Settings And Mode Of Operation - Siemens LMV37.4 Series Basic Documentation

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Building Technologies
12.15.1

Settings and mode of operation

The maximum trimming range of -15
linked to the 4...20 mA specification of the analogue input (40% trimming range based
on 16 mA  1% trim per 0.4 mA).

20 mA = +25% speed correction

10 mA = 0% or no speed correction

4 mA = -15% speed correction
Figure 87: Setting range trim limits
In order to adapt to the application and the environmental conditions present at the time
the settings are made, the trim range can be restricted independently for each fuel (the
setting 0% deactivates the relevant direction of influence). It is also possible to set a wait
time for trim function activation, e.g. to obtain more reliable residual oxygen content
values for O2 trimming. The wait time during operation can be practically deactivated by
selecting an extremely low value if the trim function is used as temperature
compensation.
To influence altered environmental conditions in the ignition and to improve the ignition
behavior, the ignition speed can also be adapted depending on the ambient temperature
where necessary. The temperature-dependent offset on the ignition speed specified in
the prepurging is retained until the delay time has elapsed in operation.
Impact of the trimming with different outputs
It is unlikely that an identical trim correction (e.g. +10% speed) will have the same
impacts for low-fire and high-fire. This is why load-dependent trim damping is used. The
damping factor is based on low-fire and can be set in the value range 0% (no damping)
to 100% (no trimming with low-fire). The damping is interpolated linearly to the low-fire
based on the current (limited) trim correction value. The output-dependent impact of the
trim correction can already be taken into account by the external control in the current
setting.
Note!
The impact of the trimming is changed very slowly with 0.1% per 0.2 seconds. This
means that it takes 50 seconds to deactivate the trim function starting from +25%.
Basic documentation LMV37.4...
12 Fan control
...
+25% cannot be changed and is intrinsically
20 mA = +25% (theoretical maximum trim value)
+20% Upper trim limit (parameter 548 / 568)
10 mA (no trim)
-4% Lower trim limit (parameter 547 / 567)
4 mA = -15% (theoretical minimum trim value)
CC1P7546en
17.12.2018