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Thread: Suitable relay for three wire control on a VFD

  1. #1

    Suitable relay for three wire control on a VFD

    Hello folks
    I have been walking through the steps with another forum member on setting up a VFD for his saw.
    Unfortunately the VFD does not have a relay OR COMMON for three wire control/push button station.
    Can any of you guys point me in the right direction to find a suitable relay for him?

    Any help would be much appreciated.

    Many thanks in advance.
    Tom
    Last edited by Tom Trees; 10-11-2019 at 8:21 PM. Reason: Common, or reset is the part I need in between NC and NO button station

  2. #2
    Hello again
    Guessing maybe I'm not being specific enough, as I have asked this question before for my own VFD's in passing with no response.

    I am not looking for a relay to isolate the supply.
    This is for a home workshop, not for a business, so the need for the 10 second machine stop and isolated rule does not apply.
    The VFD is in an enclosed hefty cabinet so dust or damage won't be a factor in the decision.

    It is merely for between a NO start push button and a NC stop push button.
    It is for a tablesaw, so I have advised him that it was safer to have a hands free paddle switch for his stop button, rather than two wire control using a toggle switch
    He has made a paddle for his buttons already.

    Hope this clears things up a bit.
    Sorry for any confusion or vagueness.
    I have an in-built relay on my VFD, so I have no experience with this.
    Thanks again
    Tom

  3. #3
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    What current and voltage rating? Solid state or mechanical?
    David

  4. #4

    Smile

    Quote Originally Posted by David Buchhauser View Post
    What current and voltage rating? Solid state or mechanical?
    David
    Thanks for your response David
    I think the VFD has 12v terminals, but I'm unsure TBH.
    And I don't know what I need regarding solid state or mechanical.

    I'd imagine that most VFD's have the same voltage output for external switch controls.

    My VFD is the same as the one my mate has, but his relay does not work from the get-go.
    My relay failed upon swapping my VFD over to the tablesaw (for no reason whatsoever I might add) as I wanted three wire control on it.
    It got no abuse during the long voyage... 6 feet away from the bandsaw.

    No problem as I had an older one the same so just swapped out the front panel and it works flawlessly.
    Seems a problem with the new batch of Huanyangs.


    I bought a newer VFD with auto shutoff fan control to put onto the bandsaw,
    and works via two wire control with a simple toggle switch.

    Here's what my setup was on the bandsaw.
    It seems strange to me, that its not a straight up answer, as I believe the Teco FM50 needs a relay also for three wire control for a push button station.
    Here's some pictures, in hope that it may clear things up a bit.
    If not I can disassemble my old Huanyang that got fried from the motor stalling and give you a more in-depth look at it.
    It is the newer batch of them, so will definitely be exactly the same as my friends one.

    As you can see I'm using bog standard push buttons, and the relay goes in-between into that RST terminal (nothing to do with the RST mains 230v input terminals)


    DSCN2230.jpgDSCN2205.jpg

    I'm gonna guess this might be the most useless information ever, that I'm giving you.
    I hope you are not frustrated by my lack of knowledge.

    Awaiting a scolding
    Thanks
    Tom
    Last edited by Tom Trees; 10-12-2019 at 3:45 AM.

  5. #5
    Looking at the manual now, and it states no additional information on the voltage or anything else is relating to the multi input control circuit terminals.
    This RST relay terminal is titled as reset, FOR is forward, and DCM is described as common terminal of digital and control signals.

    Surely there are folks using a Teco FM50 or similar on a tablesaw or spindle moulder etc, and have hands free off switches and not using a toggle switch?

    Are you all doin the Holmgren paddle?

  6. #6
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    https://www.factorymation.com/22PBA2-N4P-200-00

    This is a simple contactor with the green button normally open (NO) and the red normally closed (NC). It's what the TECO expects. You need 3 wires from the VFD to the box: common, start, stop. The voltage is low, 12V I think. I used some leftover telephone cord (old, old leftover, four wire red/green/yellow/black), just about anything will work.

    I don't have a photo handy, but my tablesaw I have two 4x6 paddles and a 'finger' on a common rod that goes from left to right just under the fence, the wooden finger just touches the stop button. I don't have to look to slap one of the paddles -- left hand or right -- and shut off the saw.

    For a second saw I have a simple off/on switch, but it's a red mushroom: pull for on, push for off. I don't have to look for that either, but it is smaller.

    Terry T.

  7. #7
    So you're saying the Teco actually has what I'm calling a relay?

    What you're calling a common is what I need.

    Should I edit my post and change the word relay with common, or is a relay also called a common?

    I thought the Teco FM50 needed one for three wire control, but I'm obviously mistaken, I shall edit my title, and a few bits.
    One step closer
    Thanks Terry
    Tom

  8. #8
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    Quote Originally Posted by Tom Trees View Post
    So you're saying the Teco actually has what I'm calling a relay?

    What you're calling a common is what I need.

    Should I edit my post and change the word relay with common, or is a relay also called a common?

