Magnet wire is used to create coils that, when energized, produce an electromagnetic field. Typically, these insulated electrical conductors are made of copper or aluminum. Magnet wire is available in large and small sizes, and may have a square, round, or rectangular cross-section. Products may be wound on cores or used without a core to produce a magnetic field. Normally, however, magnet wire is insulated with an enamel coating. Applications include motors, relays, solenoids, headphones, speakers, computer hard drives, voice coils, potentiometers, transformers, and current sensors. Selecting magnet wire requires an analysis of specifications and features. Insulation type is an important parameter to consider. Choices include products that use a polyvinyl formal resin, polyimide resin, or polyamide resin; polyurethane base insulation enamel; or film insulation with a modified polyester basecoat and nylon topcoat. Magnet wire may also be insulated with a polyester resin or internal lubricating film. Most products are single-coated, but double-coated magnet wire is also commonly available. Other product specifications for magnet wire include thermal class and size range. Examples include Class 1 magnet wire (heavy build) and Class 2 magnet wire (single build). Magnet wire may be coated with a smooth surface so that products can be more easily wound with automated machinery. In addition to windability, magnet wire features include resistance to hydrolysis (an important consideration for use in hermetic systems), abrasion and chemical resistance, and resistance to common solvents. Magnet wire may also provide heat-shock resistance and burnout resistance, as well as excellent dielectric properties. In terms of applications, magnet wire is used mainly in motors, transformers, and other electromagnetic equipment. Some products are used to help transform electrical into mechanical energy. Examples include industrial machinery, cars and trucks, and HVAC systems. Magnet wire is also used with generators, which transform mechanical energy into electrical energy. Electrical-to-electrical energy transformation involves transformers. Magnet wire may comply with standards and certifications from the National Electrical Manufacturers Association (NEMA), the American National Standards Institute (ANSI), and the International Electrotechnical Commission (IEC). NEMA’s Magnet Wire section maintains and publishes the ANSI/NEMA MW 1000-2003 standard. Other relevant NEMA standards and publications include MW 785-2001, MW 765-2003, and MW 750-2001. Liaisons with outside organizations include the American Society for Testing Materials (ASTM) and Underwriters Laboratories (UL).
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