Test 5:Electrical Resistance Of Enameled Wire

1. General notes on methods of test
Unless otherwise specified, all tests shall be carried out at a temperature from 15 C to 40 C and a relative humidity of 25 % to 75 %. Before measurements are made, the specimens shall be preconditioned under these atmospheric conditions for a time sufficient to allow the wire to reach stability.

The wire to be tested shall be removed from the packaging in such a way that the wire will not be subjected to tension or to unnecessary bends.Before each test,sufficient wire shall be discarded to ensure that any damaged wire is not included in the test specimens.

2. Test 1: Electrical resistance
Electrical resistance is the d.c. resistance at 20 °C of 1 m of wire.
The method used shall provide a precision of 0,5 %.

For bunched wires a length of up to 10 m shall be used and the ends shall be soldered before the measurement. When measuring the resistance to check for an excessive number of broken wires, a length of 10 m of bunched wire shall be used.

If the resistance Rt is measured at a temperature t other than 20 °C, the resistance R20 at 20 °C shall be calculated by means of the following formula:
R20 = Rt/[1+ (tt− 20)]
t: is the actual temperature in degrees Celsius during the measurement;
α: is the temperature coefficient in K-1.

In the temperature range from 15 °C to 25 °C, the temperature coefficient to be used shall be:
– for copper: α20 = 3,96 × 10-3 K-1;
– for aluminium: α20 = 4,07 × -3 K-1.

One test shall be made. The electrical resistance shall be reported.