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Power distribution and chain motor questions

Discussion in 'Lighting and Electrics' started by Jamie, Jun 29, 2007.

  1. Jamie

    Jamie Member

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    so i'm planning for a show in august and had some general questions that i think other could benefit from.

    my first question is in regards to tapping into the venue's power supply. they have a company switch that is a three-phase, 240volt, 200amp. i have access to a number of powerDistros, but i'm not sure if the 240volt will work as I have only seen them used for 120v stuff previously. if the voltage doesn't matter, than life is easy - but i'm not sure

    secondly, we're hanging two 30'truss pieces with two 1/2ton CM hoists on each end. on the PD's i've seen a 60amp motor cable output, and was wondering how the whole motor system works. does power from the PD go to a motorControl that has independent outs for each motor?

    thank you all for your help and I hope others learn so that i'm not the only idiot around here ;-b
     
  2. avkid

    avkid Not a New User Fight Leukemia

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    Are you sure the input voltage is 120V single phase?
     
  3. Footer

    Footer Senior Team Senior Team Premium Member

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    well, I'm first going to say if you don't know how a motor works system works putting one in the air ain't the best way to figure it out. Most motor controllers have their own three phase input (at 208v). A motor controller with have two outputs for each motor, a control line (pickle line) and a power line. You then have a large pickle that hooks up to the controller that has up/down and bump switches for each motor. For a two motor setup I would usually run them strait off of the pickles to set their trim unless I was getting the controller with the package. As far as the voltage for them goes, ask your company you are renting from. There are a variety of different ones out there.
     
  4. stantonsound

    stantonsound Active Member

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    I will tackle a little part of this. If it is truly 240volt, you can not just divide it up to get 120 volt, you must use a transformer. This is not something that you can do for a show.

    Most chain motors use 208volts (or you power the controller with three phase 120volt power). They have 120 volt motors if the half ton variety, but that is the only type that I have seen. I have used these on several occasions and I love using them. I do not need to worry about power at the venue, and it is so easy to power them, provided 1/2 ton is sufficient for your needs.

    Load in is usually a little crazy, no matter how experienced the crew and how many times they have done it. People always get in the way of someone else working. With 120volt chain motors, the people putting the truss us do not need to get in the way of anyone else when it comes to running power. They can power their stuff with a wall outlet if necessary, and make the big shiny stuff go up in the air.
     
  5. Van

    Van CBMod CB Mods Premium Member

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    I will agree with some of what has already been posted. If you are just looking for info, great glad to help you. If you are going to try and rig a motor lifted truss system having never done it or not understanding how it works....... DON"T.

    Ok got that out of the way.

    There may very well be "transformers" out there that are capable of turning 240 three phase into 208, but I've never seen one. The only thing I'm familiar with is a "roto-phaser". Essentially it an electric motor that takes the 240 inputs runs them through a nifty little coil set up mounted to the front of the motor, spins the bejesus out of the coil and shifts the phases of the power to a 208 configuration. If the panel or company switch that is suppling the power is a 240/120 wye then, no, if you don't have a "roto-phaser" you can't run motors off of it. If it's 208/120 three phase no prob. It's a matter of matching the phases to your motor control box and zippity do dah you're in bussiness.

    The Motor cable output of the PD sounds like it might very well be what you would tie into for motor control power. However some distros do have "motor" outputs that are simply for scenic purposes, and are labeled as such since they may have "motor" breaker installed on them < motor breaker isn't the right word but I've been welding and grinding all day and my brain has little metal fillings in it right now.>


    And never worry about being the only idiot around here, As long as I'm here.... you're not alone. :p
     
  6. JD

    JD Well-Known Member

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    I would bet there was a miscommunication about the voltage. If its a company switch, 200 amps, and 120 volts on each leg, three phase, the inter-phase voltage has to be 208. It's simple multiphase math. Give them a buzz and clear that up first. I have to agree with the 120 volt lifts. I used to use half-ton loadstars when we did rigged shows, and the concept of NOT having to wait for the distro to get setup is a huge advantage! Lets face it, until the trussing is off the ground, your pretty much in everybody's way.

    ummm.. Have to echo the above, if you have not rigged a show before don't learn by doing it. The stakes are too high.
     
  7. stantonsound

    stantonsound Active Member

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    Many commercial buildings have 277/480 power running from the main switch gear room to the smaller electrical rooms in the building. It is more efficient to run a higher voltage over the long distances. The 277 is used for the lighting, the 480 is used for the larger motors (if there are any), and then there is a transformer that sits in the corner and steps the 277/480 down to 120/208 for standard receptacle use. This is what I was referring to, I was not sure if they were talking about a 120/208 system or a 277/480 system. i can not really think of any reason that the power at the company switch would be 277/480, but I have seen weirder things!

    As far as the part about not putting truss up if you don't know how to do it, don't, I completely agree. The info provided was strictly about the electrical needs of chain motors. Hiring a rigging company, or hiring riggers to come in is the best thing to do.
     
  8. len

    len Well-Known Member

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    The controller and the motors need to have the same connections. I've seen both types, where the power and control are separate, and where they are one cable. Obviously, the controller and the motors must be compatible. If you're renting, it's a question you should ask. Remember to get a cable that will go to the far end of the truss, then all the way down from your trim height, then another 20' minimum for error, because what you drew up can NEVER account for every factor.
     
  9. Jamie

    Jamie Member

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    i'm interning at a concert production company now this summer, so i'm edging into rigging. i agree that someone shouldn't just wake up one morning and decide to fly truss!
    the rigging guy is off for the next week or so and i needed some answers before then, but i'm going to go back and double check everything with him when the actuall show comes.
    thanks!
     
  10. Sean

    Sean Active Member

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    They do in fact make 1 ton single phase (120v) motors. We have a bunch at work. Yes, it's nice to not have to deal with a PD. They are more sensitive to electrical overloading though. You're more likely to have the contactors chatter, etc, because the draw on the single phase motors is pretty high. I don't recall what the amperage is, but I've heard from dealers and CM a couple times they prefer that ONLY the motor be on that circuit, because of the high draw when you start it running.

    --Sean
     
  11. SHARYNF

    SHARYNF Well-Known Member

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    Be aware that for most distro systems for concerts etc, the company switch should be 208 3 phase, and connected to a y three phase. You can check this by seeing if across two hot legs you get 208 volts. On the other hand some motors are truly 240 volt three phase which is DELTA, here you will have 240 volts from hot to hot and it is very dangerous to attempt to connect a power distro to this system. Reason is that the neutral is a corner neutral and one of the legs to neutral will be what is called a wild leg and will have a much higher than 120 to neutral voltage, so if you connect a standard distro to this setup, one of your distro sections will have dangerous high voltage, and will probably blow out your equipment. In situations where this is the only power available an experienced electrician will in an emergency just use two legs of the system and convert the distro to single phase. This of course is way way out of the realm of the "weekend warrior" type no offense intended/
    IF you are just looking at what is printed in the switch box, this can be confusing, reason is that there are a lot of three breaker switch boxes that can also be used for 240 and 208 three phase for disconnects of motors. So you really need to check the actual voltage vs read what is printed on the switch.
    Sharyn
     
    Last edited: Jun 30, 2007

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