Ionization (Suited For Continuous Operation); Qrb - Siemens LMV5 Series Basic Documentation

IONIZATION (suited for
continuous operation)
Note
QRB... (for intermittent
operation only)
Notes
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No-load voltage at terminal ION (X10–03, terminal 1)
Note: The ionization probe must be installed such that protection against electric shock
hazard is ensured!
Short-circuit current
Minimum detector current required
Maximum detector current
Permissible length of detector cable
(laid separately)
The greater the detector cable capacitance (cable length), the lower the voltage at the
ionizations probe and, therefore, the lower the detector current. In the case of extensive
cable lengths and high-resistance flames, it may be necessary to use low-capacitance
cables (e.g. ignition cable).
The electronic circuit is designed such that impacts of the ignition spark on the
ionization current will be largely eliminated. Nevertheless, it must be ensured that the
minimum detector current required will already be reached during the ignition phase.
If that is not the case, the connections of the ignition transformer on the primary side
must be changed and / or the location of the electrodes also.
No-load voltage at the QRB... terminal (X10–02, terminal 1)
Minimum detector current required
(with flame)
Maximum permissible detector current
(dark current with no flame)
Maximum detector current
Permissible length of QRB... detector cable
(laid separately)
A detector resistance value of RF < approx. 5 kΩ is identified as a short-circuit and, in
operation, leads to safety shutdown as if loss of flame had occurred.
Measurement of the voltage at terminal QRB... during burner operation gives a clear
indication: If voltage drops below 1 V, safety shutdown will probably occur.
For that reason, before using a highly sensitive photoresistive flame detector (QRB1B
or QRB3S), it should be checked whether such a detector is really required!
Increasing line capacitance between the QRB... terminal and mains live «L» adversely
affects the sensitivity and increases the risk of damaged flame detectors due to mains
overvoltages.
The separate laying of detector cables as specified in Data Sheet 7714 must be
observed.
For indication of flame (on the AZL5...), observe the following general rules:
The above percentage values are obtained when, for parameter «Standardize»
(standardization of flame signal), the default setting is used.
The accuracy of the display is a maximum of ± 10 %, depending on the tolerances of
the components.
It should also be noted that, for physical reasons, there is no linear relationship
between the display and the detector signal values. This is especially obvious with
ionization current supervision.
For more detailed information, refer to Data Sheet 7714.
Basic Documentation LMV51...
4 Burner control
DC 6 µA, display flame approx. 50 %
approx. DC 85 µA, display flame approx. 100 %
100 m (wire-earth 100 pF / m)
DC 30 µA, display flame 35 %
approx. DC 70 µA, display flame approx. 100 %
100 m (wire-wire 100 pF / m)
approx. U Mains
max. AC 0.5 mA
approx. DC 8 V
DC 5 µA
CC1P7550en
01.10.2003