Wire Size
FIRE HAZARD To satisfy safety requirements, load wires must be large enough not
to overheat when carrying the maximum short circuit current of the power supply. If
there is more than one load, then any pair of load wires must be capable of safely
carrying the full-rated current of the supply. Paralleled load wires may be required
for larger-ampacity power supplies.
The following table lists the characteristics of AWG (American Wire Gauge) copper wire.
AWG Equivalent mm
2
Nearest Metric
size
Ampacity
(Note1)
Resistance
(Note2)
18 0.823 1.0 mm
2
14 6.385
16 1.31 1.5 mm
2
18 4.016
14 2.08 2.5 mm
2
25 2.526
12 3.31 4 mm
2
30 1.589
10 5.26 6 mm
2
40 0.9994
8 8.37 10 mm
2
60 0.6285
6 13.30 16 mm
2
80 0.3953
4 21.15 25 mm
2
105 0.2486
2 33.62 35 mm
2
140 0.1564
1/0 53.48 70 mm
2
195 0.0983
2/0 67.43 70 mm
2
225 0.0779
3/0 84.95 95 mm
2
260 0.0618
Note 1. Ampacity is based on 26-30 °C ambient temperature with the conductor rated at 60 °C.
Ampacity decreases at higher temperatures.
Note 2. Resistance is in ohms/1000 feet, at 20 °C wire temperature.
Along with conductor temperature, you must also consider voltage drop when selecting wire sizes.
The power supply will tolerate a voltage drop of 1 V per lead while maintaining the specified output
programming and measurement accuracy (see N6900 and N7900 specifications). Voltage drops of up
to 25% of the rated output voltage per lead will be tolerated with only slightly reduced output
programming and measurement accuracy. Of course, any voltage drop in the load leads reduces the
maximum voltage available at the load. The load lead drop must be subtracted from the rated voltage
of the power supply to determine the maximum voltage available at the load.
2 Installing the Instrument
70 Keysight N6900/N7900 Series Operating and Service Guide
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