Looking at the numbers it has to be remembered that the Ithd will increase with any form of mitigation at reduced load due to the more discontinuous nature of the input current. It is the magnitude of the harmonic currents which are important, not just the Ithd. On smaller drives without reactors Ithds of 85% and 135% for three phase and single phase drives respectively (and these add up, including the 3rd harmonic in the neutral conductor for single phase drives) are common.
The other thing to mention is that the MTE unit only guarantees the published performance if the pre-existing Vthd is not more than 0% (even a generator on no load has more than this !).
Both the MTE and Danfoss (another Lineator based copy ?) have limits on both pre-existing Vthd and voltage imbalance regarding performance where the Mirus Linetor does not. Those points are pretty importance from the practical standpoint. I believe also the Danfoss AHF is dedicated to Danfoss drives. In any case I do not see any drives company rushing to give Danfoss business where the Mirus unit is suited to the majority of VFDs with diode or SCR pre-charge front ends.
Since the tests by Toshiba were performed that have seemingly standardised on Lineator as in this and other tests Lineator often performs active filters without the cost and complexity.
I have no axe to grind re active filters as I have been involved in them since 1996. It is best that the application criteria determine the type of mitigation not just what is considered 'sexy'. Performance, price and relability are things to go for in my eyes.
ICEMAN
