Generator Rewind: Detailed Maintenance Procedures for Large Power Generators

A generator rewind is an essential maintenance task that ensures the longevity and optimal performance of large power generators. This process involves replacing worn or damaged copper windings, typically due to the failure of the original winding insulation. Understanding the detailed procedures for generator rewind is crucial for engineers, maintenance technicians, and those involved in power generation. This article will provide a comprehensive guide on the steps and considerations involved in generator rewind.

Overview of the Generator Rewind Process

Moreover, the actions during a generator rewind vary slightly depending on the size of the AC generator, but the overall processes remain similar. The following steps outline the general process:

Step 1: Verify Winding Data

Before starting the rewind process, it is important to check the existing winding data. Today, this data is usually stored in a computer database. If the winding data is already available, you can skip this step. Verify the data to ensure consistency and accuracy.

Step 2: Disassemble the Generator

The next step is to remove the wiring connections and dismantle the generator. Focus on removing the wound stator from the housing. It is worth noting that the rotor is usually not rewound, making this step more straightforward.

Step 3: Identify and Fix Faults

After removing the stator, inspect the lamination stack for any faults. Document the condition to avoid repeating existing issues. Count the turns and measure the wire gauge if you do not already have this information handy.

Step 4: Strip and Clean the Stator

Next, strip the remaining stator coils out of the slots and remove varnish insulation, if present. This step is crucial for ensuring that the new windings have a clean base. Clean the stator thoroughly to remove any residues that could affect the rewinding quality.

Step 5: Rewind the Stator

The critical step is to rewind the stator with the same data and specifications as the original. This involves carefully replacing the wires in the same size and sequence they were originally built into the stator coils. This step may require specialized equipment and expertise to ensure the winding is done correctly.

Step 6: Balance and Replace Rotor Bearings

While rewinding the stator, it is recommended to balance the rotor and replace the rotor bearings. This step is particularly important for AC generators operating in rough conditions, as the transport of such units can cause bearing damage, known as Brinelling. If the units are too difficult to transport, you can replace the rotor bearings on-site using the repaired generator.

Step 7: Dip and Bake the Stator

Once the stator is rewound, it is necessary to dip it in varnish and bake it to ensure that the new windings are properly insulated and secure.

Step 8: Reassemble and Test the Generator

After the above steps, reassemble the generator and reconnect the windings. Conduct a test run to ensure that the generator is functioning optimally. If the unit is being shipped to a remote location, it is advisable to send a new bearing with the repaired generator so it can be installed on-site.

Conclusion

Generator rewind is a complex but necessary maintenance task that can significantly extend the operational lifespan of large power generators. By following the detailed procedures outlined in this article, you can ensure that your generators are maintained to the highest standards, reducing downtime and optimizing performance.