CE conformity to EMC directive 2

[PaulBr]

We are OEM company. In the equipment we make we are using drives, which are carring CE mark on them. Drive manufacturer has EC declaration of conformity of these drives to the european directives. These are 480VAC, 7amp and 10amp input rating drives.
My question is about EMC directive. What happen to the emission level, when several drives are used on the machine? Does it add up? Drives are operating simultineously.
Does machine as a unit need to be tested if it is conforms to the EMC directive.
Thank you.

Paul.

 

[Skogsgurra]

Yes, they add up. But not directly. If your drives are standard drives that are not synchronized, you shall square each drive's contribution, then add the squares and take the dsquare roort of the sum.

That means that two drives with EMI level X generates sqrt(X) total emission. Four identical drives generate twice as much as a single drive.

If your level is in dB, it is a lot simpler. If one drive has EMI level Y dBuV, then two drives have Y+3 dBuV and four drives have y+6 dBuV etcetera.

Yes, if you have a machine with several drives, you need to verify the EMI level of the complete machine at the PCC (the connection to the grid) when the machine is running.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[PaulBr]

Thank you. It was very informative. You've answered all my questions.

Paul.

 

[ozmosis]

The CE mark on the drive does not mean it conforms with the EMC directive, and more particular EN61800-3. The CE mark will indicate that it meets certain LV Directive levels and possibly Machinary Directive standards but the EMC Directive covers a PDS (Power Drive System), meaning the emission and immunity levels are determined by having a VFD connected to a motor at a specific distance to ensure that specific VFD will meet the emission levels determined within the standard EN61800-3. It sounds a bit vague but the simple fact is there are a number of categories now and each category has its own levels of emissions and the category is determined by your customer telling you where it will be fitted on a pwoer distribution system; meaning, if it is connected to a public supply (as an example) and there is a possibiity of your machine causing interference to others on the network, then you need high levels of filtering.
So, having CE on the drive does not mean it complies with the EMC directive. It has to be installed (as the manf advises) to the specific environment your customer is requiring. Loosely: C1 is the highest level and requires Class B filters and screened cable and will have limits on cable lengths subject to what the VFD manf advises. C2 is slightly lower emissions (Filter class A1) but still governed by what the manf advises on cable legths etc. It goes on. Your VFD supplier should be able to advise. If they don't, get another one.
Hope this helps and not hinders.

 

[PaulBr]

The Declaration of Conformity of this manufacturer states:
product "are in conformity with provisions of the following EC Directive(s) when installed in accordance with the installation instructions contained in the product documentation:
..............
89/336/EEC EMC Directive as amended by 92/31/EEC and 93/68/EEC."
The specification in the user manual is more descriptive:
"Marked for all applicable European Directive
EMC Directive (89/336/EEC)
Emissions
EN61800-3 Adjustable Speed electrical power drive systems
Part 3
Immunity
EN61800-3 Second Environment , Restricted Distribution

 

[ozmosis]

Yes, the VFD is classed as a component of a PDS (power drive system. The EMC Directive, as mentioned in your manual, will apply to a PDS and therefore it will require to be installed as per instructions in the manual, cabled up and connected to the motor. Hence the CE mark on the drive is basically applying to other EU standards and the reponsibilitiy will be on you to follow the manf. instructions to ensure the PDS complies with the EMC Directive. If you ignore the instructions of installation then you will net meet the EMC Directive. As mentioned previously, the other side of the EMC Directive put the responsibility on you/end-user to know the environment it will be going into. This is where the C1, C2, C3 ...Classifications come in and these classifications will determine the level of filtering necessary.
2nd Environment is basically looking at C3 classification whereby the connection is more "industrial", i.e. isolated from the public network by a transformer (typically). If the machine you supply goes into the public, residential or light industrial environment, then you might need higher levels of filtering than the 'standard' supplied with the drive. Maybe C1 or C2 environemnt requiring Class A1 or even Class B filters.
Most people don't bother checking and get away with it but if you are doing it right, you need to understand both the environments your products will be going into and then the restrictions the VFD supplier will impose to allow compliance.
There isn't just one solution to complying with the EMC Directive for drives (EN61800-3), it really does depend on the installation environment. The greater chance the electrical system has of polluting the public electrical network, the higher the level of filtering is needed. The higher the level of filtering, the tighter controls on the installation and (usually) the cable lengths.
And another thing, EMC Directive is not just high frequency interference (RFI) it also covers Low frequency interference too (harmonics). If you are supplying this drive into a Public/residential/light industrial (i.e.shared power system) then the harmonic product standards will come into play, especially for the current rating of the drive you have indicated. EN61000-3-2 is the standard for products <16A, so be mindful of this.

 

[PaulBr]

Thank you ozmosis. If I understood you correctly EMC conformance of the equipment depends a lot on installation environment. As I told we are OEM. We are making more or less standard equipment. It is rellatively small (2 or 3 motors and 2 or 3 drives 3 or 5 HP each). Three phase AC power is required for these machines. But customers, who are using it are different. It may be large plant, which most likely will be in industrial or it may be small shop with the posibility of being in light industrial environment.
If in declaration of conformity we'll specify that equipment is in conformance with EMC requirement for industrial environment (basically what is drive manufacturer did) is it OK? This way responsibility is put on end user.

 

[mjl2023]

I think you may want to check with supplier of the drives a little more. From the EC website on Directive 89/336/EEC;

The former EMC Directive came into force on 1st January 1992, and replaced all existing legislation for electrical and electronic equipment concerned, including fixed installations, from 1st January 1996. It has been subject to three amendments (see also Revision of the EMC Directive) and it has been repealed by the new 2004/108/EC Directive as from 20th July 2007.

Shouldn't any new OEM equiptment be to the latest directive?

I do not have a copy so I can not compare any differences

 

[ozmosis]

PaulBr
Yes, that is one of the problems you would be faced with.
The basis of the standard is "you shall not pollute electrically the network of any other person connected to this supply". This is as far as emissions are concerned. This is where the apples-apples comes in. If you are in a steel plant and you turn a 3hp VFD on, the chances of Doris sat at home a mile away having her favourite television program interfered with will be slim if not at all. However, if her next door neighbour installed a 20Hp VFD on the same network as Doris on his lathe and switched it on, there could be a posssibility of intereference if the VFD has the same sort of filtering as it would in the steel plant. The EMC Directive is there to protect 'other users' but with the necessary level of filtering for the environment it will be installed into. In basic terms, the standard is not too bothered what happens inside the steel plant as long as it doesn't get into the public domain. However, a sensible approach is always needed to ensure you protect the integrity of your own machines to ensure they operate correctly. This is outside the EMC DIrective but possible to 'use' it to ensure good practice.
The levels of filtering are all laid out subject to the sensitivity of the environment it will be going into.

I'm afraid that in your case, the responsibility rests with you to know where the machine will be going. If it is "industrial" then you could look at certain levels of filtering to suit that environment and different for "public, Residential and Light Industrial" :typically meaning the site is on a shared LV distribution network.
Difficult when you're (I guess) in the USA and your end customer could be on the Isle of Skye.