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Vacon Frequency Drive - 37KW

12/19/2016 4:59 AM

we have Vacon Frequency Drive 37kw which was working fine but lately it was tripping the PLC. we suspect that the issue was due to harmonics coming from the VFD which was causing the plc to trip. Also, We shielded the control cables with the Earth.

We thought the issue might be with the VFD so we changed it too. The tripping is reduced after we did all the above things.

I want to know if we can provide any filter in the VFD so that this issue is stopped completely.

Kindly help in this regards i really appreciate it.

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#1

Re: VACON FREQUENCY DRIVE - 37KW

12/19/2016 5:14 AM

These people can help.

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#2
In reply to #1

Re: VACON FREQUENCY DRIVE - 37KW

12/19/2016 6:40 AM

It is not easy or simple to use tech support in companies like this. They usually want a fat pipe into your cash flow. Often they want to send staff to inspect and bring your 'neglected installation' up to date etc.

Often installations can be repaired by a shut down and thorough clean and seal of all current carrying pathways, which have often degraded over years to increase resistance etc.

Better do this yourself instead of paying someone $1000/day per person, plus expenses, to do this.

Secondly, look for an experienced VACOn repair person who might offer better rates.

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#3
In reply to #2

Re: VACON FREQUENCY DRIVE - 37KW

12/19/2016 7:19 AM

The original poster gives no information on the remaining product warranty, nor what steps have been taken to derive Technical Support during that period. The original poster gives no information on what product support leverage is available at the facility with a view to deriving support or facing loss of future sales.

The remaining invitations are declined, as there is no Vacon drive installed here.

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#5
In reply to #3

Re: VACON FREQUENCY DRIVE - 37KW

12/19/2016 7:43 AM

I assumed he does not use the phone for help option because he encountered a financial thicket that he lacked the ability to spend past.

It is axiomatic to call the maker, sadly, all such expertise, after initial warranty, often comes at a large cost, especially in other countries, and thus have a huge incentive to fix it themselves. They may, in fact, be hoist on their own petard, having represented themselves up to the task.?

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#4

Re: Vacon Frequency Drive - 37KW

12/19/2016 7:42 AM

This is a classic equipment protection system (EPS) interlock problem. The EPS is probably not failing when it trips and prevents your good equipment from running. The EPS system is probably detecting a subtle failure in your equipment and preventing it from becoming a major failure in your equipment. Examine the alarm codes presented by your EPS (you've not identified these to us) and fix your ailing equipment. If somebody dislikes the cost of this new repair (and previous attempts) then test equipment monitoring the same signals (current, voltage and time) the EPS uses to monitor the equipment. This method can identify if the EPS or the equipment is failing. Fix accordingly.

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#6

Re: Vacon Frequency Drive - 37KW

12/19/2016 8:44 AM

What PLC make and model, and what fault code(s) does it show?

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#7

Re: Vacon Frequency Drive - 37KW

12/19/2016 11:26 AM

This sounds like a typical hardware (EMC) problem to me.

Since you are not providing a detailed information of your installation and probably hardly anyone would be interested in working hard in your behalf, I recommend you any of the following.

  1. Contact an EMC consultancy company and ask them to solve it for you.
  2. Learn EMC Engineering. Henry Ott has a great book about it!

Regards.

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#8

Re: Vacon Frequency Drive - 37KW

12/19/2016 4:33 PM

This: vacon manual

10 Fault tracing 148

10.1 Resetting a fault 148

10.2 Fault codes 150

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#9

Re: Vacon Frequency Drive - 37KW

12/20/2016 3:04 AM

Why do you suspect the VFD, for causing the tripping of the PLC?

You ask about adding filtering for the VFD. Has it not been installed as per the specification in the technical manual?

Can you supply us with an Electrical Schematic of the VFD installation?

Can you identify any changes to your installation; not just with the VFD, but with the PLC; that coincides with the problems you're experiencing?

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#10

Re: Vacon Frequency Drive - 37KW

12/20/2016 4:27 AM

You said...
'we suspect that the issue was due to harmonics coming from the VFD'

Have you proved it? If not, then do so!

Call the vendors/manufacturers for both items of equipment, and tell them what you've told us, and as it's their equipment, they will be better placed to advise.
Have you done that yet? If not why not?

Yes there are filters to reduce VFD harmonic output, but again you should contact the VFD vendor/manufacturer for expert help and guidance. But adding filters goes back to my previous point, do you have harmonics?

The overall point here is that your problem cannot be solved in this forum! We can only give you pointers as to what it MIGHT be, or who to contact, or where to look.

Reading the previous posts you've had all that.. follow the advice!

