RF/MF Drive Interference


Thread Starter

Josh Thames

Been having problems with a digital FlexPac3000 drive that we installed at the first of this year. It has been faulting (fault code is F0999), indicating RF/MF interference. It replaced an older MaxPac Plus analog DC drive, while the three remaining DC drives were converted to AC drives (GV 3000). All drives are reliance. Two of the three AC drives are on the same network with the FlexPac, which is an AutoMax drive network. I have added snubbers to all inductive loads in this section of the line, grounded everything, moved the AC motor leads into their own seperate conduits as well as the DC and even used new Anixter shielded VFD cable for the AC motors. I separated out the coax for the drive network into it's own conduit as well. Does anyone have any suggestions or seen this before? I would appreciate any info.

Hakan Ozevin

I do not know these drives especially, so what I am telling here should be taken as general ideas regardless of the drive type.

Are all the drives in the same cubicle and when this problem occurs, do the AC motors start running? Then you must consider the RFI/EMC caused from the AC drives. AC drives generate comparibly high RF disturbances compared to the DC. Try these:
1.Decrease the switching frequency of the AC drives
2. Use RFI/EMC filters for the AC drives if not existing already
3. Produce a "Faraday Cage" for the DC drive, i.e., produce a metal enclosure for it which should be connected to the ground with low resistance (I assume that that you have a good ground).
4. Check once more the EM sources in your cubicle; prefer varistor+RC combination snubber circuits to only RC ones
5. Check for the contacts of old contactors, they seem to function, but cause EM problems as well
6. Check for the shieldings of the AC motor cables; sometimes the technicians forget (!) them to connect to the ground.
7. Last one, but should be the first, try to localise the problem, i.e. disconnect everyting and start up everything one by one.

I had lots of experiences with EM and disturbances in general, so I know that finding the real problem is sometimes not easy, but dont give up. You will find it!

Good Luck

Hakan Ozevin

Nicholas J. Baranyk

While this might sound silly at first, you should see the merit of my recommendation after mulling over it a while.

Noise can crop up from a variety of sources: from standard induced noise potentials, to inexperienced personnel using Walkie-Talkies. I am concluding that you don't have people walking around using two-way portables or the like, so my recommendation is to feed each and every Drive with its own Isolation Transformer. Make sure that the Transformer is rated for V-S Drive Service ( Delta Primaries, Wye Secondaries, full-rated Neutral, High "K" Factor ).

Variable-Speed Drives aren't smart enough to doscern where the noise is emanating from, and "hash" from the AC Line will give you more fits than you can imagine. Because we are very careful to bus V-S Drives from Isolation Transformeres, we have no problems, and yes, we "mix and match" Drives frequently, so don't think that you can't run a G-Vec alongside a Flex-Pack-3000.

If you still have problems, you should contact Reliance Electric. They should be able to fix you up with a CE-compliant Mains Filter, which will be my second recommendation in the event that the Isolation Transformers don't cure your problems.

Don't think that you bought junk, either -------- you purchased, in my belief, the best V-S Equipment available: hence, my E-Mail Name. I run bunches of these animals -------- 12 Flex-Pack-3000s, 6-GV-3000/SEs ( G-Vecs ), and 19-SD-3000 4-Quad DPS Drives. They don't break, and that's why I like Reliance.

Let me know how you make out. I'll help in any way that I can, including paying you a visit ( for a reasonable fee, of course ).

Nick Baranyk
Thanks for the response. The drives are on isolation transformers already (as were the old ones), but there are no mains filters in use. I am sure the the problem is being coupled in, at least in part, via I/O into the drive. The problem occurs at two times, at a strip shear (due to coupled noise I believe), and also during run but only under certain circumstances (I'm not sure on this one yet). I know that incorrect wiring practises have a lot to do with the problem and need to be corrected before too much else can be done. The problem seems to be convincing people of the "potential and effects" of noise, at least around here. A lot of our people have a bad taste for Reliance here, mainly in my opinion, due to they have not had anyone for some time who can work on the drives/systems and so it hasn't gotten the regular attention it needed over the years. Anyway... I do appreciate the response!!! Here is my email if you like or have any further suggestions, work then home: [email protected]; [email protected] Thanks again!!!