Size the conductor up
For the same resistance, raise the conductor area by about 1.6 times (about 1.27 times the diameter) and check the window or slot can take it.
Winding wire guide
Aluminium Magnet Wire: Types, Thermal Classes & Selection
Aluminium magnet wire is an insulated aluminium conductor, usually EC-grade 1350, used to wind coils in transformers, motors, reactors and inductors. For the same resistance it needs about 1.6 times the cross-section of copper but weighs roughly half as much and costs less. This guide explains the insulation types, thermal classes, round and flat shapes, standards and the design points that make aluminium windings reliable.
- Conductor
- EC aluminium 1350
- Shapes
- Round 0.4 – 4.0 mm · flat
- Thermal class
- 130 – 220 °C
- Standards
- IEC 60317 · NEMA MW 1000
What is aluminium magnet wire?
Magnet wire is any insulated conductor used to build electromagnetic coils. The insulation must be thin, so the coil stays compact, yet strong enough electrically, thermally and mechanically to survive winding, varnishing and years of operation. Aluminium magnet wire uses an aluminium conductor in place of copper.
There are three main families. Enamelled wire has one or more thin polymer coatings baked onto the conductor and is the most common type. Paper-covered wire is wrapped with layers of insulating paper and is used mainly in oil-filled transformers. Glass-fibre-covered wire is served with glass yarn and varnish for high-temperature dry-type transformers and traction equipment. All three are magnet wire; "winding wire" is the wider term that also includes bare conductors.
Aluminium magnet wire is typically drawn from EC (electrical conductor) grade 1350 aluminium, with a conductivity of about 61 – 62 % IACS in the annealed condition. It is annealed soft before or during enamelling so it winds easily.
Aluminium versus copper magnet wire
| Property | Aluminium 1350 (annealed) | Copper (annealed) |
|---|---|---|
| Conductivity | About 61 – 62 % IACS | 100 % IACS (reference) |
| Resistivity at 20 °C | About 0.028 Ω·mm²/m | 0.01724 Ω·mm²/m |
| Density | 2.70 g/cm³ | 8.89 g/cm³ |
| Cross-section for equal resistance | About 1.6 × | 1 × |
| Weight for equal resistance | About 0.5 × | 1 × |
| Tensile strength (soft) | Low; easier to stretch or nick | About three times higher |
| Thermal expansion | 23 µm/m·°C | 17 µm/m·°C |
| Termination | Crimp, weld or special connectors; native oxide resists soldering | Easy soldering, crimping, brazing |
The larger conductor means a bigger coil and, in a transformer, a slightly larger core window, so an aluminium design is not a one-for-one swap. In return, the winding is lighter and cheaper, and the larger section spreads short-circuit forces over more area. Many distribution and dry-type transformers are wound in aluminium for exactly these reasons.
Values are typical published figures for EC aluminium and annealed copper. Actual conductor resistance is guaranteed per size by the wire standard and reported on the test certificate.
Enamel types and thermal classes
The thermal class is the temperature, in °C, at which the insulation is rated for a long service life under the IEC 60172 endurance test. Choose a class at least as high as the winding hot-spot temperature, with margin for overloads.
| Enamel | Typical thermal class | Characteristics | Typical uses |
|---|---|---|---|
| Polyvinyl acetal | 105 – 120 | Tough, good abrasion resistance and compatibility with transformer oil | Oil-filled distribution transformers |
| Polyurethane | 130 – 155 | Solderable on copper; on aluminium, termination still needs mechanical or welded joints | Small coils, relays |
| Polyester | 130 – 155 | Economical general-purpose enamel | Fans, small motors, ballasts, small transformers |
| Polyesterimide | 180 | Good heat-shock and solvent resistance | Compressors, power tools, industrial motors |
| Polyesterimide with polyamide-imide overcoat | 200 | Hard, abrasion-resistant dual coat for tough winding | Motors, dry-type transformers, inverter-fed machines |
| Polyamide-imide / polyimide | 220 and above | Highest thermal and chemical resistance | High-temperature and special-duty coils |
Paper-covered aluminium conductors are rated as part of the transformer insulation system (oil and paper), and glass-fibre-covered conductors take their rating from the glass and impregnating varnish, commonly class 155 – 200. Insulation build (grade 1, 2 or 3 in IEC terms; single, heavy, triple in NEMA terms) sets the breakdown voltage.
For individual products, see class 130/155 polyester, class 180 polyesterimide, class 200 polyamide-imide overcoat and class 120 acetal wires.
Round or flat (rectangular) wire?
Round wire
Round enamelled aluminium wire
- Typical diameter
- 0.4 – 4.0 mm
- Strengths
- Flexible, easy to wind on automatic machines, economical
- Uses
- Small and medium motors, small transformers, ballasts, relays, induction coils
Flat wire
Rectangular enamelled or covered aluminium wire
- Typical size
- Width about 2 – 25 mm, thickness about 0.8 – 6 mm
- Strengths
- Packs with far less empty space, so more conductor fits in the same window or slot; better heat removal
- Uses
- Dry-type and distribution transformers, reactors, large inductors, some motors
Round wires leave unavoidable gaps between turns. Rectangular wire stacks face to face, giving a considerably higher fill factor, lower resistance for the same window and shorter heat paths. The trade-off is harder winding (the wire must not twist), larger minimum bend radii on edgewise bends and higher price per kilogram. Our enamelled aluminium flat wire page lists flat sizes. For very large transformer windings, aluminium foil and strip is an alternative to wire.
