What is the purpose of the small pinholes on the flat enameled wire
- 2019-05-06-

Although the pinhole on the enameled wire is small, it is fatal to the motor!

Flat enameled wire is one of the magnet wires widely used in the production of low voltage products. One of the key functional requirements of this magnet wire is the continuity of the paint film, that is, to check the number of pinholes on the paint film of a certain length. When checking the number of pinholes, use a professional paint film continuity tester. The fewer pinholes, the better the film integrity of the magnet wire.

The pinhole defect detection is based on the principle of high-voltage discharge, and touches the electromagnetic wire and the concave wheel that applies high voltage in a half-envelope. When the film thickness is insufficient or the defects of bare copper are severe, the instrument will record the number of specific defects.

The reasons for this shortcoming can basically be divided into two categories. One is the inapplicability of copper, that is, the core of the formed steel wire has more burrs, which may be caused by the raw material itself or the drawing process. Another reason may be uneven paint, impurities in the paint, the quality of the paint itself, and the dryness of the paint.

As a motor manufacturer, you should pay special attention to this function, because this shortcoming can easily lead to motor failures and severely affect the service life of the motor.

Introduction to paint film continuity test

In the past, people used voltage mercury method, Japanese salt water method, low-pressure electrolyte method and other offline detection methods to detect the continuity of paint film. These methods are not applicable to the online inspection of enameled wire in the production process.

However, the online detection system for the continuity of the enameled wire film selected by most magnet wire manufacturers at present is a non-touch detection method based on a DC high-voltage electric field sensor. The basic principle is that the DC high voltage is generated by the DC high voltage circuit and connected with the cylindrical metal conductor in the high voltage electric field sensor, and a high voltage electric field is generated in the cylindrical metal conductor. The enameled wire is driven by the take-up wheel and passes through the high-voltage electric field at high speed. When the electric field is strong enough, corona will occur on the surface of the enameled wire. If the enameled wire film has shortcomings. During the enameled wire elapsed period, the leakage current caused by partial discharge will be formed between the metal conductor-the enameled wire-the take-up wheel. After dynamically measuring the leakage current of the enameled wire, the position and severity of the defect can be accurately measured and recorded.

When using this method to detect the enameled wire, the sensor and the enameled wire are not touched during the whole process, and no rated damage will be caused to the enameled wire. It is very suitable for on-line inspection of enameled wire running at high speed on production line. In addition, the shape of the metal conductor in the high-voltage electric field sensor is similar to a cylindrical shape, and the generated electric field is basically the same in all directions. Therefore, the detection ability in all aspects is basically the same, the detection sensitivity is high, and it is not easy to cause missed detection and false detection.

Of course, the owner of the magnet wire can only use the offline detection method, that is, the paint film continuity tester. Compared with the online detector, because of the half-envelope state test, the ability to detect shortcomings is weak, but taking into account the randomness of the sampling, it can also judge whether the function of the electromagnetic wire is qualified.