Reversing Switch Wiring 3Phase Motor

Discussion in 'Machine Modifications' started by rickhann, Feb 24, 2018.

  1. Feb 24, 2018 #1

    rickhann

    rickhann

    rickhann

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    I have a small VFD controlled 3 phase 1/4 HP motor running my lathe. I purchased a YMW26-25/4 switch from Banggood that I would like to use to provide the capability to reverse the motor. I would like to install it between the VFD and the motor. There was no wiring diagram included with the switch, but I found the switch configuration by googling the switch model number. I am still unsure as to how to connect it as I am not an electrician. I have attached the switch configuration. Any help would be greatly appreciated. I am assuming it can be done. Thanks
    Rick

    Screen Shot 2018-02-23 at 8.27.26 AM.png
     
  2. Feb 24, 2018 #2

    bruedney

    bruedney

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    It is my understanding that it is recommended that NO switch be placed between VFD and Motor as serious damage can happen to the VFD unit. All the VFD's that I have looked at can reverse direction on the fly so why would you need a switch anyway?
     
  3. Feb 24, 2018 #3

    BillH

    BillH

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    I let my VFD do the reversing with a single pole, double throw switch sending the appropriate signal to the VFD. However, for the purpose of this discussion, if these motors are just like my brushless DC motors for r/c, you should only need to swap two of the three legs for reverse. This is probably what the VFD does internally.
     
  4. Feb 24, 2018 #4

    rklopp

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    Accordingly, it looks like you could hook up contacts 1-2 for the forward low-voltage CONTROL input and 3-4 as the reverse CONTROL input on your VFD. My guess is that 1 and 3 would share the Common terminal, 2 would go to the forward input and 4 would go to the reverse input. Study the manual.
     
  5. Feb 24, 2018 #5

    Aerofourcycle

    Aerofourcycle

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    We switch the leads after the VFD a lot. It's the leads going to a VFD that can be critical. A CT current transformer monitors the power coming in for all three phases.
    If you connect L1 to 1 and 3
    L2 to 5 and 7
    L3 to 9 and 11
    And
    T1 to 2 and 6
    T2 to 4 and 8
    T3 to 10 and 12
    T3 will stay the same but T1 and T2 will switch.
     
  6. Feb 24, 2018 #6

    rickhann

    rickhann

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    Thanks for the responses. I guess I should have been clearer with my description. My VFD has 120 volt single phase input with 220 3 phase output, so I don't know how to put a reversing switch ahead of the VFD. It seems to me that Aerofourcycle's information will work. Rick
     
  7. Feb 24, 2018 #7

    MachineTom

    MachineTom

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    A vfd has a number of low voltage connections that can control all sorts of conditions
    Look at the manual for that model. It is nice to have some low voltage switches
    controlling the
    Direction, speed, and braking, Accel and Deccl.
    Unfortunately some manuals are poorly written, leading to owner fustration.
     
  8. Feb 26, 2018 #8

    Wizard69

    Wizard69

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    Lots of things in life can be done, however it doesn't mean you should do so.

    The vast majority of VFDs sold are already configured to support reversing the motor electronically. This normally requires a toggle or selector switch tied to a predefined input. Sometime it is easier to use a supplied "remote panel" that the drives designers sell.

    You want to use the supported reversing method because modern drives offer features that help protect the motor in their use. It is also commonly cheaper to use low cost switches. Further an operating panel can be built close to the headstock with the rest of the electronics sitting in a control panel.

     
  9. Feb 26, 2018 #9

    BillH

    BillH

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    What mode are you using the VFD? Simply as a phase converter? Or are you using it for the variable frequency speed control, and maybe even a vector drive? I most certainly would not do anything with the input or output of the VFD, and allow the VFD to control direction, starting, and stopping. The only time I might consider what you are doing is if I was using it as a pure phase converter with a fixed 60hz output, and I had multiple 3 phase motors that needed to run off of it, and ONLY if the manual said it was ok.
     
  10. Feb 27, 2018 #10

    fcheslop

    fcheslop

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    Personally I would use the vfd to control direction .Its a few years since I retired and things move on rapidly but Iv not seen the set up you are planning on doing. The switch as drawn will work but switching this way can shorten the life of the VFD
    If its a Mitsi vfd then STF and STR are the terminals you need for Omron I think its terminals 1 and 2 but check in the book for youre vfd
    best wishes
    frazer
     
  11. Feb 27, 2018 #11

    rickhann

    rickhann

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    I am a perfect example of having a bit of knowledge being a dangerous thing. At least now, I know what I don't know. My VFD is a FUJI AF-300 Mini with 120V, 1ph input with 230V 3ph output operating a 1/4 HP motor. I picked both the VFD and the motor up at a Cabin Fever Show several years back. I connected them and they worked! I was happy until now. Thanks to those of you who have educated me a bit on VFD's. I have the manual and will see what I can come up with. Hopefully no "magic smoke".
    Rick
     
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