Enamelled Wire Technology

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Enamelled wire technology Source: Enamelling technology I. Overview Enamelled wire is a major type of winding wire; it consists of a conductor and an insulating layer. The bare wire is first softened through annealing, and then coated with paint multiple times followed by baking. However, it is not easy to produce products that meet both standard requirements and customer demands. This is influenced by factors such as the quality of raw materials, process parameters, production equipment, and the environment. As a result, the quality characteristics of various enameled wires vary, but they all possess four key properties: mechanical properties, chemical properties, electrical properties, and thermal properties. Concepts and Classification 1. What is an electromagnetic wire? An electromagnetic wire is a type of wire with an insulating layer; it is used to convert electromagnetic energy in the form of windings, and is also known as a winding wire. 2. Classification: 2.1 By conductor material, it can be divided into: copper, aluminum, alloys, and composite materials. 2.2 By insulating material, it can be divided into: enameled wire, wrapped wire, and inorganic insulated wire. 2.3 By conductor shape, it can be divided into: round wire, flat wire, and special-shaped wire. 3. Classification of enameled wire: 3.1 By insulating material: 3.1.1 Acetal enameled wire; 3.1.2 Polyester enameled wire; 3.1.3 Polyurethane enameled wire; 3.1.4 Modified polyester enameled wire; 3.1.5 Polyester-imide enameled wire; 3.1.6 Polyamide-imide enameled wire; 3.1.7 Polyimide enameled wire; 3.1.8 Polyamide enameled wire; 3.1.9 Fusible enameled wire; 3.1.10 Flame-retardant enameled wire; 3.1.11 High-tensile enameled wire; 3.1.12 Self-lubricating enameled wire; 3.1.13 Ceramic-insulated electromagnetic wire; 3.1.14 Glass-film electromagnetic wire. 3.2 By application, enameled wire can be divided into: 3.2.1 Enameled wire for general use (ordinary wire), which is mainly used in ordinary motors, electrical appliances, and instruments. Winding wires for applications such as transformers include; polyester enameled wire, modified polyester enameled wire. 3.2.2 Heat-resistant enameled wire ； It is mainly used as winding wire for motors, electrical appliances, instruments, transformers, and other devices that operate in environments with temperatures of 180°C or higher. Such as polyester imide enameled wire, polyimide enameled wire, and polyester imide/polyamide imide composite enameled wire. 3.2.3 Enamelled wire for special purposes ； It refers to enameled wire that meets certain quality requirements and is used as winding wire in specific applications. Examples include:
– **Direct solderability**: Wire that can be soldered directly without the need to remove the enamel coating; such as direct-solderable polyurethane enameled wire and direct-solderable polyester-imide enameled wire.
– **Self-adhesion**: Enameled wire that can be wound directly into shape; this includes heat bonding (bonding at temperatures above 170°C, using direct electrical heating, such as in the deflection coils of color TVs and monitors) and low-temperature bonding (bonding at temperatures below 170°C, using hot air, such as in contactless cards and inductors). Solvent bonding is also used; alcohol-based solvents are common in this context, and it’s applied to components like microphones, speakers, and pickups.
– **Resistance to refrigerants**: Used in refrigeration motor windings; the enamel coating must have low-temperature resistance and be able to withstand corrosion from refrigerants. The lubricants on the surface of the enameled wire should not contain substances that precipitate at low temperatures.
– **High-frequency performance**: The enamel coating has minimal absorption of high frequencies, resulting in low attenuation; this leads to a higher Q value for the wound coils.
– **Corona resistance**: Reduces corona discharge caused by high-frequency pulses.
– **Melting characteristic**: The enameled wire melts when the temperature exceeds a certain limit; this is useful in small and ultra-small electrical devices, chargers, and power converters, as it prevents fires caused by increased coil temperature.
– **Flame-retardant property**: Flame retardants are added to the enamel coating to make it flame-retardant or difficult to ignite.
