Magnet Wire

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Soderon 155 » GP/MR-200 »


What is Magnet Wire?

Copper or aluminium wire, covered with a layer of insulation or enamel, will be known as magnet wire, which is used to convert electric energy into magnetic energy.


Applications that contain tight coils of wire will use magnet wire. Transformers, inductors, motors, speakers, hard disk head actuators, or electromagnets all use coiled magnet wire.

Magnet Wire for Motor Magnet Wire for Speaker Magnet Wire for Transformer

Magnet Wire Specifications

Conductor Type

Copper is the default metal for most magnet wire, but aluminum is used in some applications as well, including large transformers and loudspeaker coils.

Due to it having lower conductivity than copper, aluminum wire will need to have a cross section that is 1.6 times larger to replicate the same current capabilities as a copper wire. This makes copper wire generally more efficient and less bulky than aluminum, as it will take more aluminum to achieve the same ratings.

At the same time, aluminum does have the advantage of being more resistant to corrosion than copper.


The most common shapes for magnet wire are square, round and rectangular. The wire shapes is important in determining how tightly the wire can be coiled.

Square copper wires contain less space between the turns when they are formed in a coil and are often used in confined spaces. Applications that require higher power, and that have a larger capacity and wire gauge, will also need square wire coils.

Round wire has more spaces between the wires and cannot be wound as tightly as square wire.

Rectangular wire is the most easily wound since it lays flat. Rectangular wires are laminated into a flat ribbon of flexible insulating plastic. Flattened wire is used on edge-wound coil springs.


The color of the wire will have no effect on the insulation, diameter, current, or any other element of how the wire will function.

The reason that wires will come in different colors is to differentiate circuits for soldering. By making the wires different colors, it makes it clear which conductor is coming from which circuit.

Wires can come in a variety of colors, including red, green and amber. Manufacturers will sometimes provide customers with a wire in a specific color if it is required.

Color Magnet Wire


Magnet wire insulation enhances the wire's thermal endurance and serves to protect it. Wires that contain no insulation are known as bare wire. The turns of bare wire cannot touch each other, since this would cause the wire to short itself out. Insulated wire can be wound so that the wires are touching. In the case of a wire needing to have hundreds or thousands of turns, the wire will require the protection that the insulation provides.

Magnet wire insulations are either a thin varnish, a yarn made out of polyester or fiberglass, or both.

Square and rectangular wires with thicker insulation builds might come with an extra high-temperature tape made of polyimide or fiberglass. The coils might also be covered with a varnish that is meant to increase both the strength and the reliability of the wire.

Older insulation materials used to be constructed of materials like cotton, paper, or silk. These are only useful for low-temperature applications, however, as they generally have a thermal rating of 105°C.

Different insulation types will have different specifications, including thermal capacity, diameter, gauge and application.

Polyester and polyurethane are two of the many different kinds of insulation that a magnet wire might use. Wires can also be double coated, meaning they will have both an undercoat and a topcoat.

TEMCo offers two dual insulation wires: Soderon 155, which has a polyurethane insulation with a polyamide overcoat, and GP/MR-200, which comes with a polyester-imide insulation overcoated with polyamide-imide.

Double coated wire is used to strengthen the wire and increase its durability. It also allows the wire to take on the properties of both insulations. For example, the insulation of the GP/MR 200 gives the wire increased dielectric properties and greater chemical resistance to common solvents and refrigerants. The dual insulation of the Soderon 155 allows it to be more resistant to solvents and increases its windability.

Wire Gauge

Wire diameter can be determined by the American wire gauge (AWG) number of the wire. AWG is used in the U.S. and Canada and represents the specific characteristics of a solid, round wire, such as diameter, resistance and current.

Diameter and AWG number have an inverse relationship: as one goes up, the other goes down. For example, a wire with a diameter of 4.621 millimeters will have a gauge of 5, while a wire with a diameter that measures 0.143 millimeters will have an gauge of 35.

American wire gauge sizes go from from 0000-40. The smallest gauge wire will have a diameter of 11.684 mm, while the largest gauge wire has a diameter of 0.0799 mm.

Any diameter beyond those gauge sizes will be so thin that they will be theoretical.

Magnet Wire Gauge


Wire weight will also be based on AWG standards and will have work the same way as the diameter: as the gauge becomes greater, the weight of the wire will decrease. This makes sense when you realize that the diameter is decreasing, and less wire means less weight.

The reason that wire is measured in weight, instead of length, is it ensures accuracy. It is much easier to simply weight a wire than to lay out miles of wire for measurement.

The largest wire weight is 640.5005 lbs per 1000 feet, for a gauge of 0000. The 40 gauge wire has a weight of 0.0299 lbs per 1000 feet.

Temperature Rating/Thermal Class

The temperature, in degree celsius, at which a wire will have a 20,000 hour service life is called the thermal class, or temperature rating. If the wire is used at a lower temperature, this will extend the wire's service life.

130°, 155°, 180° and 200° are some common temperatures found in different types of insulation, with the maximum thermal class being 250°.

Bondable Magnet Wire

Bondable wire contains an extra adhesive film on top of the usual insulation that activate when heated up. It will bond the turn to turn windings of the wire into a self-supporting coil. eliminating the need for bobbins, the spindles around which the wire is wound.

Bonding agents include epoxy, polyester and polyamide.

There are three main types of bonding: solvent, oven and resistance.

A solvent bonding coat will be applied while the wire is winding, or else the coiled wire will be dipped in the solvent after the winding has completed.

For oven bonding and resistance bonding, the wire is fully wound. It will then will be put into an oven, or given an electric current for resistance bonding, that heats the coil up, thus allowing it to bond.

Oven bonding can take 10 to 30 minutes, with the time varying with the size of the coiled wire. The amount of voltage and time it will take for resistance bonding to finish is dependent on how big the wire is and the design of the coil. Wires that have a gauge of 34 or higher will use resistance bonding.

Soldering Process

Soldering is the process by which two wires are fused together, or to a circuit board. The process involves a third metal with a lower melting points, lead or tin for example, which will be melted down and will merge the wires together.

Some wire does not need to have its enamel removed before it is soldered, but this depends on the type of wire. Some, like the GP/MR-200 wire offered by TEMCo, will require that the insulation be removed from the wire first before the wire can be soldered, while the Soderon 155 wire does not, as the insulation will act as a flux when it is burned.

Breakdown Voltage

Breakdown voltage is an indication of the dielectric strength of the wire's enamel insulation. The breakdown voltage can be of 3 types: Grade 1, Grade 2 and Grade 3. The thicker the insulation, the higher the grade. Higher ambient temperatures can lead to a reduction in breakdown voltage.

The insulation thickness, or build, is the measurement of the enamel or insulation that has been added to the bare wire. The total diameter of the wire, minus the diameter of the insulation, will give you the insulation build.

Insulation build can be single, heavy, triple or quadruple, with single and heavy being the commonly uses.

Breakdown voltage is based on AWG standards. Smaller gauges resulting in higher breakdown voltages, given that smaller gauges have larger diameters.

Where can I buy Magnet Wire?

TEMCo offers wires in different gauges, temperature ratings and insulations. View our product selection below to purchase your magnet wire. If you don't see what you need, you can call TEMCo for a quote on any type of wire today!

View Soderon 155 Wire Selection View GP/MR-200 Wire Selection

Call us at 877.474.8209