Introduction to the Heat Shock of Enamelled Wire

The heat shock performance of enameled wire is an important indicator, especially for motors and components or windings with temperature rise requirements, which has great significance. It directly affects the design and use of electrical equipment. The temperature of electrical equipment is limited by the enameled wires and other insulation materials used. If enameled wires with high heat shock and matching materials can be used, greater power can be obtained without changing the structure, or the external size can be reduced, weight can be reduced, and the consumption of non-ferrous metals and other materials can be reduced while maintaining the power unchanged.

1. Thermal aging test

It takes six months to one year (UL test) to determine the thermal performance of enameled wire using the thermal life assessment method. The aging test lacks simulation in application, but controlling the quality of paint and the degree of baking of paint film during the production process still has practical significance. Factors affecting aging performance:

The entire process from paint making to baking of enameled wire into a film, and then to the aging and decay of the paint film, is the process of polymer polymerization, growth, and cracking and decay. In paint making, the initial polymer is generally synthesized, and the coating initial polymer is cross-linked into a high polymer, which also undergoes a thermal decomposition reaction. Aging is the continuation of baking. Due to crosslinking and cracking reactions, the performance of polymers decreases.

Under certain furnace temperature conditions, the change in vehicle speed directly affects the evaporation of paint on the wire and the baking time. Proper vehicle speed range can ensure qualified thermal aging performance.

High or low furnace temperature will affect thermal aging performance.

The rate of thermal aging and the presence of oxygen are related to the type of conductor. The presence of oxygen can trigger the cracking reaction of polymer chains, accelerating the rate of thermal aging. Copper ions can enter the paint film through migration and become organic copper salts, which play a catalytic role in aging.

After taking out the sample, it should be cooled at room temperature to prevent it from being subjected to sudden cooling and affecting the test data.

2. thermal shock test

The thermal shock shock test is to study the shock of the paint film of the enamelled wire to thermal action under mechanical stress.

The paint film of enameled wire undergoes elongation deformation due to extension or winding, and the relative displacement between molecular chains stores internal stress within the paint film. When the paint film is heated, this stress is expressed in the form of film shrinkage. In the thermal shock test, the extended paint film itself shrinks due to heat, but the conductor bonded with the paint film prevents this shrinkage. The effect of internal and external stress is a test of the strength of the paint film. The film strength of different types of enameled wires varies, and the extent to which the strength of various paint films decreases with temperature rise also varies. At a certain temperature, the thermal shrinkage force of the paint film is greater than the strength of the paint film, causing the paint film to crack. Heat shock shock of the paint film is related to quality of the paint itself. For the same type of paint, it is also related to the ratio of raw materials

Too high or too low baking temperature will reduce the thermal shock performance.

The thermal shock performance of thick paint film is poor.

3. Heat shock, softening, and breakdown test

In the coil, the lower layer of the enameled wire is subjected to pressure caused by the tension of the upper layer of the enameled wire. If the enameled wire is subjected to pre baking or drying during impregnation, or operates at high temperatures, the paint film is softened by heat and gradually thinned under pressure, which may cause inter turn short circuits in the coil. The heat shock softening breakdown test measures the ability of a paint film to withstand thermal deformation under mechanical external forces, which is the ability to study the plastic deformation of a paint film under pressure at high temperatures. This test is a combination of heat, electricity, and force tests.

The heat softening breakdown performance of the paint film depends on the molecular structure of the paint film and the force between its molecular chains. Generally speaking, paint films containing more aliphatic linear molecular materials have poor breakdown performance, while paint films containing aromatic thermosetting resins have high breakdown performance. Excessive or tender baking of the paint film will also affect its breakdown performance.

Factors that affect experimental data include load weight, initial temperature, and heating rate.

Post time: May-09-2023