Electromagnetic wire production process and quality judgment method

1. Preparation

Raw materials for magnet wires are transported to the production site by carts. The preparation of insulating varnish is completed in the paint preparation room. According to the different insulation degrees of various electromagnetic wires, a certain proportion of paint and thinner is fully mixed and evenly added to the enamelling machine.

Two, drawing

The wire drawing is carried out in the wire drawing machine, and it is drawn once or multiple times according to the required wire diameter. The temperature during drawing can generally reach 60-100°C, and water-soluble lubricants are used for lubrication and cooling. When the temperature exceeds 100°C, supplementary cooling and heat removal are performed.

Three, washing

Water washing is water purified by hydrochloric acid and caustic soda, and the electromagnetic wire is washed with high-pressure water to remove oil stains on its surface.

4. Annealing

Annealing is generally carried out in an annealing furnace by means of electric heating, and the annealing temperature is generally controlled at 300-600°C, and water vapor is used for protection during annealing to prevent oxidation. After annealing, use a blower for air cooling, and enter the impregnation section at about 40°C.

5. Dipping

The impregnation section is carried out in the enamelling machine, and it is completed several times according to the requirements of the insulation layer. When dipping, add appropriate proportion of diluent according to the needs of the coating. The thinner contains flammable and toxic liquids such as cresol and xylene.

6. Drying

The drying of the electromagnetic wire is carried out in a drying furnace, and the drying temperature depends on the speed of the wire drawing, generally 300-400°C. It can reach up to 670°C. Drying and exhaust gas are carried out simultaneously. The exhaust gas (temperature is 300-400°C) contains toxic and flammable vapors such as cresol, phenol, xylene, etc. After the catalytic reaction reaches the environmental protection index, it is discharged into the atmosphere by the exhaust fan.

7. Take-up

The wire take-up is to use the wire take-up device to wind the finished electromagnetic wire on the wire reel after drying. A small amount of lubricant (974 gasoline, cyclohexane) needs to be added when taking up the line.

8. Packaging and warehousing

After passing the inspection, put the wrapped plastic film into cartons or paper tubes, pack them into wire trailers according to the needs of users, and load and unload them into special warehouses.

After understanding the production process of the magnet wire, let me introduce the quality judgment and inspection methods of the magnet wire.

Electromagnetic wire size detection control

Bare Wire Diameter Tolerance:

The allowable tolerance of the bare wire refers to the allowable deviation between the actual value of the bare wire diameter and the specified value. From the point of view of use, it is hoped that the smaller the tolerance, the better, which is conducive to the calculation of resistance, turns, etc. during design. However, the die hole of the mold will be worn and deformed during the stretching process during manufacturing. If the tolerance requirements are too strict, the mold must be replaced frequently, resulting in difficulties in process operation and mold supply. When formulating standards, the use requirements and the control ability of the production unit should be weighed to be economical and applicable.

Section out of roundness:

The difference between the maximum measured value and the minimum measured value of the diameter of the same section of the guideline. Excessive out-of-roundness will cause the color of the enameled wire to fade, the color sense will be poor, and it will not be conducive to the process arrangement of the wire. This item is not easy to detect and tends to be controlled by the magnet wire manufacturer.

Maximum outer diameter:

If the maximum outer diameter is out of tolerance, the size of the coil will increase, which will affect the slot fill rate.

Minimum film thickness:

If the paint film is too thin, it is easy to produce pinholes, which will lead to the decline of voltage resistance, scratch resistance, chemical resistance and aging resistance, which will lead to serious quality hidden dangers in the motor.

Enameled wire mechanical performance detection and control

In the process of motor coil winding and embedding, there are mechanical forces acting on the enameled wire, such as stretching force, friction force and bending force during winding; there is friction in the embedding process; there are factors during the operation of the motor Turn-to-turn friction caused by vibration. If the core wire or paint film of the enameled wire does not meet the requirements, the above-mentioned mechanical forces will cause damage to the enameled wire to varying degrees. Therefore, it is very necessary to establish elongation test, rebound angle test, scratch resistance, and various mechanical performance tests on the basis of simulating the use requirements.

