Conductors—Round, Square, Rectangular, Copper, Aluminum
1. Surface Condition
Bare conductors shall be smooth, clean, and free of dirt, discoloration, corrosion, scales, or slivers, consistent with good commercial practice. Rectangular and square conductors shall be free from sharp, rough, or projecting edges. The corners on rectangular and square conductors shall be rounded so that the arcs of the radii merge smoothly into the flat surfaces. Wire with slight oxidation shall not be a cause
2. Resistivity
These resistivity values correspond to a conductivity, in percent International Annealed Copper Standard (IACS) of 100 for copper, 61.8 for aluminum, and 60.6 for aluminum EC 1350 alloys at 20°C (68°F). The resistivity shall be determined in accordance with ASTM B193 and shall not exceed the following values:
| Conductors | Maximum Resistivity | |
| Ohm-Circular mil/ft. | Ohm-mm2/m | |
| Copper | 10.371 | 0.017241 |
| Aluminum | 16.782 | 0.027898 |
| Aluminum EC 1350 Alloys* | 17.114 | 0.028450 |
This Standard specifies a minimum conductivity for copper of 100% IACS and shall not exclude the possibility of the use of coppers over 100% IACS. Likewise, a conductivity of 61.8% for aluminum and 60.6% for aluminum alloys shall not exclude the use of aluminum or aluminum alloys with higher conductivities in either case. The current state of conductor processing has made possible the use of higher conductivity metals.
NOTE—Since coils are a complex electromagnetic system there is no standardized method for calculating the current-carrying capacity of magnet wire. The maximum current density for an insulated magnet wire will be lower compared to a conductor employed in free air. In order to establish a practical maximum current density, users must take into account different variables including wire size, fill factor, space between wires, system design, and application.
3. Characteristics of Aluminum
The mechanical, electrical, and chemical characteristics of aluminum magnet wire differ from those of copper magnet wire because of the inherent differences in the conductor materials. These differences are reflected in certain test procedures and/or performance requirements for aluminum magnet wire, such as elongation, adherence and flexibility, heat shock, scrape resistance, continuity, and thermal endurance.
Film-coated aluminum round wire sizes 10-14 AWG (2.59-1.63 mm) shall have a yield strength not less than 7,000 psi (48.3 MPa) and a tensile strength not less than 13,000 psi (89.6 MPa); sizes 15-25 AWG (1.450-0.455 mm) shall have a yield strength not less than 8,000 psi (55.2 MPa) and a tensile strength not less than 13,000 psi (89.6 MPa). Large round sizes, all rectangular film-coated and all fibrous-covered wire shall have yield strengths not less than 9,000 psi (62.1 MPa).
NOTE—The testing procedure may include a pre-stretch of the specimen of 0.25%, which may remove small kinks, waves, and bends in the specimen prior to the test.
4. Characteristics of Copper
Excellent Electrical Conductivity
Good Plasticity
Strong Corrosion Resistance
Thermal Resistance
Mechanical Strength
Chemical Resistance
Thermal Stability and Solvent Resistance
High-Frequency Performance
Solderability
Abrasion and Scratch Resistance