6
INSTALLATION AND MAINTENANCE
LSA 46.2 / 47.1 - 4 POLE
ALTERNATORS
TECHNICAL CHARACTERISTICS
Ref. 2981 GB - 4.33/b - 07.02
LEROY-SOMER
2.3 - Excitation system
For both the AREP & PMG excitation systems, the alternator
voltage regulator is the R 448.
With
AREP
excitation, the electronic AVR is powered by two
auxiliary windings which are independent of the voltage
detection circuit. The first winding (X1, X2) has a voltage
proportional to that of the alternator (Shunt characteristic), the
second (Z1, Z2) has a voltage in proportion with the stator
current (compound characteristic : Booster effect). The power
supply voltage is rectified and filtered before being used by
the AVR monitoring transistor. As a result the machine has a
short-circuit current capacity of 3 IN for 10 s, and good
immunity to distortions generated by the load.
With
PMG
excitation, a permanent magnet generator (PMG)
is added to the alternator. This is fitted at the rear of the
machine and connected to the AVR. The PMG supplies the
AVR with voltage which is independent of the main alternator
winding. As a result the machine has a short-circuit current
capacity of 3 IN for 10 s, and good immunity to distortions
generated by the load.
The AVR monitors and corrects the alternator output voltage
by adjusting the excitation current.
2.3.1 - R448 AVR characteristics
- shunt power supply : max 140V - 50/60 Hz
- rated overload current : 10A - 10s
- electronic protection (overload, voltage detection opening
short-circuit): excitation overload current for 10 s then return
to approximately 1A
The alternator must be stopped (or the power switched off,
see section 3.5.3.) in order to reset the protection.
- Fuse :
• F1 on X1,X2.
- voltage detection : 5 VA isolated via transformer
0-110 V terminals = 95 to 140 V
0-220 V terminals = 170 to 260 V
0-380 V terminals = 340 to 520 V
- voltage regulation ±0.5%
- normal or rapid response time via strap ST2
- voltage adjustment via potentiometer P2
other voltages via adapter transformer
- current detection : (parallel operation) :
C.T. 2.5 VA cl1, secondary 1A (Option)
- quadrature droop adjustment via potentiometer P1
- underspeed protection (U/f) and LAM : frequency threshold
adjustable via potentiometer P4
- max. excitation current adjustment via P5 : 4 to 10A
- 50/60 Hz selection via strap ST3.
2.3.2 - R 448 power supply connection
AREP excitation
ST3
50Hz
60Hz
4 x Ø5.8 x 175 x 115
200 x 140 mm
X2
X1
Z2
E+
E-
0V
110
220
380
Z1
L2(V)
L3
(W)
340-520V
170-260V
R448
P5
P2
P4
P3
ST2
ST5
R731
T.I.
ST4
Option
Option
Option
S1
S2
P1
ST1
ST6
Response time
With LAM
normal fast
Single-phase
detection
46.2
47.1
49.1
3-ph detection
Excitation
ceiling
Frequency
Under-
speed
Stability
External potentiometer
for adjusting the voltage
Voltage
Quad droop
Field
5+
6 -
Pwr supply
(see 2.3.2)
95-140V
F1
Slow fuse
250V 10 A
AREP
PMG
ST9
W/o LAM
Aux. windings
Yellow
Red
Green
Black
5 +
6 -
Exciter field
X2
Z1
X1
Z2
E+
E -
R448
