Motor slot in the electric field distribution and high frequency (overvoltage) transformer winding on the voltage distribution is very similar. When the notch is not made corona treatment, the end of the leakage charge is mostly concentrated in the capacitance near the notch, so the electric field is more concentrated, so it is easy to produce corona. The use of constant resistivity or non-linear resistivity corona layer as well as the inner screen corona layer can make the slot at the electric field uniformity, to prevent the end of the corona.
End insulation surface using silicon carbide corona layer, the use of which can automatically adjust the resistivity with the external application of the field strength characteristics, so that the voltage distribution is uniform. When the use of internal screen corona layer, is wrapped in the coil insulation to a certain number of layers, it is wrapped with a semiconductor layer, the first layer of semiconductor layer is the longest, and then gradually shorten. This can form a semiconductor shield similar to capacitive casing. This method is very stable and reliable for improving the distribution of electric field. However, because of the complex structure and high cost, it is only used in high-voltage generators with particularly large capacity.
Epoxy powder mica insulated coils used in the anti-scorch paint, generally used in epoxy polyester paint to add the appropriate amount of carbon black, graphite or silicon carbide and other conductive materials formulated. Paint in the conductive material easy to precipitate, use must be stirred evenly.
Semiconductor paint is generally applied by hand with a brush, according to the coil corona structure and requirements. For the main insulation has been cured molding, if the first level of constant resistance corona structure, the linear part of the first brush low-resistance semiconductor paint, and then flat pack a layer of alkali-free glass cloth or asbestos tape. After wrapping, brush another layer of low-resistance semiconductor paint, so that the glass cloth or asbestos tape is penetrated, and dry at room temperature. End and then brush the semiconductor paint in resistance, two semiconductor paint must be in accordance with the provisions of a good lap, and then half stacked package of a layer of glass cloth tape, and then brush the semiconductor paint in resistance 2 times, to be dry with a special electrode to check the surface resistance of the coil.
The use of a molding halo process, in the package after the main insulating layer, first in the straight part of the half-stacked package of a layer of low-resistance semiconductor tape, and then at the end of the half-stacked package of two layers of medium-resistance semiconductor tape, two kinds of semiconductor tape in accordance with the provisions of the good lap. Semiconductor tape package, a layer of polyester film, and then hot press molding.
The use of internal screen corona structure, must strictly ensure that its position and feet in accordance with the provisions of the time. The end of the beveled edge gap to ensure that the working voltage does not corona, corona-resistant conformal materials can be used to fill the gap between the fixed parts. Conformable materials available at room temperature or high temperature curing adhesive, high temperature curing adhesive, need to bake heating curing.
