What's the wire enamel insulating varnish?
Wire enamel is a coating that creates a good insulating layer between wires in a winding. It is mainly used for the outer layer of bare copper wire, alloy wire and glass wire covered wire of various wire diameters to improve and stabilize the performance of enameled wire. It has high mechanical strength, is resistant to Freon refrigerant, has good compatibility with impregnating paint, and can meet the requirements of heat resistance, impact resistance and oil resistance. According to the heat-resistant temperature grade of insulating materials: Y (90°C), A (105°C), E (120°C), B (130°C), F (155°C), H (180°C), V (above 180°C) The main varieties of E and B enameled wires are acetal, polyurethane and polyester, and the main varieties of F and H enameled wires are polyesterimide, polyamideimide, polyester-amideimide and so on.
Polyvinyl Acetal/Formal Enamel For Enameled Wire - Advantages
“PV” product series have good resistance to chemicals and excellent mechanical, thermal and electrical properties and hence they are frequently used in formulations containing other ingredients such as phenolic resins. Polyvinyl Formal is highly versatile, having various outstanding properties, which makes it suitable for a wide range of applications. Specifically, Polyvinyl Formal is widely used for both, rectangular and round conductors. Polyvinyl Formal is also a key component in PVA based wire enamels that have outstanding resistance to transformer oil. These enamels provide excellent toughness, flexibility, and abrasion resistance. This material is available in five “PV” specifications with different molecular weights and different viscosities to suit various end usages. Polyvinyl Formal Enameled Wire is short of PVF Wire. The PVF enameled wire has a low temperature resistance level (105°C, 120°C), it is widely used in oil-immersed transformers due to its excellent high temperature hydrolysis resistance, especially the acetal enameled flat wire is used to make continuously transposed conductors, used in large transformers.
Application Of The Varnishes For Enamelling Of Winding Wires
The use of insulating varnishes for enamelling winding wires has some nuances, depending on the technology and equipment of the manufacturer, but the typical method of applying varnishes on copper wires includes:
1. Annealing. The heat treatment temperature, the purpose of which is to soften copper and increase its plasticity, depends on the properties, diameter, and cross section of the wires
2. Applying varnishes to the wires. At this stage, varnishes are applied to the wires, to create a coating
3. Enamel polymerization. The wires coated with the specified amount of varnish are sent to the furnace, where the solvent evaporates, and the enamel is cured. The temperature in the furnace can reach 700 C, but because the wires coated with the varnish spend a noticeably short time in the furnace, the enamel temperature usually does not exceed 300 C. It is worth noting that the furnace temperature, as well as the amount of time that the wires spend in the furnace may vary greatly depending on the technology and equipment of the wire manufacturer. This process is repeated until the desired enamel thickness is reached
4. Cooling of the wires. At this stage, the wires are cooled, often using fans. Sometimes, at this stage, grease is also applied to the wires
5. The wires are than assembled into coils