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#11

Re: Vacon Frequency Drive - 37KW

12/20/2016 8:28 AM

If the problem goes away when the Vacon is switched off, then you have a cable or motor fault. It is unlikely that a sudden power supply problem with the PLC (assuming a general failure = trip?) is an installation design problem.

It would be helpful to have more detail on trip, what exactly does than mean?

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#12
In reply to #11

Re: Vacon Frequency Drive - 37KW

12/20/2016 11:51 AM

Make sure the PLC control wiring is isolated from the VFD motor wiring.

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#13

Re: Vacon Frequency Drive - 37KW

12/20/2016 1:16 PM

A common filter used with VFD's to limit harmonics is called a line reactor. It is basically an inductor and it will throw off some heat, so where it is mounted is important to consider as well. They are typically 3% to 5% reactive (relative to your load) and are in series with your VFD.

Look up Control Electronics magazine and search for electrical noise. Read the article.

Make sure your PLC power supply is not running at full capacity. Too many people do that and the inrush current of some connected device will "trip out" the PLC.

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#14

Re: Vacon Frequency Drive - 37KW

12/21/2016 1:51 PM

I'm curious how a PLC 'trips'.

PLCs are designed to run continuously. What does a PLC trip look like in this case?

Does the PLC flash a fault code and the CPU refuses to execute?

Does the fuse to the PLC power supply blow?

Or some other manifestation?

What do you do to get your PLC out of "tripped state"?

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#15
In reply to #14

Re: Vacon Frequency Drive - 37KW

12/21/2016 3:44 PM

RFI if high enough signal could disrupt connections to the PLC communications with local panels (depending on what is present on site), and the PLC might then "trip" by losing communication hand-shake, or so I believe.

Ground loop potentials if large enough could cause signal error and trip the machine (not really the PLC).

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#16
In reply to #14

Re: Vacon Frequency Drive - 37KW

12/22/2016 12:37 PM

I suppose that term is truly too ambiguous but I think the following description could fit the term.

A machine built by an automation vendor was installed after verification and it ran for about a year without incident. Then it started to drop out and rebooting part way through a program cycle at the same point when several outputs were activated at the same time. Watching the PLC, all of the little lights would briefly turn off at just this part of the cycle and then it would start up all over again without completing its cycle.

Of course, none of the fuses or circuit breakers were affected and all of the other lights stayed on. Monitoring the current to the PLC revealed that the current at the beginning of the cycle was just under the rated current of the power supply.

Of course, the vendor protested that, "Hey, it worked for a year!" Oh, and no fault code came up. If it had been my project, it never would have happened. A larger power supply solved the problem.

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#17

Re: Vacon Frequency Drive - 37KW

01/23/2017 7:29 AM
  1. Does "the PLC" have any function tied to VFD? Or is PLC concerned with completely separate function?
  2. What is physical distance between VFD and PLC?
  3. Do PLC and VFD have any shared cable trays or ducts in which transfer of Electro-magnetic Interference (EMI) can occur? Separation is more effective than screening.
  4. If changing VFD reduced trouble, have you considered that you may have fixed only one end of a corroded earth bonding or deterioration from what was OK when plant was new?
  5. Are supplies (and EMI) shared between VFD and PLC? If this is the problem, a filter in PLC supply is cheaper & easier than in VFD supply - but it will not work if cables from filter to PLC PSU share a loom/duct with other cables.
  6. Have you checked the PLC Processor PSU is all OK, free of abnormal voltage outputs or ripple indicating out-of-spec vulnerability to voltage dips or EMI? Changing load by disconnecting racks or adding resistive load is suggested.

I would suggest pulling any PLC power input cables or rack-rack power or comms cables out of any trays/ducts looms they share with other cables to give as much physical separation from other cables/magnetic fields as possible. Panel builders are fine at making things "tidy", but often do it without thought to EMI. Unless watched, they can loom up the output of those signal isolating devices (designer thoughtfully provided) with anything convenient.

Any PLC AC input filter you fit must have its earth connected to PLC PSU earth terminal by shortest practical wire.

Wires loomed or trayed together finish up with the same RFI voltages due to capacitance and magnetic coupling.

It may be more difficult/costly to put right, but any close proximity between VFD cables and other cables is bad. Wires directly from VFD to PLC are suspect as a "most likely" EMI route.

Power supplies do not care much about harmonics, most nowadays have rectifiers with reservoir capacitors & switching regulators which make plenty of harmonics anyhow.

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#18
In reply to #17

Re: Vacon Frequency Drive - 37KW

01/23/2017 9:15 AM

Interesting. I have also wondered about cable trays carrying both signal wiring and power cabling where VFD's are active.

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