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Building Technologies Division
Basic Documentation LME7...
CC1P7105en
Infrastructure & Cities Sector
27 PWM settings
29.11.2011
27.4.3 Final settings of PWM safety parameters
Note:
PWM control by the LME7... makes use of the Hall signal for feedback. This Hall
signal is used to calculate the manipulated variable of the PWM control process. To
prevent the calculation of wrong manipulated variables in the event of incorrect Hall
signals, the working range of PWM control must be restricted via parameter
675.00
/
675.01
. For that purpose, the burner is operated in special test mode
(parameter
559
).
Warning!
In the case of
burner components (PWM fan) with voltage-related behavior, it is
recommended to read out the value (current PWM signal, parameter 920) for the
prepurge phase (P30) with the minimum permissible prepurge speed close to the
undervoltage limit
, and for the ignition phases (P38, 40 and 44) with the maximum
permissible ignition speed close to the
overvoltage limit
. If this is not observed, there
is a risk of loss of safety functions.
Procedure
Select test mode (parameter
559
) and check the prepurge speed under worst-case
conditions close to the undervoltage limit, or check the ignition load speeds under
worst-case conditions close to the overvoltage limit:
Reference:
In test mode (parameter
559
, setting value = 2), the normalized PWM signal
(parameter
675.00
) for the prepurge phase or the PWM signal (parameter
675.01
) for
the ignition phase is output as a fixed value. Start the burner and check the speed, the
volumetric air flow or air pressures under these worst-case conditions by taking
appropriate measures while ensuring compliance with the relevant standards (e.g. EN
676).
Set
safety
parameter
675.00
to the value previously determined by parameter
920
in the prepurge phase (P30)
-1%
and safety parameter
675.01
to the value of
parameter
920
in the ignition phase (P38, 40 and 48)
+1%
Follow these steps
Select programming mode for the OEM
Press
A
and
F
simultaneously for <5 seconds. Display shows
CodE
Enter the OEM’s password via
,
and
/reset
. Also see chapter
Entering the
password
Display
changes
from
PArA
to
400: SEt
Press to select the next parameter group (P500...P600). Display shows
500: PArA
Press
/reset
to go to the respective group
Press or
to select parameter
559
Press
/reset
Press
or
to set the value (2 test modes)
Press
/reset
to transfer the setting value to the onboard memory
By
pressing
ESC
twice (press
and
simultaneously) you leave the
parameter setting level and return to the parameter group
Press to select the parameter group (P600...P700). Display shows
600: PArA