A practical approach to solving large drive harmonic problems at the design stage

Harmonics associated with large variable-frequency drives or large groups of smaller drives, which can create severe problems for the industrial plant´s power distribution system and the utility´s power grid, are discussed. The authors address how to eliminate the harmonic problems early in the design phase of a project and show that it is not an insurmountable task. Attention is given to the creation of harmonic specifications, the information required, harmonic reduction options, design check points, and field verifications. It is concluded that through the proper design and design checks a large electric drive can be installed that will create no harmonic problems for an industrial power system. To assure that a particular system will operate properly, it is necessary to understand basically what harmonic problems can result and design around them. A well-designed system requires that the purchaser provides to the vendor not only a complete operational specification but also some key power system information