Danfoss VLT AQUA Drive FC 202 Design Manual

Also see for VLT AQUA Drive FC 202: Service guide Installation guide Installation guide Operating guide Installation guide

Contents

Non-linearCurrent VoltageSystemImpedanceDisturbance toother usersContribution tosystem losses130BB541.10Illustration 3.5 Negative Effects of Harmonics3.2.7.5 Harmonic Limitation Standards andRequirementsThe requirements for harmonic limitation can be:• Application-specific requirements.• Standards that must be observed.The application-specific requirements are related to aspecific installation where there are technical reasons forlimiting the harmonics.ExampleA 250 kVA transformer with 2 110 kW motors connected issufficient, if one of the motors is connected directly onlineand the other is supplied through a frequency converter.However, the transformer is undersized if both motors arefrequency-converter supplied. Using additional means ofharmonic reduction within the installation or selecting lowharmonic drive variants makes it possible for both motorsto run with frequency converters.There are various harmonic mitigation standards,regulations, and recommendations. Different standardsapply in different geographical areas and industries. Thefollowing standards are the most common:• IEC61000-3-2• IEC61000-3-12• IEC61000-3-4• IEEE 519• G5/4See the AHF 005/010 Design Guide for specific details oneach standard.In Europe, the maximum THVD is 8% if the plant isconnected via the public grid. If the plant has its owntransformer, the limit is 10% THVD. The VLT® AQUA Driveis designed to withstand 10% THVD.3.2.7.6 Harmonic MitigationIn cases where additional harmonic suppression isrequired, Danfoss offers a wide range of mitigationequipment. These are:• 12-pulse drives• AHF filters• Low Harmonic Drives• Active FiltersThe choice of the right solution depends on severalfactors:• The grid (background distortion, mainsunbalance, resonance and type of supply(transformer/generator).• Application (load profile, number of loads andload size).• Local/national requirements/regulations (IEEE519,IEC, G5/4, etc.).• Total cost of ownership (initial cost, efficiency,maintenance, etc.).Always consider harmonic mitigation if the transformerload has a non-linear contribution of 40% or more.Danfoss offers tools for calculation of harmonics, seechapter 2.8.2 PC Software.3.2.8 Earth Leakage CurrentFollow national and local codes regarding protectiveearthing of equipment where leakage current exceeds 3.5mA.Frequency converter technology implies high frequencyswitching at high power. This generates a leakage currentin the ground connection.The earth leakage current is made up of several contri-butions and depends on various system configurations,including:• RFI filtering• Motor cable length• Motor cable screening• Frequency converter powerSystem Integration Design GuideMG20N602 Danfoss A/S © 09/2014 All rights reserved. 493 3