Help with components for control wiring for motor.

Discussion in 'The Projects Forum' started by dermeling, Jul 23, 2014.

  1. dermeling

    Thread Starter New Member

    Jul 23, 2014
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    So I am installing a small belt conveyor that will be driven by a 1/2 HP, 480 vac, 3ph motor. The motor info is:1/2 HP TENV 230/460V, 3Ph, 60Hz, 56C.
    I will need to start and stop the conveyor when the adjacent conveyor is started/stopped.
    I have a large MCC where I had planned to get the power (480 VAC) from that is very close to where the new conveyor will be. It has a spare bucket with a breaker of unknown size available. Looks like probably 30amp or so. I will have to confirm size.
    There should be a photo attached of the electrical schematic I came up with.
    The new conveyor motor will be located approx. 40 to 50 feet from MCC.
    My questions are these:
    Phase conductor wire size = 12ga Correct?
    Ground conductor wire size = 14ga Correct?
    How do I determine what size transformer is required? 480V primary, 120V secondary I know. Is 50 VA big enough?
    Is there a specific type/size motor starter (Contactor) I need? (120 VAC coil) I believe NEMA size 1?
    Do I need another disconnect at the conveyor control box since I have the one on the MCC already? I don't believe I do but not 100% sure.
    What size fuses do I need or how do I determine the size and type needed?
    Should I add overload contacts or is it not necessary?

    I've been maintaining/troubleshooting this type of equipment for years but new to designing new control wiring. Any help is greatly appreciated!

     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    The motor plate should have FLA shown, but the current should not require #12, you should be able to use #14 throughout, a couple of things, you DO need O/L's on the contactor, they usually come as an option, the whole contactor can be had cheap in ebay.
    The secondary could also be 12/24v if need be and obtain the contactor with the suitable coil. For 1/2 HP on 440 a 00 should suffice.
    You also need fusing on the secondary of the control transformer, 50va should be OK, you can ground one side of the secondary and only use one fuse.
    You also require a local means of disconnect if the MCC is 50ft away.
    Max.
     
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  3. inwo

    Well-Known Member

    Nov 7, 2013
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    You may need #10awg depending on the NEC 1/3 tap rule and distance from 30A breaker.

    The stop button will have to be maintained contact.

    Look for a size 00 combination starter. It will have all the things Max mentioned in one assembly.

    Disconnect/ transformer etc.
     
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  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    I use the DIN style contactors, as they are much smaller and can be DIN rail mounted if need be.
    Even the transformers come DIN mount now!
    Max.
     
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  5. williamj

    Active Member

    Sep 3, 2009
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    Does the existing conveyor control have any empty aux contacts? If it does then you can control the new conveyor contactor through that, just wire in series with the new contactor coil.

    I'm assuming that the existing conveyor control is just a motor controller and not a control panel. If there are to be future additions to be made you might want to consider replacing the motor controller with a control panel that will handle a conveyor system. Just something to think about.
     
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  6. dermeling

    Thread Starter New Member

    Jul 23, 2014
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    Thanks for all the info Max!
    I don't have the conveyor/motor yet so I will have to get all the required components once it comes in or contact the manufacturer for the nameplate data.
    I will probably buy a contactor with overloads that mount below. The kind where you put the 3 leads up into the bottom set of terminal screws.
    I need to dig a little and see how I will start and stop the conveyor as the adjacent conveyor is controlled by a VFD. I THINK there is an output from the PLC to the VFD for forward and reverse signals. It's probably a 120VAC output as this is an older machine and there is very little if any 24vdc used.
    What size fuses do I need and what determines the size?
    Would you recommend Slow Blow or Fast acting?
    To clarify my initial question about the disconnect. The existing disconnect is actually about 10ft away from where the new conveyor will be but there will be about 50ft of wire/conduit between the MCC and new conveyor motor.
     
  7. dermeling

    Thread Starter New Member

    Jul 23, 2014
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    Yes, the stop button will be a mushroom E-stop maintained push button.

    I will see if I can find a combination starter like you mentioned.
    Thank you!!
     
  8. dermeling

    Thread Starter New Member

    Jul 23, 2014
    5
    0
    William, thank you for the helpful info!!

    The existing conveyor is part of a large Cut-To-Length line and it started and stopped by push button on either the main control panel or a sub-control box I installed at the end of the conveyor. The existing conveyor is run by a VFD and the speed is controlled via dial (POT) on the main panel.
    That was my hope was to use a spare N.O. set of contacts on the main conveyor starter but like I told Max I need to investigate further because the main conveyor is run by VFD and may just get a run signal from the PLC. In which case I may be able to use that output to operate a small relay with which to start the new conveyor.
     
  9. MaxHeadRoom

    Expert

    Jul 18, 2013
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    I usually buy my contactors from ebay, my favorite is Telemecanique, they also have O/L's that clip on the bottom of the contactor, if you have a Square D supplier near you you can get any options for these.
    You will need a form a disconnect at the new motor if it is 50ft away.
    One way of maybe turning the conveyor on when the other starts is to use an output on the VFD, these can often be programmed by parameter for different VFD functions, start, up to speed etc. This would also ensure the first conv had actually started.
    If the PLC is 120vac out it would have to come down somehow for the VFD who's inputs are usually 12/24vdc and/or contact closure, so it could just be a relay.
    For that size of transformer you do not need much in the way of fusing. two on the primary one on the secondary, if grounding one side, 1amp should suffice.
    The transformer load current decides the size, the VA also affects the primary fusing.
    Max.
     
    Last edited: Jul 24, 2014
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  10. dermeling

    Thread Starter New Member

    Jul 23, 2014
    5
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    Max, that's a good idea. I did a little digging and found out that the "Run" contacts/output on the main conveyor VFD already powers a relay with available contacts that I can use to start the new conveyor. Since I'm already in that panel I can just use the 120vac that is available in there and not have to add the control transformer as well.
    Now I really just have to find my motor starter/contactor with overloads.

    Attached are the new schematic and a screen shot of the contactor I'm thinking should work.

    Your thoughts?
     
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