When placed under heavy electrical load conditions beyond the designed current carrying capacity, wire/cable will heat and cause damage to the conductor, wire/cable insulation, and potentially other components. At what electrical load the wire begins to degrade and produce smoke varies depending on the conductor material, conductor plating, and insulation. Those wires/cable able to handle higher electrical current beyond their normal operational limits (such as in the case of electrical shorting conditions) are preferable.
The purpose of the time/current to smoke test is to determine the time (and electrical current) necessary for a wire specimen to produce smoke. The pass/fail criteria for this test is based on the particular wire/cable specification but is typically based on the specimen able to sustain an electrical current level (e.g. 15 Amps) without producing visible smoke.
Parameters that can be adjusted in this test include:
- Specimen preconditioning
- Rate of current increase
- Specimen length
- Enclosure type