Flexible Motor Supply cable

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eljefetaco

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Location
Fanwood, NJ
Don't know where this question belongs on the forum so I am putting it here. We are doing a job in North NJ the German Company who did the designed for a dust collection system specfied this cable. It is being run to a 460v 3phase roof top motor, I am not sure of the FLC but I looked and cross-referenced the NEC and it is okay. My question is what is with all the shielding. I have 4 number 4 RHW-s , three groups of plastic insulation four al braids approx 12 g stranded, and a foil rapper. The name on the product is
" Alpha wire -Er4067-L Series V- P/N V16004 VFD Cable 4C4 Shielded 1000v Flexible Motor Supply cable 600v Type TC-ER (UL) RHW-2 CDRS XLPE/PVC 90c Dry/Wet Sun Res Dir Bur--- LL7874 CSA AWM I/II A/B 1000v 90c FT4"

I think it is Variable Frequency Drive, 4 conductor Tray cable/ Direct burial but what is with all the shields? Can some one explain all the drains. It is being run in a 2" Gal. by itself and terminates at motor disconnect and in the control panel.
 
weressl

weressl

Esteemed Member
Location
Texas by the Gulf, geat crab, great shrimp
eljefetaco said:
Don't know where this question belongs on the forum so I am putting it here. We are doing a job in North NJ the German Company who did the designed for a dust collection system specfied this cable. It is being run to a 460v 3phase roof top motor, I am not sure of the FLC but I looked and cross-referenced the NEC and it is okay. My question is what is with all the shielding. I have 4 number 4 RHW-s , three groups of plastic insulation four al braids approx 12 g stranded, and a foil rapper. The name on the product is
" Alpha wire -Er4067-L Series V- P/N V16004 VFD Cable 4C4 Shielded 1000v Flexible Motor Supply cable 600v Type TC-ER (UL) RHW-2 CDRS XLPE/PVC 90c Dry/Wet Sun Res Dir Bur--- LL7874 CSA AWM I/II A/B 1000v 90c FT4"

I think it is Variable Frequency Drive, 4 conductor Tray cable/ Direct burial but what is with all the shields? Can some one explain all the drains. It is being run in a 2" Gal. by itself and terminates at motor disconnect and in the control panel.
Click to expand...

I am little confused about the description. Al braids? perhaps nickel plated copper.http://www.alphawire.com/Products/C...ndustrial-Cable/IndustrialSeriesV/V16004.aspx

The 3 black conductors are the phase wires, the 4th is a green or green with yellow stripe is the ground. The shielding should be connected to ground and is to minimize RF and EMI emissions and to help equalize unbalanced voltage stresses occurring at the harmonic levels. There is an ongoing debate if the shielding needs to be grounded at both end or only at the drive's end and weather it should be connected to the PE or P terminals.
 
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Doug S.

Senior Member
Location
West Michigan
weressl said:
There is an ongoing debate if the shielding needs to be grounded at both end or only at the drive's end and weather it should be connected to the PE or P terminals.
Click to expand...

I have found the debate to be both entertaining and stressful. My guess is that the Germans are going to push hard for grounding the shield at both ends. However this is ONLY effective when there is a LOW impedance path between both points. We use multi-point grounding in our facility, and it works great, but where it's done each machine or component has a MINIMUM of a #6 for grounding.

As far as Europeans, (I know this is a broad stroke) they love their cable.
If you talk with the project engineer and explain, politely, that cable is a far less common practice here, and that the wire will be enclosed in a conduit through it's entire length, he may be ok w/ good 'ole thhn.


My 2?
Doug S.
 
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nakulak

Senior Member
I am often suprised by the fact that in the year 2000+, with all the technological advancements of the past 200 yrs, especially in the last 100 with electricity and electronics, that there is so much equipment with shielding issues and so few effective standards. We install some high end flame detection/gas detection/deluge systems now and then (these systems are used on aircraft hangars/oil rigs/lng plants etc), and called for the lon loop shielding to be bonded at the devices and at the controllers. well, because the units use pulse modulation, the shield feedback interfered with the proper operation of some of the controllers, and we ended up bonding the shileds together but taking them off the bus (similar to low end fire alarm installation methods). Now you would think that fm/ul approved systems would have some kind of standard for rf/emil shielding attenuation (as opposed to just direct bonding) for these type of systems, as well as for what I assume is a similar kind of interferenc form the above mentioned vfd drives ? what is wrong with our manufacturers that all of these grounding/bonding/shielding issues arise and so many field installations are made to simply "make it work", instead of well engineered methods to a proper standard ? (or am I just ignorant ?)
 
Besoeker

Besoeker

Senior Member
Location
UK
nakulak said:
I am often suprised by the fact that in the year 2000+, with all the technological advancements of the past 200 yrs, especially in the last 100 with electricity and electronics, that there is so much equipment with shielding issues and so few effective standards.
Click to expand...
Probably not helpful for you abut there are a number of EU directives dealing with this.
http://www.compliance-club.com/
 
weressl

weressl

Esteemed Member
Location
Texas by the Gulf, geat crab, great shrimp
Doug S. said:
I have found the debate to be both entertaining and stressful. My guess is that the Germans are going to push hard for grounding the shield at both ends. However this is ONLY effective when there is a LOW impedance path between both points. We use multi-point grounding in our facility, and it works great, but where it's done each machine or component has a MINIMUM of a #6 for grounding.

As far as Europeans, (I know this is a broad stroke) they love their cable.
If you talk with the project engineer and explain, politely, that cable is a far less common practice here, and that the wire will be enclosed in a conduit through it's entire length, he may be ok w/ good 'ole thhn.


My 2?
Doug S.
Click to expand...

The conduit, which is at varying distances from the conductors, is less effective shielding than braiding. MC cable is better. I don't know where will you find THHN with insulating rating that will withstand the overvoltages. We do use ASD grade composite cables except on retrofits where nothing else changes but the controller. I prefer the cables with the 3 grounding cables equally spaced between the phase conductors. It provides an equalized voltage stress distribution from phase to ground.

There is a slew of MEF, EMI, RF standards in the ANSI system, but ther are not mandatory and hardly anybody pays attention to those.
 
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TxEngr

Senior Member
Location
North Florida
You are correct in your assumption that this cable is for variable frequency drive use. The cable is constructed in such a way as to control the capacitance of the cable to help prevent standing wave reflections caused by the high switching frequencies of PWM based VFDs. This is typically only a problem on longer length (over 50 feet) cables going to drives. The high frequency switching of the VFDs can cause standing waves on the cable that can be twice the peak voltage of the system. This can cause motor failures at the internal connection points or catastrophic failure of capacitors in the drive. If you look at your motor specs, you'll most likely see that it is rated for 1600 or more volts, which is designed to withstand the same problem. The uninsulated grounds (drains) are symmetrically arranged around the conductors in the cable as part of the design to control capacitances.

I normally purchase this cable as type MC rather than run it in conduit and the grounds are tied at both ends. Since you're not carrying a signal, you don't have to worry about ground loops.

I hope this help to explain things a bit. There's more info on this on the I-net if you want to pursue it further.

TxEngr
 
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