Shielded 600V Feeder Cable

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Breaker19

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Does anyone have any information on why it would be advantageous to install shielded feeder cable to the incoming AC section on a VFD lineup vs non-shielded? Or if braided straps would stop harmonics from polluting up the line. I can understand using it for the load side of the VFD but do not understand, fully, for the line side prior the filter, which already contains an isolation transformer.
I just can't fathom the reasoning behind it, especially since 3c/750 w/g shld is around 80 dollars a foot. Then again I am not an engineer.
Thanks in advance.
 

Electric-Light

Senior Member
Does anyone have any information on why it would be advantageous to install shielded feeder cable to the incoming AC section on a VFD lineup vs non-shielded? Or if braided straps would stop harmonics from polluting up the line. I can understand using it for the load side of the VFD but do not understand, fully, for the line side prior the filter, which already contains an isolation transformer.
I just can't fathom the reasoning behind it, especially since 3c/750 w/g shld is around 80 dollars a foot. Then again I am not an engineer.
Thanks in advance.
Running the cables in grounded EMC already provides excellent shielding.
 

Jraef

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Electrical Engineer
The idea behind shielding is to prevent the cables from becoming radio transmitting antennae. If you are laying them in tray, shielding is a must. If pulling them in grounded conduit, as Electric-Light said the conduit serves the same function. Pulling shielded cable inside of grounded conduit is a waste IMHO.
 

jdsmith

Senior Member
Location
Ohio
Jraef is correct. Two engineers from Belden and one from Rockwell wrote a paper about this that was presented at the 1999 IEEE PCIC conference. It's one of the best papers out there on VFD cabling - this feeder cable antenna effect is just one of a number of topics covered. They also discuss the life expectancy of various cable insulations under years of reflected wave voltage pulses - this is the only place I've seen any serious analysis on VFD cable life.
 
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