Standards for aluminium magnet wire
| Standard | Scope |
|---|---|
| IEC 60317-0-3 | General requirements for enamelled round aluminium wire |
| IEC 60317-0-9 | General requirements for enamelled rectangular aluminium wire |
| IEC 60317 (product parts) | Individual enamel types and thermal classes |
| IEC 60851 series | Test methods for winding wires |
| IEC 60172 | Determination of the temperature index of enamelled wire |
| IEC 60085 | Thermal classification of electrical insulation |
| NEMA MW 1000 | North American magnet wire standard covering copper and aluminium, round and rectangular |
| ASTM B609 | Annealed and intermediate-temper 1350 aluminium round wire for electrical purposes |
| ASTM B233 | 1350 aluminium drawing stock (rod) for electrical purposes |
Tell us which standard and product part your drawing references, and the wire will be supplied and tested to it. Routine tests include conductor dimensions and resistance, enamel thickness and continuity, breakdown voltage, elongation, adhesion and flexibility, heat shock and solvent resistance.
Designing and winding with aluminium wire
Control winding tension
Soft aluminium stretches more readily than copper. Lower tension and smooth guides prevent necking, which raises resistance and thins the enamel.
Plan the terminations
The oxide film prevents ordinary soldering. Use compression crimps rated for aluminium, ultrasonic or TIG welding, or cold-pressure welding to copper leads.
Avoid galvanic attack
Joints between aluminium and copper must be sealed against moisture or made with bimetal connectors to prevent galvanic corrosion.
Allow for creep and expansion
Aluminium expands more and creeps under constant clamp load. Use spring washers or connectors designed for aluminium at bolted joints.
Check varnish compatibility
Confirm the impregnating varnish or resin is compatible with the enamel and the thermal class of the system.
Typical applications and configurations
| Application | Typical wire | Thermal class |
|---|---|---|
| Oil-filled distribution transformers | Paper-covered or acetal-enamelled flat and round aluminium | 105 – 120 (oil system) |
| Dry-type transformers and reactors | Flat aluminium with polyesterimide/PAI enamel or glass-fibre covering; foil windings | 155 – 200 |
| Fan, pump and appliance motors | Round polyester or polyesterimide enamelled aluminium | 130 – 180 |
| Air-conditioner compressor motors | Round enamelled aluminium with refrigerant-resistant enamel | 180 – 200 |
| Ballasts, chokes and small transformers | Round polyester-enamelled aluminium | 130 – 155 |
| Induction cooker coils | Fine aluminium or copper-clad aluminium wire | 180 – 200 |
Copper-clad aluminium (CCA) magnet wire, an aluminium core with a thin metallurgically bonded copper layer, is used where some of the weight saving of aluminium is wanted with easier, copper-like terminations; see CCA wire. Traction motors for electric vehicles are still mainly wound with copper; aluminium is used in some auxiliary motors and continues to be evaluated for traction designs.
How to order aluminium magnet wire
- ConductorShape and size: diameter, or width × thickness with corner radius for flat wire.
- InsulationEnamel type or covering, thermal class and build (grade 1/2/3, or single/heavy).
- StandardIEC 60317 part, NEMA MW 1000 type, or your own specification and test requirements.
- PackagingSpool type and net weight per spool, or coils for flat wire.
- Documents and shippingTest certificate per lot with resistance, dimensions and electrical tests; shipped on EXW, FOB, CIF or DAP terms.
References and standards
- IEC 60317-0-3 – Specifications for particular types of winding wires: enamelled round aluminium wire, general requirements
- IEC 60317-0-9 – Enamelled rectangular aluminium wire, general requirements
- ANSI/NEMA MW 1000 – Magnet Wire
- ASTM B609 – Aluminum 1350 Round Wire, Annealed and Intermediate Tempers, for Electrical Purposes
- IEC 60085 – Electrical insulation: thermal evaluation and designation
- The Aluminum Association – Aluminum Electrical Conductor Handbook
Aluminium (aluminum) magnet wire: frequently asked questions
Is aluminium magnet wire as good as copper?
It conducts about 61 % as well as copper, so the conductor must be about 1.6 times larger in area for the same resistance. With that allowance, an aluminium winding performs the same electrically, weighs about half as much and costs less; it needs more space and careful terminations.
What is the difference between magnet wire and enamelled wire?
Enamelled wire is one kind of magnet wire. Magnet wire also includes paper-covered and glass-fibre-covered conductors used for coils.
Which thermal class should I choose?
Choose a class above the winding hot-spot temperature with a margin for overload: class 130 – 155 for fans and small transformers, 180 – 200 for compressors, industrial motors and dry-type transformers.
How do you terminate aluminium magnet wire?
Use crimp connectors rated for aluminium, ultrasonic or TIG welding, or cold-pressure welding to copper leads. Ordinary soft soldering is unreliable because of the oxide film, and aluminium-to-copper joints must be protected from moisture.
What sizes are available?
Round wire is typically 0.4 – 4.0 mm diameter; flat wire is typically about 2 – 25 mm wide and 0.8 – 6 mm thick. Other sizes can be supplied to specification.
Which aluminium alloy is used for magnet wire?
EC-grade 1350 aluminium, drawn from 1350 rod and annealed for flexibility, with conductivity of about 61 – 62 % IACS.
Sourcing aluminium magnet wire?
Send the conductor size, insulation, thermal class, standard and quantity. We will reply with availability, test documentation and a delivered price.
