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Harmonics prediction on an installation with variable speed drives.

Gareth Whitty

I have been asked by a client to provide a harmonics prediction report on an installation with variable speed drives. I have never done one or been required to look into this before. Could someone assist me with the sort of information i would need.

We are installing around 15 Variable speed drives that will control numerous pumps and agitators around the process plant.  It is a brand new facility, so at the moment I don't know the nature of the supply to the facility although i will be able to find this out soon.

The variable speed drives will range from 0.37kW and 5.5kW, 3 Phase so nothing big.

I basically need to know what sort of information I would need to obtain from the client and the VSD manufacturer, and then how I would compile that information into a report.

I assume i will need to provide a report on each drive rather than an overall report for the installation.

Any help will be greatly appreciated.

  • +1

    Are they looking at a compliance report with regards EREC G5/5? I would imagine that you're looking for a Stage 1 report which is reasonably straightforward with documents obtained from the manufacturer and supplier.

    Distribution Code Annex 1 documents - EREC G5/5

    That said there are specialists who make a living out of the more complex end of this type of work... if in doubt use them.

  • 0 in reply to Jam

    Thanks for Replying Jam,

    They haven't exactly what report they want, it is something I need to raise with them.  I appreciate the link to Annex 1 it will be a great help.

  • +1

    Hi Gareth,

    Given what you have said about the sizes of the VSD, I think an overall report for the installation would probably be the most use for the client and is probably what they need.

    From the client you need to know the existing supply details and other load details.  You may be able to gain the existing load details through some load monitoring if the site is operational.

    From the VSD supplier you need to gather information relating to harmonic currents at the operating point of the drives.  If you do not know the operating point or manufaccturer data isn't available for the particular operating point that you have then you can either work with the data that they do provide and adjust, or use the planning limit values from the EREC document, or take measurements from the drives

  • 0 in reply to chrisbryant

    Thanks Chris that is extremely helpful.

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