Shall I load more than the current rating of the given wire cable?

[digiajay]

I have UNINYVIN cable with 111A as Rated Current. There is no details on its Rated Voltage.

Suppose if this cable is 230V rated, is it safe to load more than 111A at 12V?

My idea on this is, the power rating of the cable remains in the limit as given below
111A at 230V = 25.5KW
111A at 12V = 1.33 KW

Throw me some light on this side of electrical.

-Ajay

 

[jagadishputta1]

NO because the resistance is constant so it is not safe that cable...

your power calculations is ok but do the power calculation with respective Resistance

suppose Resistance is x Ohm

at 111A at 230V the Power loss in that cable = 111*111*x

so if the current increase more than 111A may the cable may damage because of resistance constant..

 

[chuckey]

The current limit on cable is due to the cables resistance and the temperature rating of the insulation and how the heat is conducted away from the outside of the cable. So the 111 Amps should be also equated with the temperature rise of the cable, so if you run the cable in a hot place, its current rating will be lower and at the melting point of the insulation its zero. Conversely if the cable is buried in a marsh where the heat can be conducted away, it can carry more current.
If you have say 10 m. of this wire running at 100A, it might drop .8V so at mains voltage, you would get 230V - .8 = 229.2 ~ 99.7% of the input volts. If the supply was 12V, it would still drop .8V, you would get 11.2V or 94% of the input voltage, so at 12V you need BIGGER cable, not for the current rating but for the voltage drop.
Frank

 

[jagadishputta1]

Yes whatever chuckey point also correct...obviously it is depends on temperature the drop in wire is also matter

 

[BradtheRad]

Links to charts of wire gauges showing safe amp-carrying capacity:

http://amasci.com/tesla/wire1.html



Here's a link to another wire gauge table. Its ampacity values are much different than the other tables.

**broken link removed**

Possible reason for the disparity: One source may base ampacity on a higher temperature which makes the wire get too hot to hold, while the other source may use a lower temperature where copper's electrical characteristics start to change even though it is only warm.

 

[jeffrey samuel]

the line losses will be very high in lower voltages and so the drop through the wire will be very high