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LEROY-SOMER
- LAM : action eliminated by cutting the ST5
jumper.
Voltage
ST5 disconnected
U
N
U/f
0.85 U
N
0
ST3
2.3.2 - 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 principle:
- If the speed drops between 46 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
2.4 - Typical effects of the LAM with
a diesel engine with or without a
LAM (U/F only)
2.4.1 - Voltage
Transient voltage drop
U
N
0,9
with
0,8
LAM
1 s
0
Installation and maintenance
Underspeed and LAM
Voltage
P2
LAM
48 or 57.5 Hz
50 or 60 Hz
fC
fN
Drop N ≤ 46 Hz
Time
(U/f)
without LAM
Time
2 s
3 s
R438
A.V.R.
2.4.2 - Frequency
f
N
0,9
0,8
0
2.4.3 - Power
0
2.5 - R438 A.V.R. options
- Current transformer for parallel operation
of ....../1A. 5 VA CL 1.
- Remote voltage adjustment potentiometer:
470 Ω, 0.5 W min: adjustment range ± 5%
(range
limited
potentiometer P2). Remove ST4 to connect
the poten-tiometer. (A 1 kΩ potentiometer
can also be used to extend the adjustment
range).
- R 731 external module: sensing of 3-
phase voltage 200 to 500 V, compatible with
parallel operation. Disconnect ST1 to
connect the module; set the voltage via the
module potentiometer.
- R 734 module: detection of 3-phase
current and voltage for parallel operation on
unbalanced installations (imbalance > 15%).
- R 726 module: 3 functions (mounted
externally)
P.F. regulation (2F) and voltage sensing
circuit before paralleling (3 F).
- Control through DC voltage used
monitoring apply to the terminals for
connection of a potentiometer DC voltage :
• internal impedance 1,5 kΩ
• ± 0,5V enable a voltage setting of 10%.
3971 en - 11.2006 / c
Max speed drop
1 s
2 s
Variation in the load
Load shedding due to "LAM"
1 s
2 s
by
internal
with
LAM
without
LAM
Time
3 s
LAM
Time
3 s
voltage
7
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