Generator maintenance

Generator’s bearing maintenance include every 1,000 (to be checked maker instruction recommendation) operating hours check the bearing(s) for smooth, quiet operation.

Periodically inspect the unit for any buildup of contamination (dirt, oil, etc.) on the windings.

Every 2,000 operating hours or in conjunction with scheduled engine maintenance, check the DC no load excitation voltage during startup procedure.

Monitor and record insulation resistance of the windings with a proper applied voltage from mega-ohm meter.

Monitor and record ohmic resistance of the windings with a proper ohm meter.

Possible problems include:

- slot liner insulation or enamel wire insulation may be burned or damaged

- the equipment might be full of dirt, carbon dust, water or other contaminants

- connections to the actual coils may be bad

- insulation may have been used to connect the coils

Typical problems that may exist are:

- hard shorts to the motor’s core

- hard shorts between coils either within the same phase or between phases

- coils rewound with the improper gauge wire

- loose or corroded connections

- presence of foreign particles

Testing the Rotating Rectifier Assembly.

 

 

Figure 78. Diode checking and testing

 

- The flexible leads connected to each diode should be disconnected at the terminal end, and the forward and reverse resistance checked.

- The rectifier assembly is split into two plates, + and - , and the main rotor is connected across these plates.

- Each plate carries 3 diodes, the – plate carries the negative based diodes, and the + plate carries the positive based diodes.

- Care must be taken to ensure that 3 identical polarity diodes are fitted to each plate.

Testing The Surge Suppressor (Varistor)

Figure 79. Surge Suppressor (Varistor)

- The Surge Suppressor (Varistor), is a protection device, which prevents high voltage from damaging the main rectifier diodes.

- The Surge Suppressor can be tested with a Multimeter on Mohms range.

- A good Varistor should have a very high resistance, (more than 100 Mohms in either direction).

- The Main rectifier will work normally with this device removed. But should be renewed ASAP, to avoid diode failure in the event of further transient fault conditions.