Need Help! enclosure wiring questions 220v VFD + 110v DC power supply


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Thread: enclosure wiring questions 220v VFD + 110v DC power supply

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    Activation process thisispete's Avatar
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    Question enclosure wiring questions 220v VFD + 110v DC power supply

    I'm building DIY electronics for a 4x4 table.

    I have
    - 220v hy VFD
    - power supply that was wired for 110v (but has no specs so I don't know if it will take 220v)
    - Gecko 540

    I want to have a main power switch to the enclosure

    Is it common to run 2 separate power cables, one 220 for the VFD and one 110 for the control board, and switch them individually?

    OR

    If I have 4 wire 220 running into the enclosure (hot - hot - neutral - ground) can I switch the 2 hots using a DPST switch and pull 110v from one leg of the hot and the neutral?

    (See attached sketch)

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    Last edited by thisispete; 01-24-2019 at 06:06 PM. Reason: image is sideways


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    Member Jim Dawson's Avatar
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    Default Re: enclosure wiring questions 220v VFD + 110v DC power supply

    It's acceptable to use the 4 wire system. That's how 120V is derived in the breaker panel.

    Jim Dawson
    Sandy, Oregon, USA


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    Community Moderator Al_The_Man's Avatar
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    Default Re: enclosure wiring questions 220v VFD + 110v DC power supply

    You should also wire in suitable fusing in each of the the entry power conductors continuing to each of the destinations.
    Al..

    CNC, Mechatronics Integration and Custom Machine Design

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


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    Default Re: enclosure wiring questions 220v VFD + 110v DC power supply

    Quote Originally Posted by thisispete View Post
    I'm building DIY electronics for a 4x4 table.

    I have
    - 220v hy VFD
    - power supply that was wired for 110v (but has no specs so I don't know if it will take 220v)
    - Gecko 540

    I want to have a main power switch to the enclosure

    Is it common to run 2 separate power cables, one 220 for the VFD and one 110 for the control board, and switch them individually?

    OR

    If I have 4 wire 220 running into the enclosure (hot - hot - neutral - ground) can I switch the 2 hots using a DPST switch and pull 110v from one leg of the hot and the neutral?

    (See attached sketch)
    Your sketch is correct just add circuit breakers or fuses for each device

    You need to avoid running from to separate sources

    Mactec54


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    Default Re: enclosure wiring questions 220v VFD + 110v DC power supply

    Quote Originally Posted by mactec54 View Post
    Your sketch is correct just add circuit breakers or fuses for each device

    You need to avoid running from to separate sources
    Just out of curiosity, why avoid running your 220V and 110V from separate sources?

    I read the opposite previously. It said to power your 110V from a separate source since using one leg of your 220V could cause an imbalance that the VFD wouldn’t like.


    Sent from my iPhone using Tapatalk



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    Default Re: enclosure wiring questions 220v VFD + 110v DC power supply

    Quote Originally Posted by BrokenHorn View Post
    Just out of curiosity, why avoid running your 220V and 110V from separate sources?

    I read the opposite previously. It said to power your 110V from a separate source since using one leg of your 220V could cause an imbalance that the VFD wouldn’t like.


    Sent from my iPhone using Tapatalk
    If the wire sizes are spec'd for the load, there would be no significant voltage sag. There can be no imbalance on a 240V single phase circuit, since the voltage is measured across the two ''hot'' legs. There could be an imbalance between the hots and the neutral, but the VFD doesn't ''see'' that because the neutral is not connected to the VFD.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: enclosure wiring questions 220v VFD + 110v DC power supply

    Quote Originally Posted by Jim Dawson View Post
    If the wire sizes are spec'd for the load, there would be no significant voltage sag. There can be no imbalance on a 240V single phase circuit, since the voltage is measured across the two ''hot'' legs. There could be an imbalance between the hots and the neutral, but the VFD doesn't ''see'' that because the neutral is not connected to the VFD.
    Thanks for the clarification. So having more amp draw on one of your “hot” legs (the one going to neutral for your 110V components) won’t be an issue then? I think that’s what the other post meant by imbalance (more amp draw on one hot leg versus the other).

    If it’s already set up with the 110V components getting power from a different circuit than the 220V components there’s no harm in keeping it that way is there?



