Fuel / Air Ratio Control (Farc); General; Program Sequence; Standby - Siemens LMV5 Series Basic Documentation

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Fuel / air ratio control (FARC)

5.1 General

The electronic fuel / air ratio control system LMV51... can control up to 4 actuators, the
LMV52... up to 6 actuators. The functions of the dampers are ready assigned to the
addresses and are defined as follows:
LMV51...
1 Air damper
2 Fuel 1 (gas)
3 Fuel 2 (oil)
Auxiliary actuator 1 (mixing device) ¹)
4
5
6
7
¹)
VSD (LMV51.2...)
²)
Actuators used in connection with air control (can be parameterized)
Actuators 1...6 are controlled with a resolution of 0.1°. They can be adjusted between
0° and 90°. The VSD is controlled with a resolution of 0.1 %. It can be adjusted
between 0 % (off, prepurge / postpurge fan speed) or 10 % (ignition and operating
speeds) and 100 %.

5.1.1 Program sequence

The program phases are controlled by the burner control. They advance in tune with
the fuel / air ratio control system.
In standby, the actuators are driven to their home positions. A deviation from the
required position does not lead to lockout, but only to start prevention. The home
position is defined for all actuators and can be adjusted differently for oil and gas.
Parameters:
HomePosAir
HomePosGas
HomePosOil
HomePosAux
Aux2
Aux3
VSD
In Phase 24, the actuators used for the control of air (air actuator and auxiliary actuator)
are driven to their postpurge positions. If the actuator does not reach the required
position within the maximum time, safety shutdown will take place → position check.
The prepurge time starts only when the actuators have reached their prepurge
positions. The prepurge position is only defined for the actuators used for the control of
air and can be parameterized depending on the type of fuel. The fuel actuators
maintain their home positions.
Parameters:
PrepurgePosAir
PrepurgePosAux
Aux2
Aux3
VSD
Basic Documentation LMV51...
5 Fuel / air ratio control (FARC)
LMV52...
Air damper ²)
Fuel 1 (gas)
Fuel 2 (oil)
Auxiliary actuator 1 (mixing device) ²)
Auxiliary actuator 2 ²)
Auxiliary actuator 3 (FGR) ²)
VSD ²)
LMV51... LMV52...
x x
x x
x x
x x
x
x
x
LMV51... LMV52...
x x
x x
x
x
x
CC1P7550en
01.10.2003