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Enameled wire manufacturers: pinholes can be fatal to motors

Enameled wire is a low-voltage production in the application of Z widely used electromagnetic wire. One of the key performance requirements of this electromagnetic wire is the continuity of the enamel film, that is, to check the number of pinholes in the enamel film of a given length. The number of pinholes is checked using a professional varnish continuity tester. The lower the number of pinholes, the better the integrity of the electromagnetic circuit varnish.

Pinhole defects are detected using the high-voltage discharge method. The electromagnetic wire is in semi-envelope contact with the high-voltage concave wheel. When the film thickness is insufficient or there are severe bare copper defects, the instrument will record the exact number of defects.

The causes of this defect can be basically divided into two categories. One is improper copper material, i.e., more burrs in the plastic wire core, which may be caused by the raw material itself or the drawing process; another reason may be uneven paint, impurities in the paint, bad quality of the paint itself, dry paint, etc.

As a motor manufacturer, special attention should be paid to this performance, because this defect can easily lead to inter-turn failure of the motor and seriously affect the service life of the motor.

Continuous inspection of the paint film has been used some off-line inspection methods, such as voltage mercury method, Japanese brine method, low-pressure electrolyte method, etc., which is not suitable for the online inspection of the enameled wire during the production process.

The current continuous online inspection system for enameled wire coating used by most electromagnetic wire manufacturers is a non-contact detection method based on DC high-voltage electric field sensors. Its basic principle is through the generation of DC high voltage DC high voltage circuit and high-voltage electric field sensor, a cylindrical metal conductor cylindrical high-voltage electric field generated by the metal conductor this wheel drive, enameled wire high-speed through the high-voltage electric field, when the electric field strength is large enough, the surface of the enameled wire corona, the enameled wire through the paint film defects, the metal conductor - enameled wire -receiving wheel will form between the partial discharge generated by the leakage current. By dynamically measuring the change in the leakage current of the enameled wire, the location and severity of the defect in the enameled wire can be accurately measured and recorded.

When using this method for inspection, the enameled wire is not in contact with the sensor section during the entire process, so there is no additional damage to the enameled wire, making it ideal for online inspection of enameled wires traveling at high speeds on production lines. In addition, the metal conductor in the high-voltage electric field sensor is approximately cylindrical, and the generated electric field is essentially the same in all directions. Therefore, the detection capability in each direction is basically the same, and the detection sensitivity is high, so it is not easy to miss or mis-detect.

Of course, the user can only use offline detection of electromagnetic lines, that is, the paint film continuity tester, compared with online detection instruments, because only half of the envelope state detection, the ability to find defects is slightly weaker, but taking into account the randomness of sampling, but also to determine the performance of electromagnetic lines in line with.