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AC Motor Control

Discussion in 'Scenery, Props, and Rigging' started by cheef, Oct 28, 2008.

  1. cheef

    cheef Member

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    I am making a turntable motor rig. It is set up to run a 5 HP motor and reduce the 1745 RPM down to 1.3 on the table. The problem is all I can do is turn it on and off with a switch. I would like to rig it up so I can ramp up and down turn it in reverse and install limit switches. The problem is that it is a 2 phase 220 volt AC motor. Does anyone have schematics on how to wire this up? It is working but I want to make it better for the performance, and to have for the future.
     
  2. soundman

    soundman Well-Known Member

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    That is not a common type of motor in the industrial world. What you want is a VFD (varible frequency drive unit) VFD work by changing the frequency of the electricity going to the motor either slowing it down or speeding it up. for example Motors > Motor Supplies > Adjustable Frequency Drive > Drive, AC,5 HP : Grainger Industrial Supply

    I have never used that mdoel but I have used a VFD made by allen bradley that works very nicely with a PLC for automation control. When you get into limit switches you will need some sort of brain unless the switch will just kill power to the drive unit which might not be the best way to go.
     
  3. cheef

    cheef Member

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    Ya I would love to use a VFD, I have in the past, the problem is the budget. The one we use to rent is no longer available. Also I have had one wired up to do this before but I would like to do it myself to save money. And I can do the programming to run limit switch, I just need the control of the motor for ramp up and down to do the rest.
     
  4. Malabaristo

    Malabaristo Active Member

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    You might find a soft starter (Wikipedia) for cheaper than a proper VFD. I've only dealt with them in passing, so I can't reccomend any particular one. Obviously, you'd still have to know something about safe wiring to make limit switches function.
     
  5. TimMiller

    TimMiller Well-Known Member

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    Check out The best way to buy industrial controls--low prices, fast shipping and superior service. They have VFD's and PLC's. You can wire limit switches up to a VFD, it just may take a little creative wiring, but it can definately be done. One thing to remember is do not use the control wiring directly off of the VFD, to run through the limit switches. You risk burning up the VFD by sending some funky voltage. (I had a VFD rep from Omeron warn me about this) What i ended up doing was running a 24V through the limit switches (in my case is was limit switches and emergency stop buttons) where you would flip a switch to on and if all limits were closed ( i had everything wired up normally closed) the switch along with all of its limits would energize the coil on a 24V relay. I had the VFD programmed and wired so that when its signal out (24V on this particular VFD) would then run through the relay's NO contact and to the common of my Forward/Stop/Reverse switch. The forward and reverse were wired to the appropriate contact on the VFD. If you would like a schematic i can send you one. This design worked very well. I now use ABB VFDs from automation direct for a much lower price than i have been able to find anywhere else.

    Also, 220 2 phase power is no longer around mostly. You would either have 220 single phase (2 hot legs) or 220 3 phase. I have never needed a VFD for a single phase motor before so i have never looked for one. All of my projects deal with 480 3 phase.
     
  6. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    As long as we're on the subject of control wiring, be sure to wire in an enable (deadman) switch into the circuit. Preferably this would be handled by a person other than and on the opposite side of the operator, thereby providing two sets of eyes who can safely watch for bodily harm and equipment danger. Additionally, at least two E-Stop switches should be provided, with their locations clearly shown to all in the vicinity.
     
  7. cheef

    cheef Member

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    That is exactly what I am looking for! Thinks Tim. If you have that schematic I would love to see it.
     
  8. Chris15

    Chris15 CBMod CB Mods Premium Member

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    OK, so us Aussies have normal power and none of this wild delta or two phase or split single phase confusion. Is the phase difference on this 2 phase being referred to 90 degrees? If so, by rights, a phase swap should cause a motor reversal.
     
  9. MaddMaxx

    MaddMaxx Member

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    Warning! Do Not try to step down the motor you have. You'll burn it up! Also: I built a 20' diameter revolve for the Naval Academy last year that was turned easily by two people manually with 10 people on it in full light...smooth and effective. Can be done if you byuild properly!
     
  10. cheef

    cheef Member

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    I actually thought of replacing the motor with a geared up crank for the stage hands to turn. It would be cheap and probably east to build. the problem with out revolve is that there is no place for a stage hand to grab the table itself with out being seen. so if I wrapped a endless cable around it I can take that off stage and connect it there.
     

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