340

First varnish dip and bake

Lower the stator and immerse it in the varnish until bubbling stops.

Raise the stator clear of the varnish and allow it to drain over the tank for about 5 minutes.

Close the cover on the varnish tank as soon as the stator is moved.

Position the stator over a shallow pan lined with paper and allow the stator to drain and air dry for 1 hour.

Immediately begin wiping the varnish from the end bell mating surfaces, the tops of the laminations inside the stator bore, and, if applicable, the bottom of the mounting feet with a lint-free cloth (dipped in xylene for solvent varnish only).

Rotate the stator periodically during the air drying process to prevent pocketing of the varnish.

Ensure that the stator is always positioned so that the bore is in the vertical position.

Place the stator in a bake oven that has been preheated to 302°F (150°C) ±10 percent and cure for 6 to 8 hours.

Always wear thermo-insulated gloves when handling heated components.

Remove the stator from the bake oven and allow it to cool to approximately 104°F (40°C).

Second dip and bake

The sling should still be in place from the first dip and bake. If not, attach a dipping harness or slings to the stator so that the stator bore will be in the vertical position with the winding connection side down.

Lift, position, and immerse the stator in the varnish as previously described.

Raise the stator from the varnish after about 1 minute.

Close the cover on the varnish tank as soon as the stator is moved.

Repeat the air drying, draining, wiping, and baking procedures previously discussed.

Place the stator in a bake oven that has been preheated to 302°F (150°C) ±10 percent and bake for 6 to 8 hours.

Remove the stator from the oven and allow the stator to cool to approximately 104°F (40°C).

Third dip and bake

The sling should still be in place from the second dip and bake. If not, attach a dipping harness or slings to the stator so that the stator bore will be in the vertical position with the winding connection side up.

Close the cover on the varnish tank as soon as the stator is moved.

Repeat all other procedures discussed for the second dip and bake.

Winding inspection

Inspect the windings. Ensure that the following conditions are met.

Solventless varnish will not be very glossy.

• Windings are clean, smooth, and glossy, with good binding and filling.
• Varnish is uniform over the entire winding surface.
• Wedges are properly in place and bonded.
• Varnish surface is not cracked.
• Varnish is not soft and tacky (improperly cured).
• Windings are not damaged.
• End bell mating surfaces, tops of laminations in the stator bore, and the bottom of mounting feet, as applicable, are free of varnish.

Take corrective action as necessary for any unsatisfactory conditions noted.