harmonic measurement and calculation

[deesky]

there are some manufacturers of variable frequency drives that advertise, meeting IEEE-519, less then 5% THD on their drives. can someone please tell me where is the proper place to measure THD, the line, the neutral?
it seems to me that a typical drive will produce upwards of 30 to 40% THD, what are they doing to rectify this?
thanks in advance

Doug.

 

[electricuwe]

What size of drive are you talking about? Drives with a power of more than about 2.2 kW are usually connceted to the three phase line. In this case the neutral is usually not connected. So the THD of the input current on the line should be measured.

A good source for more information on this topic is:

Paice, Derek A.: Power Electronic Converter Harmonics, 1995, IEEE Press