VFD motor cables 1

[thinker]

We use Europe built VFDs based on PWM inverter driven AC
induction motors. Vendors recommend to use a special VFD cable with braided shield and three symmetrical ground
conductors (brands OLFLEX, HELUKABEL). The problem is that these cables are built to European standards and are not
UL listed or approved. Can anybody advise whether similar
cables are manufactured in US? So far we were able to find
only corrugated aluminum armor cables with three symmetrical
ground wires, but we can not use them since a flexibility
is required. Size range from 1/0 to 500 kcim.

 

[dydt]

as far as i know OLFLEX is UL and CSA approved..we are
using them in some of our installations here in north america....for german and italian machines...

i will check again...

dydt

 

[busbar]

I can't imagine that tripling of ground conductors could have any operational advantage— particularly for voltage-stress limitation in unshielded-dielectric cables. Sounds like nothing more than a {swallowed wholesale by the drive/motor manufacturer} marketing gimmick. A 2kV conductor-insulation rating seems like it should be of a lot higher priority. Termination quality on a single equipment-ground conductor would seem more of an issue. They may want to avoid boilerplate change on their equipment specs and are just being obstinate.

Although—that conductor arrangement seems to be the norm for ANSI G/GC-type flexible supply cord.

 

[thinker]

Busbar,
There are some other important issues. One of a big problems
in VFD systems is excessive currents in protective earth
ground (PE)bus of PWM inverter causing control problems or
even damaging the drive control system.The usage of the motor cable with single ground wire would contribute to this problem, because this single ground wire spirals among phase conductors, and unbalanced magnetic fields from phase
conductors induce noise currents in ground wire. I remember
reading a technical paper with the information that high-
frequency common-mode noise currents as high as 15A have been measured in VFD system and caused noise and tuning problems in the VFD inverter.A cable with three ground conductors spaced symmetrically with the three phase conductors develop significantly lower levels of common-mode
noise currents in the inverter's PE bus.
General Electric for their new VFD ("Innovation" series) sets the usage of the cable with three symmetrical ground as
the most preferable option.To summarize: VFD cables with
symmetrical ground conductors have justifiable application.

 

[redtrumpet]

The only one I can think of is Nexans Drive RX, but I think this is one of the corrugated aluminum armor ones. Try phoning Douglas Reith of Nexans at 1-800-268-9473 to see if he can offer the construction in a non-armoured version.

 

[robertb]

Consider Belden VFD cables.

 

[jbartos]

Suggestion: Please notice that there is not just a noise, there are also reflected waves. Visit

http://bwcecom.belden.com/college/PDF/VFD_Flyer.pdf

http://bwcecom.belden.com/college/techpprs/capwmtp.htm

(very impressive and informative paper)

http://bwcecom.belden.com/college/Prodbull/NP147.pdf

http://www.manufacturing.net/ctl/index.asp?layout=articleWebzine&articleId=CA204960

http://www.lappusa.com/

http://www.a-aelectric.com/products/manufacturers/manufacturers.html

etc. for more info

 

[Laplacian]

http://www.ab.com/drives/techpapers/ieee/IECON95_bearing.pdf

This specification is most likely to minimize currents circulating through the rotor and bearings.

 

[jbartos]

Suggestion: The reflected waves are influencing length of cable and somewhat the type of cables. See

http://www.ab.com/drives/techpapers/ieee/IAS_98 final.PDF

http://www.ab.com/drives/techpapers/ieee/APEC_98.pdf

for more info

 

[jeby]

There are VFD Type P Marine Shipboard Cables rated .6/1kV manufactured by Draka USA/BIW Cable Systems to the construction requirements of IEEE Std. 45 (1998 edition) and the performance requirements of IEEE Std. 45 & IEC 92-3 with the insulated grounding conductors and special braided shielding required by select drive manufacturers. These cables utilize rope stranded conductor suitable for both fixed and repeated flexing applications. The marine shipboard VFD cables do not utilize the mechanically onerous corrugated aluminim sheath addressed previously that fractures after any repeated flexing or high vibration. Send inquiries for more information to jeby@ebyenergy.com.

 

[jbartos]

Suggestion: Visit

http://www.generalcable.com

for
Polyrad® XT 125 Marine
UL/IEC/IEEE
TYPE P
Marine Shipboard Cable
Onshore/Offshore Oil
Exploration Cable
IEEE-45 Type P Cable for Oil Exploration Applications
Superior Flexibility
Offers Resistance to Synthetic Drilling Fluids
Smaller & Lighter 110°C Temperature Rated Cable
Superior Physical, Chemical & Environmental Properties
-65°C to +110°C
Per IEEE-45/IEEE-1580
Marine Shipboard Cable
Onshore/Offshore Oil Exploration
Cable
IEEE-45/IEEE-1580
IEEE-383
IEEE-1202
CSA FT 4
UL 1309/CSA, C22.2 No 245

 

[dpc]

I don't see how use of three ground conductors is going to reduce the traveling/reflected waves that cause high voltage stresses on PWM drive outputs. These are caused by characteristic impedance mismatch at cable terminations.

I will concede that this cable construction might reduce induced ground current, but I'm skeptical of that as well. If the single ground conductor is causing that much induced current, I'm not sure adding two more conductors will solve the problem. You will still have a good deal of non-symmetry in any random-lay cable.

 

[jbartos]

Suggestion to the previous posting: The cable structure/construction has some impact on the cable impedance (including positive, negative and zero sequence cable impedances)

 

[thinker]

Thanks to all who responded to my question. JBARTOS: per
your input we took closer look on marine/offshore cables.
We found a cables which perfectly fit the application. I'll
share this information: Manufacturer - AmerCable, Series
37-102VFD, Type VFD Power Cable, Gexol Insulated,2kV rated,
3 phase conductors & 3 symmetrical ground conductors, overall copper braid shield, 110 Deg.C rated, UL,CSA listed,
cable tray rated, sizes 1/0 through 777 kcmil.