VFD Cabling

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Dick, if you are getting paid to help design a vfd installation and do not spec 4 conductor shielded motor cable, then yes, you are caught with your pants down.

If you are a technician at a plant and are asked about this and you have no experience in the area and say so then suggest just 3 wires run will suffice, you are probably ok, although of course wrong.

Not sure if you are asking a question here, or just making a statement that if one is paid to engineer a vfd installation and they do not suggest 4 conductor vfd shielded cable be used, they are not doing their client justice.

BTW, Alpha makes very good cable, but their hype in the attached reference is, to some extent, well hype, about their cable being 40% vs the next best being 30% good. Of course there is good, better, best shielded cable, but that doc seems too far into our stuff is better than everyone else area IMHO. Now if they compared their 80% shield coverage to someone elses 70% coverage, etc, then they are being honest.
 
I suspect that there are a fair number of installations that would benefit from using cable like this, but that the vast majority of installations will work just fine with plain old wire an conduit.

There is just no reason to suggest every installation benefits enough from this insanely expensive stuff to use it on every VFD.

The weird thing is that it seems like a substantial number of people are running this stuff in conduit anyway, so they get to pay even more, for little benefit.

It appears to me like this is fine stranded stuff and thus requires the use of expensive connetcors on both ends.
 
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All of what you say may be true ,I'm only saying it's easy to overlook in a General Job Specification and is oft times asked for.

dick
 
dicklaxt said:
All of what you say may be true ,I'm only saying it's easy to overlook in a General Job Specification and is oft times asked for.

dick
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Very true. A lot of fads get written into specs. The people that write specs tend to copy each other and once it gets into one somewhere and seems like a "good" idea, it tends to get copied very quickly.
 
petersonra said:
I suspect that there are a fair number of installations that would benefit from using cable like this, but that the vast majority of installations will work just fine with plain old wire an conduit.
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Probably so provided no other conductors are run with it.
This is what our usual drive supplier recommends.
Symmetrical power cable equipped with concentric protection wire and intended
for the specific mains voltage
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I think the key point here, as Bob mentioned in his post, is that this cable is needed when you DON'T use steel conduit. Individual THHN conductors in properly grounded steel conduit has worked fine for years and years. The problem is, people don't do that, i.e. PVC conduit or just layed in cable Tray, or they get to a J-box near the motor with steel conduit, then run NM flex conduit to the motor. THAT is where the problems can happen and using this shielded VFD cable is necessary. But putting this cable inside of steel conduit is somewhat redundant and expensive.

Elsewhere in the world, such as the UK where Besoeker is, they don't use steel conduit as much as we do here in North America, so you will see that cable in the specifications predominantly.
 
Their is also a blurb somewhere where it states that a 4/c is not recommended but 3 phases and 3 individual grounds.I think it may have been a Southwire Publication.

dick
 
Jraef said:
Elsewhere in the world, such as the UK where Besoeker is, they don't use steel conduit as much as we do here in North America, so you will see that cable in the specifications predominantly.
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You're right. We don't use steel conduit as much. Rarely to never.
And, actually, I've never seen "VFD cable" specified.
As I've posted before, we use steel wire armoured cable for power so the issue doesn't arise here.
 
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