    Sent from my iPhone using Tapatalk



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    Default Re: enclosure wiring questions 220v VFD + 110v DC power supply

    Quote Originally Posted by BrokenHorn View Post
    Thanks for the clarification. So having more amp draw on one of your “hot” legs (the one going to neutral for your 110V components) won’t be an issue then? I think that’s what the other post meant by imbalance (more amp draw on one hot leg versus the other).

    If it’s already set up with the 110V components getting power from a different circuit than the 220V components there’s no harm in keeping it that way is there?



    Sent from my iPhone using Tapatalk

    As long as it's working OK there is no reason to make a change, especially in the home shop. In an industrial application I would install a 240/120 control transformer to power up needed 120V stuff, this is to provide a single point disconnect for the entire system for safety reasons.

    There are some advantages to running a seperate circuit for the 120V stuff. On my lathe for instance, the 3 phase comes off of the RPC, which supplies the drive power and 120V control voltage from a transformer. But the computer and 24V control power is supplied by a separate 120V source so the computer can be powered up without running the RPC

    Jim Dawson
    Sandy, Oregon, USA


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    Quote Originally Posted by BrokenHorn View Post
    If it’s already set up with the 110V components getting power from a different circuit than the 220V components there’s no harm in keeping it that way is there?
    Broken horn - correct my understanding is that as long as the dc control circuit for the vfd is properly isolated then there is no issue running separate sources.

    What I'm a little unclear about is grounding between AC and DC, a friend offline said not to "ground" the DC to the AC circuits. So the one that says "gnd" from the 540 to vcd should really be vdc- under the hood, and shouldn't use the real earth ground from the vfd. they probably labeled it gnd because its an isolated 10v signal circuit and not the 40vdc that the gecko runs on.



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    Default Re: enclosure wiring questions 220v VFD + 110v DC power supply

    Thanks everyone for your responses.

    I have a better understanding now.
    Learned that my 40v power supply actually has a 115 / 230 switch!



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    Default Re: enclosure wiring questions 220v VFD + 110v DC power supply

    Quote Originally Posted by thisispete View Post
    Broken horn - correct my understanding is that as long as the dc control circuit for the vfd is properly isolated then there is no issue running separate sources.

    What I'm a little unclear about is grounding between AC and DC, a friend offline said not to "ground" the DC to the AC circuits. So the one that says "gnd" from the 540 to vcd should really be vdc- under the hood, and shouldn't use the real earth ground from the vfd. they probably labeled it gnd because its an isolated 10v signal circuit and not the 40vdc that the gecko runs on.
    I have done it both ways with no problems. But if all of the grounds are connected together, they must be tied to a single point to prevent ground loops and possible imbalances in the ground circuit. The DC- in most industrial systems is earth grounded.

    Quote Originally Posted by thisispete View Post
    Thanks everyone for your responses.

    I have a better understanding now.
    Learned that my 40v power supply actually has a 115 / 230 switch!

    That being the case, I would connect to 230V and not bring in the neutral unless you need it for something else.

    Jim Dawson
    Sandy, Oregon, USA


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    Community Moderator Al_The_Man's Avatar
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    Default Re: enclosure wiring questions 220v VFD + 110v DC power supply

    Quote Originally Posted by thisispete View Post
    Broken horn - correct my understanding is that as long as the dc control circuit for the vfd is properly isolated then there is no issue running separate sources.

    What I'm a little unclear about is grounding between AC and DC, a friend offline said not to "ground" the DC to the AC circuits. So the one that says "gnd" from the 540 to vcd should really be vdc- under the hood, and shouldn't use the real earth ground from the vfd. they probably labeled it gnd because its an isolated 10v signal circuit and not the 40vdc that the gecko runs on.
    You should have one earth ground reference point, commonly known as the Star point ground, this is where the service ground and all shields etc should be connected to, there is two schools of thought over whether to reference any DC supply commons to this earth star point, one to leave every thing separate, and the second to reference all DC commons to this point where electrically possible.
    I subscribe to the latter.
    If you search here in the Forum, you will find a few posts where those having spurious noise issues have been cured on a suggestion of mine to ground these DC commons etc.
    I have used this philosophy for many decades with no problem.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

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


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