16
VI.KT.F2.02
© Danfoss 06/2008
DH-SMT/DK
DH-SMT/DK
VI.KT.F2.02
© Danfoss 06/2008
17
Motor prot. (motor protection)
6174
Setting range
Factory setting
OFF / 10 ... 59 m
OFF
Prevents the controller from unstable temperature control (and resulting actuator oscillations). This
can occur at very low load. The motor protection increases the lifetime of all involved components.
OFF:
Motor protection is not activated.
10 ... 59:
Motor protection is activated after the set activation delay.
Xp (proportional band)
6184
Setting range
Factory setting
1 ... 250 K
50 K
Set the proportional band. A higher value will result in a stable but slow control of the
flow temperature.
Tn (integration time constant)
6185
Setting range
Factory setting
5 ... 999 s
20 s
Set a high integration time constant to obtain a slow but stable reaction to deviations.
A low integration constant will make the controller react fast but with less stability.
M1 run (running time of the motorized control valve)
6186
Setting range
Factory setting
5 ... 250 s
15 s
‘M1 run’ is the time it takes the controlled unit to move from fully closed to fully open
position. Set the ‘M1 run’ according to the example.
How to calculate the running time of a motorized control valve
The running time of the motorized control valve is calculated using the following methods:
Seated valves
Running time = Valve stroke (mm) x actuator speed (sec. / mm)
Example:
5.0 mm x 15 sec. / mm = 75 sec.
Rotating valves
Running time = Turning degrees x actuator speed (sec. / degr.)
Example:
90 degr. x 2 sec. / degr. = 180 sec.
Nz (neutral zone)
6187
Setting range
Factory setting
1 ... 9 K
3 K
Set the acceptable flow temperature deviation.
Set the neutral zone to a high value if you can accept a high variation in flow
temperature. When the actual flow temperature is within the neutral zone, the controller
does not activate the motorized control valve.
The neutral zone is symmetrical around the desired flow temperature value, i.e. half the
value is above and half the value is below this temperature.
If you want to tune the PI regulation precisely, you can use the following
method:
• Set the ‘Tn’ (integration time constant line 6185) to its max. value (999 sec.).
• Decrease the value for the ‘Xp’ (proportional band line 6184) until the system starts
hunting with a constant amplitude (it might be necessary to force the system by setting
an extreme value).
• Find the critical time period on the temperature recording or use a stop watch.
Temp. Critical time period
Time
This time period will be characteristic for the system, and you can evaluate the settings from
this critical period.
‘Tn’ = 0.85 x critical time period
‘Xp’ = 2.2 x proportional band value in the critical time period.
If the regulation seems to be too slow, you can decrease the proportional band value by
10%.