– **Pinhole-free after stretching**: The finished wire does not develop pinholes after being stretched; it exhibits good resistance to saltwater-induced pinholes, along with a high insulation breakdown voltage. It can be soldered directly and has high thermal stability. Enamel-wound stranded wires (Litz wires), mainly used for the field deflection coils of color TVs, the low-voltage windings of integrated flyback transformers (FBTs), switch-mode power supply transformers, yoke transformers, filter windings, as well as the windings of other audio-visual equipment and electronic instruments: Litz insulated stranded wires, simply known as Litz wires, are primarily used in high-frequency coils. They come in ordinary and self-adhesive types; generally, polyurethane-coated wires are used for single wires due to their high tensile strength. These wires use copper alloys as conductors, offering high tensile strength while retaining the properties of copper. Their tensile strength is greater than that of copper wires, and their electrical conductivity is over 83% that of copper. The insulation and coating properties are similar to those of copper-enamel wires, and they are used in read/write coils, voice coils, and head coils. Enamel-coated resistance wires include nickel-chromium coated wires, constantan coated wires, and manganin coated wires; these are the main materials used for producing various precision wire-wound resistors, featuring a low temperature coefficient and good linearity. TEX-E three-layer insulated wires have heat resistance ratings ranging from A to E* (105–120°C); they have excellent voltage resistance, reinforced insulation (test voltage = 3000 Vrms, 1 minute), can be soldered directly without removing the coating, and can be wound at high speeds using automatic winding machines. Their size range is 0.2–1.0 mm. Copper foil wires (tensu wires) have square or rectangular conductors and are mainly used in ultra-thin motors such as those in computer optical drives and hard drive motors. 3.3 Classified by conductor material: copper, aluminum, alloys, multi-metal composites, etc. 3.4 Classified by shape of the material: round wires, flat wires, hollow wires. 3.5 Classified by insulation thickness: Round wires: thin coating – 1, thick coating – 2, extra-thick coating – 3; Special wires (self-adhesive): thin coating – 1B, thick coating – 2B. Flat wires: ordinary coating – 1, extra-thick coating – 2. II. Models, codes, and product designation methods 1. Symbols and codes 1.1 Series codes: Enamel-wound wires: Q; Paper-wound wires: Z. 1.2 Conductor material: Copper conductor: T (omitted); Aluminum conductor: L; Copper-clad aluminum: CCA. 1.3 Insulation material: Oil-based paint: Y (omitted); Polyester paint: Z; Modified polyester paint: Z(G); Acetal paint: Q; Polyurethane paint: A; Polyamide paint: X; Polyimide paint: Y; Epoxy paint: H; Polyester-imide paint: ZY; Polyamide-imide: XY. 1.4 Characteristics of the conductor: Round wires: Y (omitted); Flat wires: B; Hollow wires: K. 1.5 Coating thickness: Round wires: thin coating – 1, thick coating – 2, extra-thick coating – 3; Flat wires: ordinary coating – 1, extra-thick coating – 2. 1.6 Heat resistance grade is indicated by /XXX. 2. Models 2.1 The models of enamel-wound wires are named using a combination of Chinese pinyin letters and Arabic numerals; these models consist of several components. Combining the above sections in order yields the enamel wire product model. 3. Enamelled wire products are indicated by model number, specifications, and standard code. 3.1 Examples of product representation methods ； A ； Polyester-coated copper round wire, thick paint film: heat rating of 130, nominal diameter of 1.000 mm, in accordance with GB6109．7－90 standard, indicated as ； QZ-2/130 1.000 GB6109.7-90B ； Polyester imide enameled copper flat wire ； Ordinary paint film, heat resistance grade 180; side a is 2.00 mm, side b is 6.300 mm. In accordance with GB/T7095.4-1995, it is expressed as ； QZYB-1/180 2.00X6.30 GB/T7995.4-1995 3.2 Oxygen-free round copper rod ； 3.2.1 Series code: Electric round copper rod: T3.2.2 According to appearance and content ； Oxygen-free round copper rod ； W Bright Round Copper Rod ； G3.2.3 Classified by state characteristics: soft state ； R hard state ； Y3.3.4 By performance characteristics: Level 1: –1; Level 2: –2. 3.2.5 Product model number ； Specification and standard number indication ； For example: a solid oxygen-free round copper rod with a diameter of 6.7 mm and grade 1 hardness is denoted as TWY-16.7 GB39523.3; the bare copper wire corresponds to this as well ； 3.3.1 Bare copper wire: T3.3.2 Classified by state characteristics: Soft state ； R hard state ； Y3.3.3 By material shape: flat wire ； B circular line ； Y (omitted) 3.3.4 Example ； Rigid round copper bare wire with a diameter of 3.00 mm, TY2.00 GB2953-89