7
INSTALLATION AND MAINTENANCE
LSA 46.2 / 47.1 - 4 POLE
ALTERNATORS
TECHNICAL CHARACTERISTICS
Ref. 2981 GB - 4.33/b - 07.02
LEROY-SOMER
PMG excitation
2.3.3 - Frequency compared with voltage
(without LAM)
2.3.4 - LAM characteristics
The LAM system is integrated in the regulator, as standard it
is active (ST5 with bridge). It can be deactivated by removing
the ST5 bridge.
- 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 15% and consequently the amount of active
load applied is reduced by approximately 25%, 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 engine).
To avoid voltage oscillations, the trip threshold for the LAM
function should be set approximately 2 Hz below the lowest
frequency in steady state.
2.3.5 - R 448 AVR options
- Current transformer for parallel operation
of....../1 A -2.5 VA CL 1 (See the diagram included with this
manual).
- Remote voltage adjustment potentiometer :
470
Ω
, 3 W min. : adjustment range ± 5% (range limited by
internal voltage potentiometer P2). Remove ST4 to connect
the potentiometer. (A 1 k
Ω
potentiometer can also be used to
extend the adjustment range by ± 10%)
- R 731 module
: detection of 3-phase voltage 200 to 500V,
compatible with parallel operation. Cut ST1 to connect the
module; set the voltage via the module potentiometer.
- R 726 module
: regulation system changed to “4-function”
(See the maintenance manual and connection diagram).
• PF regulation (2F)
• equalization of voltages before paralleling (3 F).
• possibility of coupling alternators, already running in
parallel, to the mains (4F).
R 726 module connected in place of ST4.
PMG
5 +
14
15
16
6 -
X2
Z1
X1
Z2
E+
E -
R448
100 %
50 Hz
60 Hz
Hz
50 Hz
48 Hz
57.5 Hz
60 Hz
Voltage
Bend
U/U
N
Frequency
LAM
U
N
0
48 or 57.5 Hz
0.85 U
N
Voltage
U/f
50 or 60 Hz
fC
fN
Voltage
ST5 disconnected
ST3
P2
P4
Underspeed and LAM
- P4 trip threshold
for LAM or U/F
factory preset.
U
N
0
0.9
0.8
(U/f)
LAM
0.9
0.8
1 s
2 s
3 s
Time
(s)
f
N
LAM
Typical effects of the "LAM" with a diesel engine -
LAM
with LAM without LAM (U/F only)
Transient voltage drop
Max. speed drop
Variation in the load
Load on the
shaft (kW)
Voltage
Frequency
Power
Load shedding due to "LAM"
