Coil Wire

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Soderon 155 » GP/MR-200 »


What is Coil Wire?

Coil wire, or magnet wire, is a copper or aluminium wire that has been coated with insulation for protection. Coil wire is designed to convert electric energy into magnetic energy.

What is Copper Wire used for?

Coil wire can be found in such applications as motors, transformers, hard disk drives, loudspeakers, electromagnets and inductors.

Coil Wire for Motor Coil Wire for Speaker Coil Wire for Transformer

Coil Wire Specifications

Conductor Type

Coil wire will almost always be made of either copper or aluminum, though silver wire is used in rare cases, such as loudspeaker voice coils.

Copper is the highest conducting non-precious metal, so aluminum's lower conductivity means it needs a much larger cross-section of aluminum to achieve equivalent ratings to a copper wire. Aluminum wire takes up more space than copper wire and is less efficient.

Copper is also 300% stronger than aluminum, which allows it to be used in extreme conditions.


Square, round and rectangular are all common shapes for coil wire. The wire shape is the determinant for how tightly the wire can be wound.

Rectangular wires lay flat and will, therefore, be used to create the tightest coils. Square wires will also create tight coils, since they will have minimal space between the turns. These wires are available for confined spaces and higher power applications.

Round wires will create coils that are the least tight because of large gaps between the turns, though this becomes less of an issue with extremely thin wire.

Rectangular Coil Wire Round Coil Wire

Pictured above: Rectangular wire (left), round wire (right)

Solid vs. Stranded Coil Wire

Solid wire is one strand of insulated wire, whereas stranded wire is multiple copper wires braided together.

Stranded wire is typically rigid, so applications where wires do not have to be moved often are ideal. Stranded wires a far more bendable than solid wires, with the wire flexibility of a stranded wire increasing with the number of strands. Stranded wire will have at least seven wires all together, with six wires wrapped around one in the middle.

Metal fatigue is when a wire is continuously subjected to loading and unloading, ultimately causing the wire material to crack. The flexibility of stranded wire helps to reduce the effect.

Because it has more surface area, stranded wire has more susceptibility to corrosion.

Solid Coil Wire Stranded Coil Wire

Pictured above: Solid copper wire (left), stranded wire (right)

Litz Wire

Litz wire contains multiple separately insulated wires braided together into one larger, insulated wire.

Litz wire is used in radio frequency inductors, and high-frequency transformers in order to minimize the skin-effect and proximity effect losses.

The proximity effect is when alternating current flows through one or more other nearby conductors, coils of wire for example, and the current becomes concentrated in the area of the conductor that is furthest away from the other conductors. This produces an increase in the resistance of the circuit.

The skin effect happens when alternating currents concentrate in a conductor's surface layer, increasing its effective resistance.

Litz Coil Wire


Wire insulations are generally going to made of either a fabric yarn or a thin enamel, which will increase the wire's thermal endurance.

What insulation really does is protect the wire from itself. The turns of bare wires, which do not have any insulation, cannot touch each other because, if they did, the wire would short out. Insulated wire allows the wound wire turns to touch, since the bare copper windings are no longer in danger of coming in contact. Wires can have hundreds or thousands of turns, so insulation for a wound wire is almost always necessary.

A high-temperature tape, made out of polyimide or fiberglass, is sometimes applied to square or rectangular wires that have thick insulation. An additional varnish can be placed on the windings as well. It is meant to provide extra insulation, help improve the wire's strength and increase its endurance.

Large power transformers that operate at high voltages will sometimes use insulations such as oil-impregnated paper or pressboard.

Polyurethane insulation overcoated with polyamide, a wire with a thermal rating of 155°C, and polyester-imide insulated wires overcoated with polyamide-imide, which have a thermal rating of 200°C, are both offered by TEMCo.

Insulated Coil Wire Insulated Coil Wire

Pictured above: Insulated wire (left), bare wire (right)

Wire Gauge

The American wire gauge (AWG) rating of the wire is used in both the U.S. and Canada to represent specific standards for round, solid wire, including diameter, weight, resistance and current.

In total, there are 44 standard wire gauges, the smallest being 0000 and the largest being 40. As the gauge goes up, the diameter and weight of the wire become smaller.

A 0000 wire will have a diameter of 11.684 mm and a weight of 640.5005 lbs per 1000 feet.

A 40 gauge wire will have a diameter of 0.0799 mm and a weight of 0.0299 lbs per 1000 feet.

Coil Wire Gauge

Temperature Rating/Thermal Class

Thermal class is measured in degrees celsius. It is the maximum temperature at which a wire will have a service life of 20,000 hours, a life that can can be extended if the wire is used at a temperature that is lower than the thermal class.

The thermal class is determined by the insulation that is used and can be either 130°, 155°, 180° or 200°, among others.

Bondable Coil Wire

Bondable wire eliminates the use of bobbins, the spindles around which the wire is wound by becoming a self-supporting coil. It achieves this through an extra adhesive film on top of the usual insulation that activates when heated up, bonding the wire turns together.

Bonding agents include epoxy, polyester and polyamide and can be applied three different ways:

  • Solvent bonding: Applied while the wire is winding or else the completed coiled wire must be dipped in the solvent.
  • Oven bonding: the wire will be heated up in an oven after it is the completion of the winding process. Larger coiled wires taking longer to bond, and the process can take anywhere from 10 to 30 minutes.
  • Resistance bonding: used for 34 gauge wires and up. The wound wire will be heated up with an electric current. The size of the wire, and the coil design, determine the amount of voltage, as well as the time necessary, for the process to finish.

Soldering Process

Soldering is the process of fusing two metals together. It is done by melting another metal, with a lower melting point, that will join the other two metals together after it becomes solid again.

For wire to be soldered, it may or may not need its enameled to be removed, depending on the wire. Some of the wire supplied by TEMCo will need insulation to be removed, while others will not.

Aluminum is not easily soldered, meaning connections can eventually corrode and fail.

Breakdown Voltage

Breakdown voltage can be one of 3 types: Grade 1, Grade 2 and Grade 3. Insulations with higher grades will have higher breakdown voltages, which is an indication of the dielectric strength of the insulation. Wires with smaller gauges come with higher breakdown voltages, since they will also have higher diameters.

The measurement of the enamel is called the insulation thickness, or build, which can come as single, heavy, triple or quadruple; single and heavy are the most popular builds.

To find the measurement of the enamel, take the diameter of the entire insulated wire and subtract just the diameter of the bare wire. The resulting number give you the insulation build.

Buy Coil Wire

View TEMCo's coil wire selection simply by clicking the links below. Wire is available in numerous gauges, temperature ratings, and insulations. Buy your coil wire from TEMCo today!

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

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