What kind of wire do you use in electromagnets?
You should
use magnet wire. Duh. This is copper or
aluminum wire with a thin insulation to prevent short circuits. It is
single-strand wire insulated with enamel, varnish, cotton, glass, asbestos or
some combination of these. To meet the immense variety of uses and to gain
competitive advantage, a great number of kinds of enamel and of fiber
insulations have been developed and are widely available.
"The Institute of Electrical and Electronics Engineers (IEEE) thermal classes of insulation, defined by upper temperature limits at which the untreated insulation will have a life expectancy of at least 20,000 hours, are
In general, materials such as cotton, paper, and silk are class O. Organic materials, such as oleoresinous and Formvar enamels, varnish-treated cotton, paper, and silk are class A. Asbestos, mica, silicone varnishes, and polyamide are class H, while various synthetic enamels fall in the B and F classes. The polyesterimide enamels, however, are capable of withstanding temperatures of 356-392F (180-200C).
Almost all magnet wire is insulated soft-drawn electrolytic copper, but aluminum is being used more, especially in times when copper is scarce or high-priced and where space is not limiting. Round aluminum wire, being soft, flattens under pressure giving a higher space factor in coils than might otherwise be expected. At temperatures above 392F (200C) copper oxidizes rapidly; it also becomes brittle when under stress at such temperatures. Its high-temperature strength is increased considerably by adding a small amount of silver (about 30 oz/ton or 1kg/metric ton). Anodized aluminum is preferred for higher temperatures, up to 572F (300C) or more, while copper nickel wire with an anodized aluminum coating may be operated at still higher temperatures."
Source: "McGraw-Hill Encyclopedia of Science & Technology", Vol. 10 LEP-MES, 8th Edition, (c) 1997, ISBN 9-07-911504-7 (set)
Visit one of the major wire manufacturers, WireTron, at www.wiretron.com for free software that provides lots of information about (what else?) wires. It can help you select and understand size, material, strength, resistance, maximum current, weight, insulation and other factors.
Last update May 7, 2007 by Barry Hansen ©1998-2007