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Do not operate the generator if the windings are wet. If the generator is operated when the windings are wet, damage can occur due to insulation breakdown. |
When moisture is present or when moisture is suspected in a generator, the generator must be dried before being energized. For information on drying the generator, refer to Testing and Adjusting, "Insulation - Dry".
If the drying procedure does not restore the insulation resistance to an acceptable value, the winding should be reconditioned.
Note: For additional information, refer to Special Instruction, SEHS9124 .
The following methods can be used for drying a generator:
- Self-circulating air method
- Oven method
- Controlled current method
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Do not allow the winding temperature to exceed |
Run the engine and disconnect the generator load. running the engine will help circulate air. Operate the generator space heaters.
Place the entire generator inside a forced air drying oven for 4 hours at
| NOTICE |
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Use a forced air type oven rather than a radiant type oven. Radiant type ovens can cause localized overheating. |
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| Illustration 1 | g00614674 |
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External Power Source Circuit (1) Battery (12 VDC) (2) Rheostat (15 Ohm 25 W) (3) Exciter field (stator "L1") | |
| TOOLS NEEDED | ||
| Part Number | Tool | Quantity |
| 225-8266 | Clamp-on Ammeter (1200 A) | 1 |
| External Power Source Circuit | 1 | |
Heat can be used in order to dry the generator windings. This heat can be created by allowing a controlled current to flow through the generator. No high voltages are generated during the following procedure. Therefore, insulation breakdown will not occur.
- Make an external power source. Refer to Illustration 1.
- Disconnect F1+ from the voltage regulator. Disconnect F2- from the voltage regulator. Disconnect the generator load. Connect the generator output leads T0, T1, T2, and T3 together. Install the clamp-on ammeter to generator output lead T1.
Note: When the line current is measured on multiple lead units, measure the current in each conductor per phase. The currents can then be added.
- Refer to Illustration 1. Adjust the rheostat to the maximum resistance value. Connect the external power source to wires F1+ and F2-.
- Start the generator set. Run the generator set at idle speed.
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NOTICE Do not exceed the rated phase current that is listed on the generator nameplate. Exceeding the rated phase current will easily damage the generator windings.
- Monitor the phase current. Gradually increase the engine RPM. Increase the engine RPM until one of the following conditions are met:
- The rated phase current is obtained.
- The full generator set speed is obtained.
- If more phase current is necessary, slowly turn the rheostat. Turn the rheostat until the rated phase current is reached.
- On an hourly basis, stop the drying procedure. Check the insulation resistance. Repeat the above steps until the insulation resistance is acceptable.