Enamelled Wire (Magnet Wire): Types, Classes and Sizes

What enamelled wire is and how it is made

The enamel on magnet wire is a film only a few hundredths of a millimetre thick, yet it must withstand hundreds or thousands of volts between turns, survive the abrasion and stretching of high-speed winding, resist impregnating varnishes and oils, and keep its properties for decades at the winding hot-spot temperature.

1. DrawingElectrical-grade rod (for aluminium, usually 1350 EC grade) is drawn through a series of dies to the final conductor diameter or rolled to a rectangular section.
2. AnnealingThe drawn wire is annealed in-line to restore softness and maximum conductivity, which also makes it easy to wind and form.
3. EnamellingLiquid enamel is applied by dies or felts and cured in an oven; the cycle is repeated many times to build the film in thin, even layers, which avoids pinholes and solvent blisters.
4. LubricationA thin surface lubricant lowers friction so the wire runs smoothly through winding machines.
5. Spooling and testingWire is wound on spools under controlled tension and sampled for dimensional, electrical, thermal and mechanical tests.

Enamelled wire is classified by conductor material, shape (round, rectangular or square) and enamel system. This page focuses on the enamel systems and on round aluminium wire; rectangular wire is covered in our enamelled aluminium flat wire guide.

Aluminium, copper-clad aluminium and copper conductors

An aluminium winding needs about 1.6 times the conductor area of copper for the same resistance, so the wire diameter grows by about 27 %. In exchange the conductor weighs about half as much and the material cost is substantially lower. Aluminium wire is soft and ductile, so winding tension must be controlled to avoid stretching thin sizes. Terminations need methods suited to aluminium, such as welding, crimping with appropriate terminals or cold-pressure welding, because the oxide film prevents ordinary soldering without special fluxes.

Metline supplies enamelled aluminium and copper-clad aluminium winding wire. For coils that must be terminated to copper leads, use bimetallic terminals or welding methods made for aluminium.

Enamel types and thermal classes

The thermal class (temperature index) is the temperature in °C at which the insulation reaches a defined life in accelerated ageing to IEC 60172. A higher class allows a hotter winding or a longer life at the same temperature. Choose a class at or above the hot-spot temperature of your design.

Dual-coat systems combine a base coat chosen for adhesion and thermal endurance with a tougher overcoat for abrasion, chemical and refrigerant resistance. Nylon (polyamide) overcoats are used on polyurethane and polyester wires to reduce friction and protect against winding damage.

Insulation grades and round wire dimensions

IEC grades describe the insulation build. Grade 1 is the thinnest film and leaves the most room for conductor; Grade 2 roughly doubles the build for higher breakdown voltage and robustness; Grade 3 is thicker again for demanding voltage or mechanical duty. NEMA uses the terms single, heavy, triple and quadruple build in the same sense. The table gives values for round aluminium wire: the minimum increase in diameter produced by the enamel and the maximum overall diameter, for each grade, plus calculated conductor resistance.

Dimensional values from the IEC 60317-0-3 dimension table for enamelled round aluminium wire (they mirror the copper values of IEC 60317-0-1). Resistance is calculated with 0.02826 Ω·mm²/m; the standard sets the permitted resistance band.

How enamelled wire is tested

IEC 60851 defines the test methods referenced by every IEC 60317 product sheet. The most important checks are:

Choosing the right enamelled wire

• Start from the hot-spot temperature of the winding and add margin for overloads; that sets the minimum thermal class.
• Check the environment: transformer oil favours acetal or compatible polyester systems; hermetic compressors need refrigerant-qualified 200-class wire.
• Consider the drive: inverter-fed motors see voltage spikes; specify dual-coat or corona-resistant enamels and a heavier grade.
• Match the termination method: polyurethane allows solder stripping on copper and CCA; plain aluminium wire is usually welded or crimped.
• Pick the grade from voltage and winding stress: Grade 1 for low-voltage, carefully wound coils; Grade 2 or 3 for higher turn-to-turn voltage or aggressive winding.
• Confirm varnish compatibility with your impregnation resin, especially for 180-class and higher systems.

Applications of enamelled aluminium wire

How to order

1. SpecifyConductor (aluminium or CCA), nominal size, enamel type, thermal class and grade, and the standard (IEC 60317 sheet or NEMA MW 1000 type).
2. PackagingSpool type and net weight per spool to suit your winding equipment.
3. QuoteWe confirm availability, test documentation and terms (EXW, FOB, CIF or DAP).
4. DeliverSpools are packed in cartons or crates on pallets with a test report for each lot.

Related winding wire pages

Enamelled (enameled) wire: frequently asked questions