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VFD EMI causes Blackbox controller serial disconnect

Discussion in 'OpenBuilds Forum Help' started by Tom Lindley, Mar 18, 2020.

  1. Tom Lindley

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    I am working on bringing up a blackbox controller on a Cnc4Newbie machine. I am currently testing the integration of the VFD spindle/relay and that seems to be working fine, but with a catch. When I fire up the spindle, i lose communication with the controller. I can adjust the +10 output voltage to get the proper RPM but cannot communication with the controller. I have to power down the controller and restart.

    I read a thread about interference with the VFD signals and removed the VFD cable from the tracks. I now have the VFD running overhead with the water lines. This is a 220v spindle and the regular Chinese inverter. It does trigger the IoT relay when it powers up the spindle.

    I also have a USB filter on the computer but that didn't seem to make a difference. I plan to test manually starting the spindle today, but wanted to see if there were any glaring issues I have missed.

    Thanks!
     
  2. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
    Staff Member Moderator Project Maker Builder Resident Builder

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    VFDs put out a tonne of EMI interference
    You'll need to add some mitigation against that EMI:
    - space VFD inverter away from other electronics, ideally in a grounded metal enclosure
    - use shielded wire between inverter and spindle and space away from any other wiring
    - make sure spindle body is earthed
    - add ferrite cores on all other wiring, usb cable with ferrites will help too
    - avoid USB hubs, go as short and direct as possible

    One of the big disadvantages of a VFD over a router sadly
     
  3. Tom Lindley

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    So do you think the VFD is the root cause of this? Thanks.
     
  4. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
    Staff Member Moderator Project Maker Builder Resident Builder

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    Definately. High inductance motor, high rpm, 400hz 3 phase AC, and the chinese cost cutting all come together for a perfect storm (more expensive inverters have built in noise suppression)
     

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