Properties and Tests of Enameled Wire

Enameled wire?is a main variety of winding wire, which is composed of conductor and insulating layer. After the bare wire is annealed and softened, it is painted and baked many times. However, it is not easy to produce products that meet both standard requirements and customer requirements. It is affected by factors such as raw material quality, process parameters, production equipment, and the environment. Therefore, the quality characteristics of various enameled wires are different, but they all have Mechanical properties, chemical properties, electrical properties, thermal properties four major properties.

The above properties determine whether the quality of the enameled wire is excellent, so before the enameled wire leaves the factory for sale, we, as a supplier, have to conduct a series of tests and make a test report to reassure customers. Among them, one of the most important attributes of enameled wire is its?thermal performance. The heat resistance of enameled wire includes thermal shock and softening breakdown tests. When doing thermal performance testing, we briefly introduce the thermal shock test, which reflects the ability of the sample to withstand temperature after being stretched or coiled or bent on a round bar. Place the samples in a forced-air oven and heat for 30 inches at a temperature of ±5 °C as specified in the relevant product standard. Remove from oven to test. The specimens are allowed to cool to room temperature and then inspected for cracks in the insulation with a specified magnifying glass.

After the thermal performance, the electrical properties of the enameled wire are the most concerned. The electrical properties of the enameled wire include breakdown voltage, paint film continuity, and DC resistance test. We briefly introduce the experiment of?conductor resistance. All testing should be performed at a temperature of 15°C to 40°C and a relative humidity of 25% to 75%. Samples should be preconditioned under these atmospheric conditions long enough for the wire to reach a steady state before taking measurements. Resistance is direct current. Resistance of 1 m wire at 20 °C. The method used should provide an accuracy of 0.5%. If the resistance Rt is measured at a temperature t other than 20°C, the resistance R20 at 20°C should be calculated by the following formula:

R20 = Rt/[1+ (tt?20)]

t: the actual temperature at the time of measurement, in degrees Celsius;

α: is the temperature coefficient in K-1.

In the temperature range of 15 °C to 25 °C, the temperature coefficient used should be:

– for copper: α20 = 3,96 × 10-3 K-1;

– For aluminum: α20 = 4,07 × -3 K-1.

The second is the mechanical properties of the enameled wire, including elongation, rebound angle, softness and adhesion, scratch resistance, tensile strength and other items.

1. The elongation rate reflects the plastic denaturation of the material, and it is used to examine the ductility of the enameled wire.

2. The rebound angle and softness reflect the elastic deformation of the material: it is used to evaluate the softness of the enameled wire.

Elongation and rebound angle, the quality of softness reflects the quality of copper and the annealing degree of enameled wire affects the elongation of enameled wire:

The main factors of the springback angle are (1) the quality of the wire; (2) the influence of external force; (3) the degree of annealing.

3. The toughness of the paint film includes winding and stretching, that is, the allowable stretching deformation of the paint film without breaking when the conductor is stretched and deformed.

4. The adhesion of the paint film includes: snapping off, peeling off, mainly assessing the adhesion of the paint film to the conductor.

5. The scratch resistance test of the enameled wire paint film reflects the strength of the paint film against mechanical scratches.

Finally, introduce the chemical resistance of enameled wire, including solvent resistance and direct solderability.

1. Solvent resistance means that after the general enameled wire is wound into a coil: it must go through the impregnation process, and the solvent in the impregnation varnish has different degrees of swelling on the paint film, which is even worse at higher temperatures. The chemical resistance of the enameled wire paint film is mainly determined by the characteristics of the paint film itself: under certain conditions of the paint material, the enamelling process also has a certain impact on the solvent resistance of the enameled wire.

2. The direct solderability of the enameled wire reflects the ability of the enameled wire to solder during the winding process without removing the paint film.

The main factors affecting the direct solderability are: (1) the influence of the process; (2) the influence of the paint.