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IndustryArena Forum > CNC Electronics > Spindles / VFD > Problem with VFD Interference
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  1. #1
    Join Date
    Jul 2010
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    64

    Problem with VFD Interference

    G'day all,

    I had a chance to plug in my 4kw Huagyang VFD and spindle, however it plays havoc with my volt/amp gauge.

    http://youtu.be/H3tMSwEr3OE

    You can see, after a couple of seconds, volt and amp goes all over the place. I have used shield VFD cable and shielded both end to AC earth. In the control box, AC earth is connected to DC low. I have disconnect it DC low and earth with no change. There is no interference any of the motors or drives. Any help would be appreciated.

    Cheers Wayne.

  2. #2
    Join Date
    Apr 2004
    Posts
    5
    Your problem may lie in your statement " I have used shield VFD cable and shielded both end to AC earth." -A shield is only connected to AC Earth at one end. If you connect both ends to Earth, it is no longer a shield, its a conductor. Having multiple grounds leads to stray voltages, as different ground points will have differing voltage levels. All earths are not equal. Try lifting your shield wires on one end, and see if your problems go away.

  3. #3
    Join Date
    Dec 2003
    Posts
    24216
    Quote Originally Posted by veeguy View Post
    ." -A shield is only connected to AC Earth at one end. If you connect both ends to Earth, it is no longer a shield, its a conductor. Having multiple grounds leads to stray voltages, as different ground points will have differing voltage levels. All earths are not equal. Try lifting your shield wires on one end, and see if your problems go away.
    Not quite true anymore, It all depends on whether equi-potential bonding and grounding has been carried out.
    Also see Ch6
    http://www.automation.siemens.com/do.../emv_r.pdf?p=1

    http://www.cnczone.com/forums/phase_...se_issues.html
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  4. #4
    Join Date
    Jan 2006
    Posts
    2985
    Are these gauges connected to analog outputs from the drive or they are connected directly to the motor leads? If they are connected to the motor leads then they don't work because they cannot handle the PWM the VFD is putting out. You can put the current meter on the input to the VFD and it will do the same job. I am not sure why you want a voltage gauge.

  5. #5
    Join Date
    Jul 2010
    Posts
    64
    Quote Originally Posted by keebler303 View Post
    Are these gauges connected to analog outputs from the drive or they are connected directly to the motor leads? If they are connected to the motor leads then they don't work because they cannot handle the PWM the VFD is putting out. You can put the current meter on the input to the VFD and it will do the same job. I am not sure why you want a voltage gauge.
    Thanks for the responses.
    More details,
    These DC meters are for the motor drives, X Y & Z. (From 3 unregulated power supplies)
    Whether I connect the spindle motor or not, this occurs.
    The VFD cable is a 4 core cable, so one wire is earth.
    I cannot measure any AC ripple on any DC wiring.
    I have one common grounding block for all wiring.
    The is only an indication fault, the motors drive flawlessly, but its driving me nuts!

    Cheers
    Wayne

  6. #6
    Join Date
    Jan 2006
    Posts
    2985
    Quote Originally Posted by wayneb View Post
    Thanks for the responses.
    More details,
    These DC meters are for the motor drives, X Y & Z. (From 3 unregulated power supplies)
    Whether I connect the spindle motor or not, this occurs.
    The VFD cable is a 4 core cable, so one wire is earth.
    I cannot measure any AC ripple on any DC wiring.
    I have one cannon grounding block for all wiring.
    The is only an indication fault, the motors drive flawlessly, but its driving me nuts!

    Cheers
    Wayne
    In that case I'd be surprised if a low pass filter did not help.
    Filter Circuits with Capacitors

  7. #7
    Join Date
    Jul 2010
    Posts
    64
    Where should I put these filters?
    On the meter inputs or VFD outputs?
    Have you seen this problem before?

    Cheers
    Wayne

  8. #8
    Join Date
    Dec 2003
    Posts
    24216
    Quote Originally Posted by keebler303 View Post
    I am not sure why you want a voltage gauge.
    I'm puzzled by this? Where and what are you monitoring?
    What drives do you have? and what controller?
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  9. #9
    Join Date
    Jul 2010
    Posts
    64
    Quote Originally Posted by Al_The_Man View Post

    I'm puzzled by this? Where and what are you monitoring?
    What drives do you have? and what controller?
    Al.
    These are my machine specs
    ESS with MB-02-V6 Bidirectional Breakout Boards (from Homann Designs)
    3 x Leadshine HBS86 (8Amp Peak) Hybrid Servo Stepper Motor Drives with Encoder feedback.
    4kW air cooled spindle (apparently)
    (X & Y axis)
    8 N⋅m (1100 oz⋅in) Leadshine Stepper motor with encoders.
    2 x 500W (63Vdc) Antec Power Supplies
    (Z axis)
    4 N⋅m (560 oz⋅in) Leadshine Stepper motor with encoders.
    1 x 400W (63Vdc) Antec Power Supplies

    I just wanted to monitor the DC volt and Amp to the motor drives.

    Cheers
    Wayne

  10. #10
    Join Date
    Jan 2006
    Posts
    2985
    Wayne

    There is no reason to monitor your power supplies. Quite unnecessary.

    Anyway, if you want to try an RC filter, it should be installed with the capacitor in parallel with the meter and the resistor in series with the meter. Like this: OMEGA ENGINEERING - Data Acquisition FAQ

    Matt

  11. #11
    Join Date
    Jul 2010
    Posts
    64
    Yep, there are properly not needed, but its my first time build from scratch. I like to know what's going on!

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