SDMO R33C3 - Page 208

12
INSTALLATION AND MAINTENANCE
LSA 42.2 - 2 & 4 POLE
ALTERNATORS
3433 en - 2010.10 / g
LEROY-SOMER
4.5.1 - Checking the winding
You can check the winding insulation by performing a high
voltage test. In this case, you must disconnect all AVR wires.
Damage caused to the AVR in such conditions is not
covered by our warranty.
4.5.2 - Checking the diode bridge
4.5.3 - Checking the windings and rotating
diodes using separate excitation
During this procedure, make sure that the alternator
is disconnected from any external load and inspect
the terminal box to check that the connections are
fully tightened.
1) Stop the unit, disconnect and isolate the AVR wires.
2) There are two ways of creating an assembly with separate
excitation.
Assembly A : Connect a 12 V battery in series with a rheostat
of approximately 50 ohms - 300 W and a diode on both eld
wires (5+) and (6-).
Assembly B : Connect a “Variac” variable power supply and a
diode bridge on both exciter eld wires (5+) and (6-).
Both these systems should have characteristics which are
compatible with the alternator eld excitation power (see the
nameplate).
3) Run the unit at its rated speed.
4) Gradually increase the exciter eld current by adjusting the
rheostat or the variac and measure the output voltages on L1-
L2 - L3, checking the excitation voltage and current at no load
(see the alternator nameplate or ask for the factory test
report).
When the output voltage is at its rated value and balanced
within 1 % for the rated excitation level, the alternator is in good
working order. The fault therefore comes from the AVR or its
associated wiring (ie. sensing, auxiliary windings).
WARNING
- -
C C C
A A A
~ ~ ~
+
C C C
A A A
+
~ ~ ~
C
A
A n o d e C a t h o d e
~
~
~
+
-
ou
A diode in good working order must allow the current
to flow from the anode to the cathode.
6 – 5 +
1A diode
12 V battery
Rh. 50 Ω - 300 W
-
+
ASSEMBLY A
Exciter field
6 – 5 +
1A diode
12 V battery
Rh. 50 Ω - 300 W
-
+
ASSEMBLY A
Exciter field
1A diode
-
+
6 –
5 +
Variac
AC
220 V
DC
12 V
50
60
70
80
90
100
40
30
20
10
0
ASSEMBLY B
Exciter field
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