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#222030 11/30/22 05:32 AM
Joined: Jul 2002
Posts: 8,432
Likes: 3
Trumpy Offline OP
Member
Hi Guys,
It's late here, I'm about to go to bed, but before I do, I want to shout out to all the useless
"electricians" that can't be bothered to use a simple EMC cable gland when they replace an electric motor that
quite obviously uses a screened cable.
I was awoken this morning at 4am by a customer of mine that shouted down the phone at me that a section of his plant had stopped working.
After the usual questions I went and had a look.
Now, this guy has a number of different people doing his work in various parts of the factory.
I got out there and the rotational moulding section of the plant wouldn't work at all.
The guy said to me, "We had this motor here replaced yesterday", I took one look at it and said that is the problem.
Turned the motor off and everything else started working.
It had a plastic cable gland where the supply cable went into it.
What a donkey.
If gear uses a Variable Speed Drive (VFD if you will), you have to use screened cable and glands.
If you don't, however, the HASH that comes out of them can stop adjacent equipment, the cable becomes a large antenna with all sorts of noise being radiated in all directions.
Tell your co-workers, because that is a "break-down" that should never have happened.

Has anyone here struck the same thing before?

Joined: Jul 2004
Posts: 9,788
Likes: 14
G
Member
That would usually be installed in "Greenfield" (Flexible Metal Conduit) here and the listed connectors you are required to use provide that ground path. We used shielded cables in the computer biz but there was usually a pigtail with a spade connector on it to ground the shield. Otherwise there was a provision to connect it to the EGC in the plug.


Greg Fretwell
Joined: Jul 2002
Posts: 8,432
Likes: 3
Trumpy Offline OP
Member
Greg,
And that is the thing.
With flexible "Varolex" cable, you can't pigtail things, it has to be a full 360 degree screen contact to the plate inside the VSD and then bond the extra earth conductors in the flex to that plate.
Different VSD manufacturers have different ideas on screening and what-not. crazy
If you do it wrong or the last guy did, they pretty much hang up the phone on you when you need answers.
After all this time, I'd like to think I know how things should be done.


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