TUBE AS 2984568 - Caterpillar

Flashing With Engine Stopped (Static Flashing)
With the engine stopped, disconnect exciter field (L3) wires; (F1) from terminal (F1) and (F2) from terminal (F2). Connect the positive "+" cable of the six volt source to wire (F1). Put the negative "-" cable from the source and wire (F2) together for a moment, (two or three times). DO NOT HOLD THEM TOGETHER FOR MORE THAN ONE OR TWO SECONDS. According to theory, this method has the effect of putting residual magnetism back in the exciter field.A more practical method is to flash the field with the engine running. This is dynamic flashing.The Effect Of, And Testing For Moisture In SR-4 Generator Windings
Moisture can cause severe problems in electrical generators. It can lead to costly generator repairs. This section gives information on how to check for the effects of moisture on generators and how to help prevent moisture from damaging the generator.Effects Of Moisture On Windings
If moisture is allowed to remain in contact with an electrical winding, some of the moisture will eventually be absorbed. This will lower the resistance of the winding insulation. The insulation used on the windings of Caterpillar generators is moisture resistant, but constant exposure to moisture will gradually lower the insulation's resistance.Dirt can make the problem worse because it can hold the moisture in contact with the insulation. Salt (from sea air) can also make the problem much worse. This is because salt tends to absorb moisture from the air. When the salt and moisture combine, they make a good electrical conductor.If moisture has caused the main stator winding (L5) to have a low resistance to ground, current can flow from the main stator winding to ground when the generator is operated. Because of the high voltage between this winding and ground, the current flow could become high enough to cause additional break down of the insulation and damage the winding. Generator down time and significant repair cost can be the result of insulation breakdown.If moisture has caused the exciter field winding (L2) to have a low resistance to ground, a current can flow from the exciter winding to ground. The voltage between this winding and ground is much less than between the main stator winding (L5) and ground, so an insulation breakdown is not likely to occur. But an electrolysis process can cause copper to be eroded from the winding until the winding becomes an open circuit.Rotor windings are not as sensitive to moisture as the main stator winding or the exciter field winding. This is because the rotor is electrically isolated from ground and much lower voltages are involved.Generators should be stored in a clean, dry area with minimal ambient temperature variation. Ambient temperature variation can cause condensation to form moisture on the generator windings. One method to stop condensation is to use space heaters or similar devices to heat the inside of the stored generator. Before a generator that has been stored is put into service, perform a megohmmeter test on the main