It is very important that VFDs are installed correctly in order to minimize interference to other equipment.
There are a number of basic rules that should be applied to the installation procedure to minimize problems and these are usually covered in the instruction manual for the VFD.

I have recently come across a number of VFD installations that are causing severe interference with flow meters and other equipment to the extent that some equipment has been damaged by the induced noise levels. These have not been installed in accordance with the manufacturers instructions.

I am looking for a simple test and/or equipment that can be used by an installer to see if the VFD installation is satisfactory. This does not need to be a full compliance test, but just a reasonable indicator that the installation is not "BAD", and that it is safe to install sensitive equipment near by.

Has anyone got any experience or suggestions?

Before reading Keith's post, my first thought also was use of a portable AM radio.  These are very handy for checking out EMI.

Nothing quantitative, but a good general indicator of stray RF.  The directional characteristics of the ferrite core antennas normally used can help a little in getting a general idea on the source of the noise as well.  

Ham radio operators often use them to track down noisy insulators, etc on power lines.  

You could baseline the noise using an installation where you are not having any issues.  I suspect even in a "good" installation, you will hear some hash in an AM radio. 

You are treading on sore toes here! And you probably know it, too!

"Static" in an AM radio is a sure sign. It is being used a lot by guys checking for bad installations in apartment houses. It is also easily understood by anyone. Switch the VFD:s off and static disappears. Easy. No discussion.

This problem is what makes me spend lots of hours on the road. (ball valve)This and bearing EDM.

I have been using a very simple circuit to detect and quantify conducted emissions for many years. It consists of a couple of blocking high-voltage, high-frequency capacitors to block off mains frequency, followed by an HF transformer that is good up to 50 MHz. There is also a 50 ohms resistor parallel to the secondary of the transformer.

With this simple circuit, I get a flat frequency response from about 20 kHz to 10 MHz. Response then drops 3 dB at just above 20 MHz and 10 dB at 30 MHz. 30 MHz is where the conducted emission standards stop.

I use this device together with an oscilloscope with FFT so that I can check for emission spectra in the range 150 kHz - 30 MHz. Very, very few installations meet the EMC directive. And there is very little to do about it. This is an official secret.

You can ask any supplier of VFD:s to show the curves for conducted emission. They will not show it to you. The reason is simply that most (I hesitate to say all, but I think that would be correct) PWM based VFD:s emit a lot more than they are allowed to. I regularly measure 20 or 30 dB above the "home, office and light industry" limits. Sometimes more than that.

Filter or no filter, the complete installation always radiates a lot more than it is allowed to. The reason is that there is no good ground plane to connect the filter drain wire to. So it is connected to the PE, which conducts the HF noise all over the building. It is a sad thing. And denied by all VFD suppliers.

There are a number of simple steps that can be taken to reduce the EMC and these are usually described in the installation manuals. They are not trade secrets although there may be some extra sneekies around as well.

The first step is to ensure that the drive has been designed with EMC in mind. If it is a bad drive, you may be able to improve things, but it will still be bad. I have worked with some drives where there was no way that we could get them to meet the EMC standards under laboratory conditions, - they were just not able to meet the spec. Drives designed for use in Europe must be designed to meet the CE requirements and this will be defined in the manual along with any special filters required in order to meet spec.
The first step, is to use a proper screened cable between the drive and the motor. There are different levels of screening and they have very different results. The best cables have a very tighlty woven copper screen (sometimes double screened) and distributed earth conductors (between the phase conductors).
Second, terminate the screen correctly at the motor AND at the drive. The correct termination is to use a screened gland of clamp to secure and bond the screen to the drive case and the motor case. Pig tail connections are very inferior and produce a much degraded performance.
Third, if there are earth conductors in the cable, take them to the earth connection on the drive and motor.
Fourth, any control cables should be screened and the screen should be earthed at one end only.
Fifth, if the manual describe or specifies input and/or output filters as necessary for CE complience, then these should be used. It is important to use the types specified for best performance.

If this is done correctly, it will significantly reduce the EMC problems and in most cases, will overcome issues.
Further improvement can be achieved by the addition of some ferrite rings on the output conductors such that the thre phase conductors pass through the ferrite rings together, and the addition of an EMC on the input will help to reduce the conducted emmissions.

Definite DO NOTs.
Do Not connect an earth from the motor back to the main earth. The only earth connection should be to the output of the drive.
Do Not bond one end only of the screen of the cable betwen the drive and the motor. Both ends must be bonded.

Installation with submersible pumps.
Run unscreend cable from the pump up to a junction box on the well head.
The well head junction box should be a metal box with the box directly mounted on and bonded to the well head.
Run a screend cable betwen the drive and the wel head box with the screen(s) bonded at the drive and the well head box. An additional large flexible cable between the well head box and the drive output earth can make an additional improvement also.

If you do the above, you will usually overcome the EMC issues. It is dificult to get the installers to do the above, most argue that you must only bond one end of the screened cable if you use a screened cable.
The best performance is limited by the installation and by the drive design.

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