14
INSTALLATION AND MAINTENANCE
LSA 47.2 - 4 POLES
ALTERNATORS
INSTALLATION
3742 en - 04.2003 / a
LEROY-SOMER
f) Turn the stability potentiometer P3 anti-clockwise to 2
marks away from the central position.
g) Start the engine and set its speed to a frequency of 48 Hz
for 50 Hz, or 58 for 60 Hz.
h) Set the output voltage to the desired value using P2.
- Rated voltage UN for solo operation (eg. 400 V)
- Or UN + 2 to 4% for parallel operation with C.T. (eg. 410 V -)
If the voltage oscillates, use P3 to make adjustments (try both
directions) observing the voltage between E+ and E- (approx.
10V D.C.). The best response times are obtained at the limit
of the instability. If no stable position can be obtained, try
disconnecting or replacing the ST2 jumper (normal/fast).
i) Check LAM operation: ST5 closed.
j) Turn potentiometer P4 slowly anti-clockwise until there is a
significant voltage drop (approximately 15%)
k) Vary the frequency (speed) around 48 or 58 Hz according
to the operating frequency, and check the change in voltage
from that observed previously (approximately 15%).
l) Readjust the speed of the unit to its rated no-load value.
Adjustments in parallel operation
Before any intervention on the alternator, make
sure that the speed droop is identical for all
engines.
m) Preset for parallel operation (with C.T. connected to S1,
S2 on connector J2)
- Potentiometer P1 (quadrature droop) in centre position.
Apply the rated load (cos Ø= 0.8 inductive).
The voltage should drop by 2 to 3%. If it increases, swap the
2 incoming wires of the C.T. secondary.
n) The no-load voltages should be identical for all the
alternators intended to run in parallel.
- Couple the machines in parallel
- By adjusting the speed, try to obtain 0 KW
power exchange.
- By altering the voltage setting P2 or Rhe on one of the
machines, try to cancel (or minimise) the current circulating
between the machines.
From now on, do not touch the voltage settings.
o) Apply the available load (the setting is only correct if a
reactive load is available)
- By altering the speed, match the KW (or divide the rated
power of the units proportionally)
- By altering the quadrature droop potentiometer P1, match or
divide the currents.
3.5.3 - Max. excitation setting (excitation
ceiling)
Adjustment of the current limit
via potentiometer P5 (fuse rating: 8A-10 seconds).
The maximum factory setting corresponds to that of the
excitation current required to obtain a 3-phase short-circuit
current of approximately 3 IN at 50 Hz for industrial power,
unless otherwise specified(*).
A static method can be used to reduce this value or adapt the
Isc to the actual operating power (derated machine), which is
safer for the alternator and the installation. Disconnect power
supply wires X1,X2 and Z1,Z2 and the voltage reference (0-
110V-220V-380V) from the alternator.
Connect the mains power supply (200-240V) as indicated
(X1,X2). Install a 10A D.C. ammeter in series with the exciter
field. Turn P5 fully anti-clockwise and activate the power
supply. If there is no output current from the AVR, turn
potentiometer P2 (voltage) clockwise until the ammeter
indicates a stable current. Switch the power supply off, then
on again, turn P5 clockwise until the required max. current is
obtained (no more than 10 A).
Checking the internal protection:
Open switch (D): the excitation current should increase to its
preset ceiling, remain at that level for ≥10 seconds and then
drop to < 1A.
To reset, switch off the power supply by opening switch (A).
Note: After setting the excitation ceiling as described, adjust
the voltage again (see section 3.5.2.) via P2.
(*): In some countries it is a legal requirement to have a short-
circuit current, so as to offer discriminating protection.
WARNING
depending on the mains frequency
Max. excitation
Voltage
Field ~ 10 ohms
X2
Z1
X1
Z2
E+
E-
0V
110 V
220V
380V
50Hz 60Hz
P2
P3
P4
P5
ST3
15A DC
R 448
ST4
A+
-
A
D
