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The company I work with installs ventilators driven by VFD's. To save on cost of EMC cabling we use load reactors at the VFD outputs. (Other considerations for not using EMC cabling have to do with certification issues, the ventilators are used for extracting smoke caused by burning cars). The overall mentality is: just install a load reactor at the output of the VFD, and all will be fine. I wonder if this reasoning isn't too simplistic. I can for instance imagine the reactance of the load reactor resonating with capacitances in the system, so it could still pass undesired frequencies.

So, in short, is just replacing EMC cabling by a load reactor justified?

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  • \$\begingroup\$ Someone somewhere (if in the EU) might have produced a "self-certification" technical file that justifies the arguments. Have you tried asking around? \$\endgroup\$ – Andy aka Jan 17 at 11:04
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The problem running a line between a VFD and a motor (particularly if the line is long) is that the VFD PWM switching edges generate noise which can be worsened by the inductance/capacitance of the cable. A properly sized load reactor will reduce the high frequency content (slow down the rise and fall times) of the PWM. I would say that a load reactor without EMC cable would actually be preferable to an EMC cable without a load reactor.

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