Mounting VFD and Wiring Questions
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  1. #1
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    Default Mounting VFD and Wiring Questions

    I have not read all the fine print in my TECO L510 manual but from what I gather the VFD needs to be wired directly to the motor. This is different than what I had planned. I wanted to run the lathe the way it had been run for 80 years with the power coming to the switch and the old Westinghouse De-Ion emergency breaker between the switch and the motor. I guess I can handle having the switch as the controller for the VFD but I want to do the wiring smart!

    Do you guys recommend housing the VFD in a NEMA enclosure? If yes any specific type or ones I should bee thinking about?

    The electric grid out here is often spotty and we get all kinds of electrical spikes and power outages because of the energy of the Pacific storms and the poor condition of our lines. What should I be thinking about doing to protect my machine and or VFD if the VFD takes a hit?

    I also may want to add an emergency stop button. If I do where in the wiring plan would it go? Before VFD to cut the 2 phase input power or after the VFD to cut the 3 phase output power to the machine?

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    More food for thought from the manual. Do you guys put all this stuff in your circuits?

    wiring.jpg
    I have some questions about these...

    I am assuming the molded circuit breaker is my Fuse panel breaker yeah?

    Do I need a magnetic contactor if I am using a vintage drum switch as the VFD external control?

    I shouldnt need an AC reactor right?

    Is the Fast Acting Fuse for use with the AC reactor or do I need this?

    Thanks for any help or guidance.

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    Hi,

    Some answers but you should make sure you’re qualified to wire this up safely.

    I generally use fuses on the input rated appropriately for the VFD inputs. Midget fuses, one per hot input.

    Ground is wired to the VFD ground.

    I put everything in a NEMA enclosure sized generously. I have several VFDs up to 5hp in these. The last one I used is fairly big for two VFDs: Saginaw part number SCE-14128CHNF. These guys also sell a sub panel that mounts inside and is removable.

    I use a contactor between the fuse and VFD to ensure the VFD is only turned on when intended, and isolated from main power when not powered up. But this is NOT how you would control the VFD operation— use the low voltage inputs for that, including estop.

    Use a 240v to 24v control transformer to power any buttons or controls needed that aren’t powered off the VFD, including the contactor.

    I use 22mm pushbuttons.

    If you want to use external drum switch, just rewire to 24v low voltage control wires to the VFD for forward/reverse etc.

    Phil

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    Quote Originally Posted by Brandenberger View Post
    Hi,

    Some answers but you should make sure you’re qualified to wire this up safely.

    I generally use fuses on the input rated appropriately for the VFD inputs. Midget fuses, one per hot input.

    Ground is wired to the VFD ground.

    I put everything in a NEMA enclosure sized generously. I have several VFDs up to 5hp in these. The last one I used is fairly big for two VFDs: Saginaw part number SCE-14128CHNF. These guys also sell a sub panel that mounts inside and is removable.

    I use a contactor between the fuse and VFD to ensure the VFD is only turned on when intended, and isolated from main power when not powered up. But this is NOT how you would control the VFD operation— use the low voltage inputs for that, including estop.

    Use a 240v to 24v control transformer to power any buttons or controls needed that aren’t powered off the VFD, including the contactor.

    I use 22mm pushbuttons.

    If you want to use external drum switch, just rewire to 24v low voltage control wires to the VFD for forward/reverse etc.

    Phil
    Thanks for the feedback. I am not the electrical guy who will make the tie in connections but I wanted to plan the thing out and learn a bit along the way. I can do basic wiring and conduit routing and I want the whole thing to look good! I am confident I can wire and program the VFD but there are a lot of things that are confusing as I dig in and do the early prep work.


    EDIT: I found a helpful video that relates to my situation and brand of VFD so looks like I have some planning to do and some more stuff to buy.



    Ironically I would call all of this stuff, I need to use the VFD as shown in the manual, "accessories" but Marshall Wolf where I got it from apparently didn't think so. They show nothing extra that is required to use the VFD per the manual. If anyone knows a better electrical supply house maybe on the west coast please let me know. Thanks

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    You do not need an AC reactor and probably can omit the noise filters. Typically you put a power switch at the VFD enclosure to turn the system off, followed by fusing. On smaller VFDs I typically use CC fast blow fuses, the rating is outlined in the manual for the specific model. The ratings are often the maximum fuse size, and you can get by by a smaller rating as needed.

    VFDs are made to be directly connected to the motor, they protect the motor through the VFD. That is how they are designed and how they should be used in this setting. As much as people like to use the "old" drum switch, they do not handle low control voltages for the VFD inputs and I have had issues with poor connections in particular with older switch gear being retrofitted. I also do not recommend directly connecting 2 wire control directly to a switch as the machine can easily start turning when powered up after an outage. Most VFDs do have programming which will prevent the VFD restart if a run control is active at power up. Some people use a latching contactor on the input power, so if power is lost the machine will not turn on when the power comes back on.

    The L510 is a bit marginal for a lathe, as it doesn't allow the use of an external braking resistor on the 240V models, not that you can brake an older machine too quickly. The other issue is using a VFD with an older motor, you need to be a bit more conservative on some of the motor parameters.

    Wolf Automation is good for a starting point getting into VFDs, I would also look at Automation Direct. Shipping is free over $50, so can save you a bit in particular with the larger enclosures.

    On the E-Stop, there are different approaches depending on if you want to stop the machine and keep the VFD functional, i.e. brake to a quick stop (disconnect the run command), or your intent is to deactivate the VFD, in which case you can use the E-Stop to deactivate the input contactor.


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