    I thought the Teco FM50 needed one for three wire control, but I'm obviously mistaken, I shall edit my title, and a few bits.
    One step closer
    Thanks Terry
    Tom
    Here is a solid state relay. It can be controlled by a DC voltage between 4 and 32 volts. It is used to switch an AC voltage (on or off). It has a maximum current rating of 50 Amps. I would need to see the schematic or wiring diagram of what you are trying to achieve in order to provide any more useful input.
    David
    (Electrical Engineer)


    https://www.alliedelec.com/product/i...-50a/70174931/

    solid state relay.jpg

  9. #9
    Thanks David
    I could give you a schematic but the picture is as helpful as it.
    The part I'm after should only be the price of a pint of beer, as its on a cheapo VFD.

    What happens without this component is, one has to keep their finger held on the push button switch for the motor to run, take your finger off and it stops.
    To explain this, I will break it down in the simplest way I can, which is the bog standard test for wiring switchgear on an VFD/inverter, (its what the pro's do)
    Normally folks use short wires and figure out the configuration like this.

    Forgetting the switches for the minute, one can do the same thing with short wires on this VFD I have.

    All one needs to do the test is have 4 short wires
    1 wire in FOR, 1 wire in DCM, and 2 wires crammed in RST.

    Twist or hook the DCM wire with one of the two RST "Common" wires.
    FOR can be struck off the other RST "Common" the motor runs. (the FOR just needed to be struck momentarily and is not connected to anything)

    To stop the motor unhook/separate the DCM with the other RST "Common"

    It's that simple.
    If I can just find the part as there's no information about this "common"
    Probably the worst name it could be possibly called if ones searching that into Google

    Any help appreciated to source this cheapo part.
    As said, I can open it up as I have a spare drive if anyone's interested.
    Way over my head, but someone may find it interesting.

    Thanks again
    Tom
    Last edited by Tom Trees; 10-11-2019 at 10:47 PM.

  10. #10
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    I just use a $10 powermatic paddle switch. With one wire to run, one to ground/common. Sure it's a 20 amp 240 rated switch but it's what I had. A tiny toggle switch will do the same. It essentially functions like a light switch or toggle switch but it has a button for start and a button(paddle) for stop.

    Ground/common is often referenced, in describing switches and buttons as they will operate in several ways. For low voltage stuff like this they may be pull up or pull down where you essentially will either short the terminal to VCC (maybe 5 or 12V) or ground(or common) the controller will read this change of state, its not exactly like a light switch in some cases, but its still a switch.

    It looks like in your case you can use any normal on/off maintaining switch between DCM and FOR.
    Last edited by Steven Cooper2; 10-11-2019 at 11:35 PM.

  11. #11
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    The FM50 doesn't need an external relay for three-wire control. I borrowed this illustration from OWWM:

    IMG_1137.JPG
    Chuck Taylor

  12. #12
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    Quote Originally Posted by Charles Taylor View Post
    The FM50 doesn't need an external relay for three-wire control. I borrowed this illustration from OWWM:

    IMG_1137.JPG
    Per the schematic, you need a normally closed momentary switch and a normally open momentary switch. The part previously cited looks like it would work, but is more expensive.
    https://www.factorymation.com/22PBA2-N4P-200-00

    Here are several from Amazon that are pretty inexpensive and should work fine as long as you have a way to mount them.

    https://www.amazon.com/SPST-NORMALLY...=fsclp_pl_dp_2

    https://www.amazon.com/SPST-BUTTON-S.../dp/B006M4ZGOI

    You can search Amazon or Ebay to try to find a matched pair if cosmetics is important and you want them to look the same.

    David

  13. #13
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  14. #14
    So by what you guys are saying, it's not just a common part my friend needs to have three wire control, using momentary switches like my friend and I already have...
    and it has to be two wire control, with a sturdy permanent switch type like a heavy duty light switch or toggle type,
    so he has no option but to do the Holmgren paddle.

    I don't think he will be pleased after making a paddle system for the momentary type.

    Still if anyone is wondering on why the "common" is faulty on my Huanyang VFD, and the one my friend has, I would be more than happy to
    "inspect" the one that I swapped over to my spare parts drive.
    I don't have much more than a basic multimeter, but I can take a video, or pictures of it if anyone is interested.
    I did work well for a few months, so it's not like the part was omitted.
    I don't fancy swapping the front panel back to the working drive though, for fear that this one might forget the "common" component.
    It's on a tablesaw as well, and with a paddle system like I told my friend to make.
    I think its a good bit safer than the Holmgren type, as if some stranger tried to turn it on, they would have to figure out that you can't touch the paddle
    when poking your finger through the hole to press the NO momentary on button.
    It's very sensitive, so you couldn't be wearing a heavy glove to turn it on.
    IMG_20170421_101613.jpgSAM_2105.jpg

    Tom
    Last edited by Tom Trees; 10-12-2019 at 3:35 AM.

  15. #15
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    Are you using the VFD for a phase converter? In other words, does the saw have a 3 phase motor and you are wanting to run it from 240Vac single phase power? Otherwise, I'm not really sure why you would want variable speed on a table saw. I have a 4HP 3 phase belt sander that I am running on 240Vac single phase using a 5HP VFD. This also gives me variable speed control which is nice for this application. The VFD has a button on the front that I push to turn the motor on or off and a knob to adjust the speed. My setup doesn't use any relays or other external momentary switches. I don't normally wear any gloves when using my table saws.
    David

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