Hi John:
> More significantly, its resistance affects the maximum short-circuit
> current that can flow.
This is a valid consideration with regard to safety.
Given a 6-amp maximum, 0.75 sq mm size, and 2 meters
length.
In North America, 2X rated current is the 1-minute
operating time of a fuse or circuit-breaker. The
maximum resistance of the power cord (assuming a
short at the load end of the cord) would be:
120 V
R = ------- = 4 ohms.
30 A
>From the wire tables, 0.75 sq mm wire is about 0.023
ohm/meter.
For 4 ohms resistance we would need 4/0.023 or 173
meters of wire, or a 2-wire cord of about 85 meters.
In continental Europe, using the same assumptions
about current and operating time, the maximum
resistance of the cord would be:
230 V
R = ------- = 7.1 ohms.
32 A
The wire length would be 7.1/0.023 or 312 meters,
and the cord length would be 156 meters.
So, the 2-meter length restriction (0.092 ohms)
appears not to be in consideration of the short-
circuit current. It appears that a 0.75 sq mm
cord could be 20 meters in length (0.92 ohms) and
still operate the overcurrent device.
Best regards,
Rich
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