•Findthecriticaltimeperiodonthetemperaturerecorderoruseastopwatch.
Temp.
Criticaltimeperiod
Time
Thiscriticaltimeperiodwillbecharacteristicforthesystem,andyoucanevaluatethesettingsfromthiscriticalperiod.
‘Tn’=
0.85xcriticaltimeperiod
‘Xp’=
2.2xproportionalbandvalueinthecriticaltimeperiod
Iftheregulationseemstobetooslow,youcandecreasetheproportionalbandvalueby10%.Makesurethereisaconsumption
whenyousettheparameters.
VI.GU.L2.02
©Danfoss|2017.09|139
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