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The harm and inspection of pinholes on enameled wire

source:未知   time:2024-09-23 10:20nbsp;  click:

Enameled wire is the most widely used electromagnetic wire in the production of low-voltage products. A key performance requirement of this electromagnetic wire is the continuity of the paint film, that is, to check the number of pinholes in the paint film under a certain length. When checking the number of pinholes, a professional paint film continuity tester is used. The fewer the number of pinholes, the better the integrity of the paint film of the electromagnetic wire.
The detection of pinhole defects adopts the principle of high-pressure discharge flow, and the electromagnetic wire is contacted with the concave wheel with high pressure in a semi-enveloping manner. When the paint film thickness is insufficient or there are serious bare copper defects, the instrument will record the specific number of defects.
 
The causes of this defect can basically be attributed to two categories. One is the unsuitability of copper materials, that is, the molded wire core has more burrs, which may be caused by the raw materials themselves or the wire drawing process; the other reason may be uneven painting, impurities in the paint, the quality of the paint itself, and drying after painting.
 
As a motor manufacturer, special attention should be paid to this performance, because this defect can easily lead to inter-turn faults in the motor, seriously affecting the service life of the motor.
Introduction to online detection of paint film continuity Paint film continuity detection used to use some offline detection methods, such as voltage mercury method, Japanese salt water method, low-voltage electrolyte method, etc., which are not suitable for online detection of enameled wire in the production process. The online detection system for enameled wire film continuity currently used by most electromagnetic wire manufacturers is a non-contact detection method based on DC high-voltage electric field sensor. Its basic principle is to generate DC high voltage through a DC high-voltage circuit and connect it to a cylindrical metal conductor in the high-voltage electric field sensor, so that a high-voltage electric field is generated inside the cylindrical metal conductor. Driven by the take-up wheel, the enameled wire passes through the high-voltage electric field at high speed. When the electric field strength is large enough, corona is generated on the surface of the enameled wire. If the enameled wire with defects in the paint film passes through it, a leakage current caused by partial discharge will be formed between the metal conductor-enameled wire-take-up wheel. By dynamically measuring the changes in the leakage current of the enameled wire, the defect location and severity of the enameled wire can be accurately measured and recorded.
When this method is used for detection, the enameled wire and the sensor part are not in contact during the whole process, so there will be no additional damage to the enameled wire, which is very suitable for online detection of enameled wire running at high speed on the production line. In addition, the metal conductor in the high-voltage electric field sensor is approximately cylindrical, and the electric field generated is basically the same in all directions, so the detection capability in all directions is basically the same, the detection sensitivity is high, and it is not easy to miss or misdetect.

Of course, users of electromagnetic wires can only use offline testing, that is, using a paint film continuity tester. Compared with online detection testers, because it is only a semi-envelope state test, the ability to detect defects is slightly weaker, but given the randomness of sampling, it can basically qualitatively determine the performance compliance of the electromagnetic wire.
low voltage electric motor, Ex motor, Motor manufacturers in China, three phase induction motor, Wolong Nanyang Explosion Protection
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