Two Source VFD Advantage

Flexibility, Source-load can be configured Y-Δ or Δ-Y for harmonic reduction/elimination, depending upon source vector group.

a 12 pulse doesn't have filtering either, unless you spend a small fortune. In fact in the US, certain state utilities have now threaten to take users of 6 & 12 pulse drive to to federal court if they don't disconnect the drives all due to harmonics exceeding IEEE519.

Really? Never heard that. Sounds like a fear mongering urban myth started by someone trying to sell harmonic mitigation systems. The harmonics of an individual drive are inconsequential in many many circumstances, what is important to the utility is the THD at the Point of Common Coupling. If I have a single 100HP 6 pulse drive on a system with a 4000A total load, my THD at the drive could be 100% and it would not cause the PCC THD value to exceed IEEE519. How you attain reduction of the TDD at the PCC is also completely irrelevant. Threatening to force disconnection of 6 or 12 pulse drives because of their individual contribution is not something any reasonable engineer would support.

That said, I believe that 12 pulse is not worth the effort, 18 pulse is far better for only slightly more. But thats not what the OP asked.

Better yet if you have multiple drives is an Active Harmonic Filter. But again, only if NECESSARY because someone has determined that the percent of non-linear load compared to total load at the PCC warrants it.

Not my style, I speak from reading the hard evidence.

Sorry, didn't mean to imply that YOU were the one making that up, only that was the likely original source of that information. I have heard stories similar to that bandied about by salesmen bent on selling their particular solution equipment, or even consultants trying to drum up work.

I'm working on a project right now where there is a small Motor Control Center with an 800A bus filled with VFDs, every one of which is required to have a passive harmonic filter on the OUTPUT side of the VFD, ie going to the motor. Not a sine wave filter to prevent standing waves or bearing EDM damage, but a HARMONIC filter. The concept is preposterous. When I asked the Consulting Engineer why, I discovered he is an ME, but he had spoken to a rep for a line of sine wave filters who told him it was a new regulation. Pure BS...

Dear Mr.JRaef,

You are absolutely right.

DHAYANANDHAN.S

this

http://www.yaskawa.com/site/dmdrive.nsf/%28DocID%29/MHAL-6JETW2/$File/WP.AFD.02.pdf

shows the 6-pulse drive as over IEEE standards but the 12 and 18 pulse drives as meeting IEEE 519 limits.

I think you will find that is at FULL LOAD, anything below ... forget it!!