Compatible — LEROY-SOMER

For these models: LSA 42.2, LSA 42.2 S4 J6/4.

Procedure

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 field wires (5+) and (6-). Assembly B : Connect a “Variac” variable power supply and a diode bridge on both exciter field wires (5+) and (6-). Both these systems should have characteristics which are compatible with the alternator field excitation power (see the nameplate).
3. Run the unit at its rated speed.
4. Gradually increase the exciter field 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 Anode Cathode ~ ~ ~ + - 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 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 13 Installation and maintenance LSA 42.2 - 2 & 4 POLE ALTERNATORS 3433 en - 2010.10 / g LEROY-SOMER

Source: manual:3433_en.pdf. Figures and steps are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.