SDMO R 340 U, User And Maintenance Manual

Page: 244 / 287

Installation and maintenance
R250
A.V.R.
6
LEROY-SOMER
4067 en - 2009.05 / b
2.3 - R250 A.V.R. option
Potentiometer for voltage setting, 1000 W /
0,5 W min: setting range ± 5 %.
- Remove the ST4 jumper.
For wiring up the external potentiometer;
the “earth” wires must be isolated as
well as the potentiometer terminals
(wires at the same voltage as the power).
2.4 - LAM characteristics (Load
Acceptance Module)
2.4.1 - Voltage drop
The LAM system is integrated in the A.V.R.
It is active as standard. It can be adjusted to
13% or 25%.
- Role of the «LAM» (Load Adjustment
Module):
On application of a load, the rotation speed
of the generator set decreases. When it
passes below the preset frequency
threshold, the LAM causes the voltage to
drop by approximately 13% or 25% and
consequently the amount of active load
applied is reduced by approximately 25% to
50%, until the speed reaches its rated value
again.
Hence the “LAM” can be used either to
reduce the speed variation (frequency) and
its duration for a given applied load, or to
increase the applied load possible for one
speed variation (turbo-charged engines).
To avoid voltage oscillations, the trip
threshold for the “LAM” function should be
set approximately 2 Hz below the lowest
frequency in steady state.
It is advised to use the “LAM” at 25% for load
impacts > at 70% of the genset rated power.
2.4.2 - Gradual voltage return function
During load impacts, the function helps the
genset to return to its rated speed faster
thanks to a gradual increase in voltage
according to the following principles:
- if the speed drops between 46 Hz and 50 Hz,
the rated voltage follows a fast gradient as it
is restored.
- if the speed drops below 46 Hz, since the
engine needs more help, the voltage follows
a slow gradient as it returns to the reference
value.
LAM
U
N
0
48 or 58 Hz
0,85 U
N
Voltage
U/f
50 or 60 Hz
fC fN
Voltage
ST3
0
Time
Drop N < 46 Hz
U
Drop N > 46 Hz
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