The best way to address specification and harmonic limits is to do a proper analysis of your power system to establish a base line value of the harmonics presently on the power system at the point of common coupling, (PCC). Once that value is found, a proper solution can be formulated for your facility. For specifications that state a specific value at the drive or filter terminals, typically provide a harmonic filter that will meet the limits of most power quality specifications. Most industry power quality people today rely on the committee studies and findings of IEEE/IEC. The guideline that IEEE/IEC established is their standard 519. Most drive-applied harmonic filters are capable of achieving the standard when the customer evaluates the harmonic content at the point of the drive or filter terminals. This standard has reached an industry wide level of acceptance, and most power quality Engineers will reference this standard and openly accept the performance of harmonic or low pass filters for drive applied applications. For additional information of IEEE/IEC -519 requirements please consult the standards references.