Enameled wire heat resistance test

The heat resistance of enameled wire is an important indicator, especially for motors and components or windings with demanding temperature rise requirements. It directly affects the design and use of electrical equipment. The temperature rise of electrical equipment is limited by the enameled wire and other insulating materials used. If enameled wire with high heat resistance and supporting materials can be used, better reliability can be obtained under the condition of unchanged structure, or the external size, weight and Energy-saving effects of non-ferrous metals and other material consumption.

Heat aging test:

It takes half a year to one year to measure the thermal performance of enameled wire by the method of thermal life assessment (UL test). The aging test lacks the simulation in application, but it still has practical significance in controlling the quality of the paint and the degree of baking of the paint film in the production process of the magnet wire.

Thermal Shock Test:

The thermal shock resistance test is to study the ability of the paint film of the enameled wire to withstand heat under the action of mechanical stress.

Heat softening breakdown test:

In the coil, the enameled wire of the lower layer is under the pressure caused by the tension of the enameled wire of the upper layer. If the enameled wire is in the pre-baking or drying process of immersion, or when it is operated at high temperature, the paint film is softened by heat and gradually squeezed under pressure. A turn-to-turn short circuit of the coil occurs.

Enameled wire electrical performance detection and control

A thin layer of paint film on the enameled wire must ensure that the passing current circulates along the core wire in the coil to ensure that the electromagnetic induction enables the motor to function. If the dielectric properties of the varnish film are insufficient, it will cause a short circuit in the coil.

DC Resistance:

If the resistance value of the enameled wire is too large or too small, the total resistance of the wound warp coil will change. The change range of the total resistance exceeds the allowable tolerance in the design, which will affect the balance of the three-phase voltage of the motor and the temperature rise of the motor.

Breakdown voltage:

Under the action of a strong electric field, the bound electrons in the polymer can gain energy from the electric field and become free electrons, moving in the direction of the electric field. When the free electrons collide with other bound electrons during the movement, they are excited to become free electrons, so that more and more free electrons increase the conductivity of the polymer. When the electric field strength exceeds a certain value, a hole connecting the two electrodes is formed in the polymer, so that the increasing current passes through it, and the polymer loses its insulating properties and is broken down. The strength of the applied voltage at this time is called the breakdown voltage. The heat brought by the voltage breakdown will cause thermal damage to the polymer, which will melt and burn.

Factors affecting the breakdown voltage: paint film thickness and out-of-roundness, degree of curing, and foreign impurities in the paint. Factors affecting the breakdown voltage test data: twisting number, voltage application time, voltage boosting speed, paint film elongation, and temperature during pressure application.

Film Continuity:

The enameled wire has a large number of coils, tight winding, and many wire-to-wire contact surfaces. If there are many pinholes in the enameled wire paint film, the pinholes between the two turns may overlap, causing a short circuit.

Enameled wire chemical resistance test

The chemical resistance of enameled wire includes acid resistance, alkali resistance, salt spray resistance, moisture resistance, oil resistance, solvent resistance, refrigerant resistance, radiation resistance and other aspects. This performance is controlled by the magnet wire manufacturer.

During the coil impregnation process, the enameled wire not only has to withstand the thermal performance test of thermal shock and softening breakdown, but also can withstand the erosion of toluene, xylene, petroleum solvent, oil and other solvents in the impregnating varnish. Different paint films have different tolerances to different solvents. When impregnating, an impregnating paint containing only solvents suitable for enameled wires should be selected according to the characteristics of enameled wires.

Winding is a key process in the production and processing of motor windings. In addition to the fully automatic winding and embedding equipment, most of the production process is to process the winding and embedding separately. In the winding process, on the one hand, it is necessary to ensure the coil shape, turn The number and other parameters meet the requirements. On the other hand, it is necessary to ensure that the electromagnetic wire is not damaged during the coil winding process.

During the production and processing of the electromagnetic wire, the coiling method and arrangement of the wire have a great influence on the later use. If the arrangement is scattered or part of the electromagnetic wire penetrates into the bobbin, it will lead to uneven transmission of the electromagnetic wire during the coil winding process, affecting The forming effect of the coil will cause damage to the electromagnetic wire in severe cases.

In order to prevent the occurrence of similar problems, motor manufacturers should combine their respective winding processes to reach a consensus with the electromagnetic wire supplier, and control the weight of the single shaft, the coordination between the bobbin and equipment, and the arrangement of the electromagnetic wire to ensure the output of production. meet the requirements of use.