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VFDs, Harmonics, and long, long runs

VFDs, Harmonics, and long, long runs

VFDs, Harmonics, and long, long runs

(OP)
We are using some 12 and some 18 pulse drives on 4160v motors. The motors are fairly close to the VFDs. The point on common coupling (PCC) is locate approximately 2 miles away from the VFDs.

Can harmonics flowing back to the PCC 2 miles away have an impact on the distribution line?

Thanks.
b

RE: VFDs, Harmonics, and long, long runs

Theoretically, yes.  The two miles represents a certainly level of buffering impedance that will tend to reduce harmonics.  But not as much impedance as a transformer or reactor.  

But it unlikely that you will have issues with a 12-pulse drive and extremely unlikely you will issues with an 18-pulse drive.  

A predicted harmonic level can be calculated.  And harmonics can be measured at the PCC.   

David Castor
www.cvoes.com

RE: VFDs, Harmonics, and long, long runs

(OP)
With higher impedance in the line, i woudl assume a higher voltage drop along the line would would result in heating of the cable?

I was thinking there would be a concern with capacitance with such a long run and the harmonics.

RE: VFDs, Harmonics, and long, long runs

As David said, not much harmonics with 12 and 18 pulse drives. And, the heating will not be higher with a long cable simply because the possible increase in losses is distributed along the longer cable. Watts/mile stays more or less constant.

If the motor cables were long, that would be another thing. But they are not.

Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

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