LSA 42.3 — AVR wires.

For the LSA 42.3.

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 exciter field wires (5+) and (6-). 6 - 5 + 1A diode 12V battery Rh. 50 -300W - + ASSEMBLY A Field 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 field excitation power of the machine (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 machine 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 machine is in good working order. The fault therefore comes from the AVR or its associated wiring (ie. sensing, auxiliary windings). 1A diode - + 6 - 5 + Variac AC 220V DC 12V 50 60 70 80 90 100 40 30 20 10 0 ASSEMBLY B Field • Checking the diode bridge A diode in good working order should allow the current to flow only in the anode-to- cathode direction. +R +R + - -W -W IN IN IN IN Anode Cathode
5. 4.8 - Table of characteristics Table of average values: Alternator - 4 pole - 50 Hz/60 Hz - Winding no. 6 (12-wire) and M or M1 (4-wire) connected in dedicated single-phase (400 V for the excitation values). The voltage and current values are given for no-load operation and operation at rated load with separate field excitation. All values are given to ± 10% (for exact values, consult the test report) and are subject to change without prior warning. For 60 Hz operation, the resistance values are the same and the excitation current “i exc” is approximately 5 to 10% weaker. • Three-phase: 4-pole, SHUNT excitation Resistances at 20 °C (Ω) Type L/N stator Rotor Field coil Armature VS1

Source: manual:MANUAL-LEROY-SOMER-GENERATOR-LSA-42-3VS2-3-PHASE.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.