Wire two devices to one VFD
Close
Login to Your Account
Likes Likes:  0
Results 1 to 6 of 6
  1. #1
    Join Date
    Feb 2005
    Location
    Posts
    17
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    0

    Post

    I bought a Mototronics VFD from surplusjohn some time ago and have finally gotten around to hooking it up to my Bridgeport. Its working fine. My question is about the power feed attached to the x axis. Apparently that is also a 3 phase device. The VFD is my only source of 3 phase power. Is it ok if I wire it into the VFD in parallel with the Bridgeport?

  2. #2
    Join Date
    Apr 2005
    Location
    SE Mich.
    Posts
    347
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    1

    Post

    Its possible but not recommended. The general rule with VFDs is one per device.

  3. #3
    Join Date
    Feb 2005
    Location
    Birmingham, AL
    Posts
    4,028
    Post Thanks / Like
    Likes (Given)
    13
    Likes (Received)
    50

    Post

    No switching downstream of the VFD recommended.
    turning your X feed on and off downstream of the VFD a bad idea. You could get a VFD for the feed, get a single phase feed, use a RPC for the feed or not use the feed. Sorry for the bad news, but thats better that than roasting your newly hooked up unit.

  4. #4
    Join Date
    Feb 2005
    Location
    Posts
    17
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    0

    Post

    > No switching downstream of the VFD recommended.

    Does that include the forward/off/reverse switch attached to the Bridgeport as well? Do I need to remove it, or will keeping it in one position suffice?

  5. #5
    Join Date
    Jan 2005
    Location
    Roseville, CA
    Posts
    3,857
    Post Thanks / Like
    Likes (Given)
    27
    Likes (Received)
    22

    Post

    Best to wire directly to the motor, so no "accidents" occur.

  6. #6
    Join Date
    Aug 2004
    Country
    UNITED STATES
    State/Province
    California
    Posts
    2,798
    Post Thanks / Like
    Likes (Given)
    30
    Likes (Received)
    699

    Post

    Best to wire directly to the motor, so no "accidents" occur.
    The VFD that is. It's OK to change the motor leads through the drum switch while the VFD is off, just not while running. Most people however use the drum switch as forward/rev inputs to the VFD, since the VFD can reverse the motor rotation without physically switching wires. All you need is to buzz out a contact that closes in each (and only in each) direction on the switch, then program the VFD to accept Forward-Reverse commands on the inputs.

    Back to your first question: If you are NOT using the VFD for speed control or reversing AND the total motor FLA is less than the VFD rating AND you have separate motor overload relays for ewach motor, then it is possible to run multiple motors from the VFD as long as they both turn on and off together, which is not the case with a feed motor. So don't do it, as others have said. It's probably a very small motor isn't it? A 1/2 HP inexpensive VFD like an FM50 or an AC Tech SCM should only be around $100 brand new.


Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •