VFD with Computer Equipment
VFD with Computer Equipment
(OP)
We are installing a 50kw VFD in a laboratory environment that also includes a couple dozen computers and IEDs. The lab is a SCADA lab where we regularly test RS232 and RS485 networks. The VFD is 480V but ultimately originates from the same padmount transformer as the 120V supply (I'm not sure of the size of the padmount).
Should we be concerned with harmonic issues? Specifically, is a 50kw VFD sufficiently large to cause voltage distortion over 5%? What about RFI in the communication networks? I know the answers to these questions depend greatly on the transformer size, cable lengths, etc. but I'm interested to know if anyone else has run into problems with a similar configuration. Thanks!
Should we be concerned with harmonic issues? Specifically, is a 50kw VFD sufficiently large to cause voltage distortion over 5%? What about RFI in the communication networks? I know the answers to these questions depend greatly on the transformer size, cable lengths, etc. but I'm interested to know if anyone else has run into problems with a similar configuration. Thanks!






RE: VFD with Computer Equipment
This link has some software that migh give you a first approximation.
http://www.transcoil.com/analyzer/Analyzer.htm
But another potent source of trouble is radiated RF coming from the drive itself and especially the cable running from the drive to the motor. I would keep this feeder well away from any of your electronic gear. The motor feeder should be run in steel conduit and using shielded triplex cable. Okonite's C-L-X metal-clad cable is a good option.
RE: VFD with Computer Equipment
Per your original question: Yes a 50kW VFD can cause over 5% distortion, easily. Distortion will be a function of current demand waveform x system impedance, so you need to know both. VFD's come in many flavors; 6 pulse/12 pulse with filtered incoming sections etc. You need to know what you need.