Electromagnetic wire is one of the main raw materials for electric motors . The conductor used for windings or coils is called electromagnetic wire. There are many types of electromagnetic wire, which can be divided into three types according to their cross-sectional shape: round wire, flat wire, and strip wire. Round wire and flat wire have standardized cross-sectional dimensions. The cross-sectional dimensions of strip wire can be ordered from the wire manufacturer according to design requirements. Based on the characteristics and uses of the insulation layer, electromagnetic wire can be divided into four main categories: enameled wire, wrapped wire, inorganic insulated wire, and special electromagnetic wire. Today, Ms. Can will summarize and share the basic performance of electromagnetic wire according to its insulation characteristics.
1 enameled wire
Enameled wire requires a uniform, smooth, and completely covered enamel film (few pinholes). The conductor diameter and enamel film thickness should conform to national standards. The performance of enameled wire is determined by the enamel film, generally including the following items:
(1) Mechanical properties. The coating film should be scratch resistant, elastic, and have appropriate softness and elongation to ensure that it can withstand friction, bending, stretching and compression without damage during winding, embedding and stretching, shaping and other processes.
(2) Electrical performance. The main requirement is a high breakdown voltage of the enamel film. For enameled wires used in high-frequency and high-voltage motor windings, a small loss tangent of the enamel film is required. For enameled wires with a diameter of less than 0.5 mm, the number of pinholes is a very important indicator for evaluating their electrical performance. Many motor manufacturers equip their incoming electromagnetic wires with enamel film continuity testers to check the number of pinholes.
(3) Thermal properties. These include the softening breakdown, thermal aging, and thermal shock properties of the paint film. The softening breakdown property indicates the paint film's ability to resist heat deformation under certain pressure; the thermal aging property reflects the paint film's ability to retain a certain degree of elasticity after being subjected to heat for a short period of time; the thermal shock property reflects the paint film's ability to withstand thermal shock (rapid cooling and rapid heating) without breaking during baking, impregnation, or overload operation.
(4) Chemical properties. This indicates the ability of the paint film to withstand corrosion from chemicals such as acids, alkalis, salt spray, organic solvents, or refrigerants.
2. Wrapping wire
Currently, the commonly used winding 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 around bare conductors or enameled wires, and then impregnating and baking it with adhesive insulating varnish. The electrical and mechanical properties of glass fiber wrapped wire are better than those of enameled wire, and its heat resistance level depends on the heat resistance of the adhesive insulating varnish and the enameled wire.
In addition to the requirement that dimensional tolerances must not exceed the specified limits, when flat wire is bent 180° on its wide side, its insulation should not have any defects such as peeling, cracking, exposed copper or varnish, or broken fibers; and it should have a certain insulation resistance and breakdown voltage.
Film-wrapped wires possess superior mechanical and electrical properties, making them a valuable type of wrapping wire. Currently used types include glass fiber-wrapped polyester film wrapping wires and polyimide film wrapping wires. Polyimide film wrapping wires offer resistance to high and low temperatures and radiation; they also exhibit good sealing performance, electrothermal aging resistance, and abrasion resistance; and their slot space utilization is higher than that of glass fiber-wrapped wires. Glass fiber-wrapped polyester film wrapping wires possess excellent electrical and mechanical properties, but their insulation layer is thicker.
3 Inorganic Insulated Wire
The inorganic insulated wires used for motor windings are mainly aluminum wire with anodized film. This is achieved by anodizing the aluminum wire to form a dense aluminum oxide film on its surface. It has advantages such as a thin insulation layer, good heat resistance, and radiation resistance; however, the oxide film is porous, resulting in a low breakdown voltage; it also has relatively poor bending resistance, scratch resistance, and acid and alkali resistance.
4 Special Electromagnetic Wires
Specialty electromagnetic wires possess insulation structures and properties suitable for specific environments. Examples include PVC-insulated electromagnetic wires and polyethylene-insulated nylon-sheathed electromagnetic wires used in submersible motor windings. The former has better water resistance but lower slot space utilization; the insulation layer is easily damaged during coil winding, and it is used in general submersible motors. The latter has good water resistance and high sheath mechanical strength, but lower slot space utilization, and is commonly used in water-filled submersible motors.
Disclaimer: This article is a reprint. If it involves copyright issues, please contact us promptly for deletion (QQ: 2737591964). We apologize for any inconvenience.
