Multiple VFD Installation
Multiple VFD Installation
(OP)
I am designing two .75kw VFD's into an industrial control system. It will be used in the US but the design may also be shared with a sister company in England. My question is regarding the thermal magnetic breaker and EMC filter that will be in the supply lines to the inverters. Can both inverters share the same breaker and EMC filter if rated appropriately? Or, should they both have thier own breaker and filter? I've shared these components before, but would like to know what others think. Are there any code issues with this? In the US or Europe? Is it common to go this route or is it frowned upon.
Any insight greatly appreciated!!
Any insight greatly appreciated!!





RE: Multiple VFD Installation
RE: Multiple VFD Installation
RE: Multiple VFD Installation
RE: Multiple VFD Installation
If you combine the two inputs, and then try to filter, you will have twice as much noise power to get rid of and will need more attenuation in the filter.
Note, input filters are only of value if you cable between the drive and the motor in screened cable with the screen properly terminated at each end. If you run an earth wire to the motor (in addition to the screen)run it back to the drive earth, not the mains earth. The drive is the generator or source of power (and noise) for the motor. A separate earth back to the supply will greatly increase the noise level and reduce the effectiveness of the filter.
Best regards,
Mark Empson
http://www.lmphotonics.com
RE: Multiple VFD Installation
if multiple motors on one vfd
motor hp = vfd hp x 1.33
but some say
motor hp = vfd hp x 1.1
I have no problem with breakers use them all the time with vfds, use ul489 approved with an inductive trip curve. I do not see why you would want to use fuses.
one Filter can be used for both motors for the one drive, just watch the overall length of field wire to the motors. The vfd manu should point this out to you in their specs.
If your exporting to the US I would make sure all components are UL listed and the panel UL/CSA stickered if possible there before you ship. That way there is no question in any part of the country when it comes for an electrical inspection locally.
RE: Multiple VFD Installation
RE: Multiple VFD Installation
RE: Multiple VFD Installation
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If we learn from our mistakes I'm getting a great education!
RE: Multiple VFD Installation
(maybe osmosis?) Try English, wait, you are English!
(I know I am going to pay for this, but I could not resist!)
BK
RE: Multiple VFD Installation
I think it probably came from his moving (a form of osmosis) from England last year to Australia, commonly referred to as "Oz" (probably phonetically from "OZ-tralia"). Moved to Oz, Oz-mosis. Am I right Patrick?
RE: Multiple VFD Installation
scotty, not sure what you mean by me having the easiest and cost effective way? but I'm currently in India working away at 1.48am and the ol' brain is going a bit fuzzy at the moment.
Don't forget, a VFD/VSD is not actually covered by itself in the EMC Directive, it is only a component of a system (the system requires a VSD,cable and motor and possibly filters) so this is why the onus is on the installer to ensure they follow the installation guidelines correctly to ensure they meet the EMC Directive.