What is the use of small pinholes on flat enameled wires
- 2021-02-25-

Although the pinhole on the enameled wire is small, the motor is lost!

Flat enameled wire is one of the magnet wires widely used in the production of low voltage products. One of the important functional requirements of this magnet wire is the continuity of the paint film, that is, to check the number of pinholes on a certain length of paint film. 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 inspection is based on the principle of high-voltage discharge, contacting the electromagnetic wire with the half-envelope of the concave wheel that applies high voltage. When the film thickness is lacking or the defect of bare copper is serious, the instrument will record the number of specific defects.

The reasons for this shortcoming can be basically 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 monotony of the paint.

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

Introduction to paint film continuity test

In the past, people used off-line inspection methods such as the voltage mercury method, the Japanese salt water method, and the low-pressure electrolyte method to check the continuity of the paint film. These methods are not suitable for online inspection of enameled wire in the production process.

However, the online inspection system for the continuity of the enameled wire film selected by most magnet wire manufacturers is a non-contact inspection 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 is 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 passage of the enameled wire, the leakage current caused by partial discharge will be formed between the metal conductor, the enameled wire and the take-up wheel. By 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 check the enameled wire, the sensor and the enameled wire are not in contact during the whole process, and no rated damage will be caused to the enameled wire. It is more suitable for online inspection of enameled wire working at high speed on the 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 electric field generated is basically the same in all directions. Therefore, the inspection ability of all aspects is basically the same, and the inspection 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 inspection method, that is, the paint film continuity tester. Compared with the online inspection instrument, due to the semi-envelope condition test, the ability to inspect the shortcomings is weaker, but considering the randomness of the sampling, it can also judge whether the function of the electromagnetic wire is qualified.