What is the difference between magnet enameled wire and wrapped wire? What are the welding methods?

Electromagnetic wire is a conductive metal wire with an insulating layer, mainly used to wind various motors and transformer coils. Electromagnetic wire is divided into round and flat types according to the shape of the conductor, and enameled wire and wrapped wire according to the insulating material.

Electromagnetic wire is actually a coil or winding used for motors, electrical appliances and electrical instruments. It is an electric wire that has realized electromagnetic energy conversion, also known as winding wire. According to the material, structure, heat resistance level and purpose of the insulation layer, it can be divided into four categories: enameled wire, wrapped wire, inorganic insulated electromagnetic wire, and special electromagnetic wire.

◆  Enameled wire: The insulating varnish is applied to the conductive wire core and dried to form a paint film as an insulating layer. Ordinary enameled wire can be divided into acetal, polyester, polyurethane, epoxy, polyesterimide, oily enameled wire, etc. Special enameled wires include self-adhesive straight welding enameled wire, self-adhesive enameled wire, refrigerant-resistant enameled wire, etc.

◆  Wrapped electromagnetic wire: electromagnetic wire that is tightly wrapped with insulating paper, glass fiber, natural silk and synthetic silk on bare wire or enameled wire to form an insulating layer is called wrapped electromagnetic wire. It includes silk-covered wire, glass-covered wire, paper-covered wire, film-wrapped wire, etc.

◆  Inorganic insulated electromagnetic wire: electromagnetic wire with inorganic insulating materials such as ceramic, glass film, oxide film, etc. as insulating layer.

◆  Special electromagnetic wire: electromagnetic wire with insulation structure and characteristics suitable for special occasions, such as medium and high frequency winding wire, polyethylene insulated nylon sheathed submersible motor winding, etc.

Basic properties of electromagnetic wire enameled wire and wrapped wire

• Enameled wire

Enameled wire requires uniform, smooth and complete coating (few pinholes). The wire diameter and paint film thickness should comply with national standards. The performance of enameled wire is determined by the paint film, generally including the following items:

 1. Mechanical properties. The paint film should be scratch-resistant, elastic, and have appropriate softness and elongation to ensure that the paint film can withstand friction, bending, stretching and compression without damage during winding, embedding, stretching and shaping.

 2. Electrical properties. The main requirement is that the breakdown voltage of the paint film should be high. For enameled wire used in high-frequency and high-voltage motor windings, the loss tangent of the paint film should be small. For enameled wire with a diameter of less than 0.5, the number of pinholes is a very important indicator for evaluating its electrical properties; many motor manufacturers are equipped with paint film continuity testers during the inspection of electromagnetic wire entering the factory to check the number of pinholes.

 3. Thermal properties. Including the softening breakdown, thermal aging and thermal shock properties of the paint film. The softening breakdown property indicates the ability of the paint film to resist heat deformation under a certain pressure; the thermal aging property reflects the ability of the paint film to retain a certain elasticity after being subjected to a short period of heat; the thermal shock property reflects the ability of the paint film to withstand thermal shock (sudden cooling, rapid heating) without breaking during baking, dipping or overload operation.

 4. Chemical properties. Indicates the ability of the paint film to withstand corrosion by chemicals such as acid, alkali, salt spray, organic solvents or refrigerants.

• Wrapped wire

Currently, the commonly used wrapped wires for motor windings are mainly glass fiber wrapped wire and film wrapped wire.

Glass fiber wrapped wire is made by tightly winding alkali-free glass fiber on bare wire or enameled wire, and then impregnated and melted with adhesive insulating varnish. The electrical and mechanical properties of glass fiber wrapped wire are better than those of enameled wire, and the heat resistance grade depends on the heat resistance of adhesive insulating varnish and enameled wire. The requirements for glass fiber wrapped wire are that, in addition to the dimensional tolerance not exceeding the specified value, when the flat wire is bent 180° according to the wide surface, its insulation should not fall off, crack, expose copper or paint, or break fibers; and it should have a certain insulation resistance and breakdown voltage.

Film wrapped wire has higher mechanical and electrical properties and is a very valuable wrapped wire. Currently used are glass fiber wrapped polyester film wrapped wire and polyimide film wrapped wire. Polyimide film wrapped wire is resistant to high temperature, low temperature and radiation; and has good sealing, electrothermal aging and drag resistance; the slot space utilization rate is higher than that of glass fiber wrapped wire. Glass fiber wrapped polyester film wrapped wire has good electrical and mechanical properties, but the insulation layer is thicker.

• Inorganic insulated wire

The inorganic insulated wire used for motor windings mainly includes oxide film aluminum wire. It uses anodizing to form a dense aluminum oxide film on the surface of the aluminum wire. It has the advantages of thin insulation layer, good heat resistance and radiation resistance; but the oxide film is porous, so the breakdown voltage is low; at the same time, the bending resistance, scratch resistance and acid and alkali resistance are also poor.

• Special electromagnetic wire

Special electromagnetic wire has insulation structure and performance suitable for special environments. For example, polyvinyl chloride insulated electromagnetic wire and polyethylene insulated nylon sheathed electromagnetic wire used for submersible motor windings. The former has better water resistance, but low slot space utilization rate; the insulation layer is easily damaged when winding the coil, and is used for general submersible motors. The latter has good water resistance and high mechanical strength of the sheath, but the slot space utilization rate is low, and it is often used in water-filled submersible motors.

Using a hydrogen-oxygen flame welding machine to weld enameled wire not only meets the workpiece processing requirements, but also does not need to remove the paint skin, and replaces gas cylinders such as oxyacetylene, which is safe, efficient, energy-saving and environmentally friendly.

What are the welding methods?

• The working principle of hydrogen-oxygen flame enameled wire welding:

Water is composed of hydrogen and oxygen elements. In a specific electrolytic cell, water can be decomposed into hydrogen ions and hydroxide ions, in which hydrogen ions move to the cathode to generate hydrogen, and hydroxide ions move to the anode to generate oxygen. Hydrogen is a fuel, and oxygen can be used to support combustion. A hydrogen-oxygen flame can be formed by igniting a specific hydrogen-oxygen flame gun, and the enameled wire can be quickly welded.

• Characteristics of hydrogen-oxygen flame enameled wire welding：

 1. Convenient: During the working process, the hydrogen-oxygen flame enameled wire welding machine only uses water and electricity to generate the flame for welding operations, and does not require additional gas cylinders, so it is easy to operate. Compared with traditional enameled wire welding, there is no need to remove the paint, and because the flame temperature is as high as 2800℃, the excess lead can be directly burned off to keep the fusion part flat.

 2. Safety: The hydrogen-oxygen flame enameled wire welding machine is ready for use, does not store gas, and avoids the risk of gas cylinder explosion.

 3. Efficiency: The flame temperature of the hydrogen-oxygen flame enameled wire welding machine can reach 2800 degrees, which is higher than the temperature of other gases and the flame is fine, which is convenient for precise and efficient operation.

 4. Energy saving: The hydrogen-oxygen flame enameled wire welding machine only uses a small amount of water and electricity, and the cost of use is saved by more than 40% compared with gas cylinders.

 5. Environmental protection: The raw materials are pollution-free, the product is water, and no black smoke exhaust gas is generated during the combustion process.

Original Source:Magnet Wires for Power Industry