U/F And Lam Functions; Typical Effects Of The Lam With A Diesel Engine With Or Without A Lam (U/F Only) - SDMO R 340 U User And Maintenance Manual

LEROY-SOMER
3.3 - U/F and LAM function
3.3.1 - Frequency variation compared
with voltage (without LAM)
Bend
Voltage
48 Hz
100 %
U/U
50 Hz
N
3.3.2 - LAM (Load Acceptance Module)
characteristics
3.3.2.1 - Voltage drop
The LAM system is integrated in the AVR. As
standard it is active.
Role of the LAM:
On application of a load, the genset rotation
speed decreases. When it falls below the
preset frequency threshold, the LAM causes
the voltage to drop proportionately to the
frequency (LAM1) or to the active power
(LAM2) depending the the rotating switch
position. This reduces the active load scale
applied until the speed returns to its rated
value.
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 engine).
To avoid voltage oscillations, the trip
threshold for the LAM function should be set
approximately 2 Hz below the rated
frequency.
Voltage
U
N
U/f
0,85 U
N
0
ST3
12
Installation and maintenance
57.5 Hz
60 Hz
Frequency
50 Hz 60 Hz
Hz
Voltage
LAM
48 or 58 Hz
50 or 60 Hz
fC fN
R 450
AVRs
3.3.2.2 - Soft voltage recovery function
During load impacts, the function helps the
genset to return to its rated speed faster with
a gradual increase in voltage according to
the principle:
- If the speed drops between 46 and 50 Hz
(in 50Hz operation), the rated voltage is
recovered by following a fast gradient.
- 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
3.4 - Typical effects of the LAM with
a diesel engine with or without a
LAM (U/F only)
3.4.1 - Voltage
Transient voltage drop
U
N
0,9
0,8
0
3.4.2 - Frequency
f
N
0,9
0,8
0
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4531 en - 2012.03 / e
Drop N 46 Hz
with
LAM
1 s 2 s
Max. speed drop
without
LAM
1 s 2 s
Time
(U/f)
without LAM
Time
3 s
with
LAM
Time
3 s