Inrush current carrying capacity of Cable

[PQ]

Is a 50mm2 XLPE Power Cable rated 230A can withstand a starting current of a motor with a magnitude of 640A for about 3-5 cycles? Is is possible for us to have a 10-15 motor start-up/day... The power cables is rated for 90C continuous operation and can carry a 250C short-circuit rating. Is there a chart were we can find to relate the 90C and 250C temp. unit to current unit

 

[ERaySir]

PQ

The manufacturer should have a destruction or failure curve for the cable similar to a fuse curve on a current-time log-log graph. Should be considered when doing coordination study. Some coordination study software provides generic information. If you have the plant coordination study is could have that information on there.

Best Regards



Ray Micallef, P. Eng.
Power Generation/Utility Industry

 

[RajT]

With the mag of 630A lasting 5 cycles and with 15 starts per day, you should have no worries at all.

 

[GreyGoose]

A very good reference if you can get your hands on one is the Okonite publication: Engineering Data for Copper and Aluminum Conductor Electrical Cables. There are lots of informative charts & tables in this book on power cables, including a chart which shows the short circuit withstand capabilities of different size cables over time. as per previous post, you should have no problem with your particular selection.

 

[cuky2000]

The inrush current is typically less than the SC. However, the principles to determine the withstand capability of the cable could be similar for SC and for Inrush.

In the vast majority of cases, Inrush effect on cable withstand capability should not be a concern. If you would like to proof that check the enclose information that could be used as a tool for this purpose.

http://www.kerite.com/catalog/catalogfiles/short_circuit_limitations.htm

 

[jbartos]

Suggestion: The 15 starts per day is a very ambiguous input. It actually depends how close in time succession are those starts. Is there any jogging or plugging involved?
Normally, the cable tends to withstand higher currents than the motor when it comes to more frequent starts.

 

[PQ]

Guys,
Thanks a lot, especially to cuky2000 atleast i can support my claims that it will not be a problem with the cable..As per jbartos normally the problem will be the motor for it has a limitation with no. of start-up...

regards