Lam Characteristics - Leroy-Somer AVR R250 Installation And Maintenance Manual

LEROY-SOMER
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
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.
Voltage
U
N
U/f
0,85 U
N
0
ST3
6
Installation and maintenance
preset frequency
Voltage
LAM
48 or 58 Hz
50 or 60 Hz
fC fN
R250
A.V.R.
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.
U
Drop N > 46 Hz
0
4067 en - 11.2006 / a
Drop N < 46 Hz
Time