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Power newbie

Discussion in 'Lighting and Electrics' started by emanueltech, Oct 7, 2004.

  1. emanueltech

    emanueltech Member

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    Location:
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    Dear Friends,
    I am a sound techie, but often have to step in during rehersals to cover for my light techie, due to this i can tech a show on a master piece, etc express and tempus 24. I can also rig lights patch etc. but up till now i havent done the lighting plans and i know nothing about power really. I really want to learn about power so i can do my own rig plans. Im living in england. I need to link voltage current power, to be able to work out if i am going to overload the system
    and also i have been employed to rig some small garden parties (probably using 3 x 6 channel dimmers) so i need to be able to work this out to discover where i need to get power from. Please help all advice greatly appreciated :eek:

    TC
    essd
     
  2. JahJahwarrior

    JahJahwarrior Active Member

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    I'm no genius either, hopefully Ship or someone will post here, because there are people here that know ALOT more about this than I do, but I want to chip in because then they can tell me what I do wrong :)

    Basically, there are several factors about electricity, voltage, amperage and wattage. I cannot explain them very wel, but voltage is how much energy is in each atom. Are you on 240? Amperage is how many atoms there are, and wattage is how much energy something pulls. (again, don't trust me on this, make sure that Ship or someone clarifies, I might have those wrong) they are all related by forumalas, but I do not know them. Like, if you know two things, ou can use a formula to figure out the third.

    All things use power, and you can see how much by their amperage and wattage. Standard circuits in the US are 15 amps, with special plugs for 20 amp, at 120 volt. Say youo have a power saw that takes 15 amps, then you hev to have a 15 amp outlet (which is what most outlest are) and a 15 amp cable. If your extension cable is only ablve to carry 13 amps (ther ewill be a rating on the box of extension cords) then you shouldn't use it, it won't give enough power to your saw. I have no idea how many amps dimmer packs draw, it ought to be on there somewhere. Wattage is another thing that electrical things use. Most lamps here in the US are 300, 500, 575, or 1000 watts. On a dimmer pacck they will say how many watts each channel can handle, and how many the dimmer pack can handle total. If you have a 1200 watter per channel 2400 watt total dimmer pack, then you can only have two channels fully loaded on at the same time. If you turn on a third channel when the first two both have 1200 watts on them, and so does the third, then you will blow a fuse or a breaker. All your lamps will have a wattage on them. So, first youo need to make sure thep lacec youo are going to has the power hookup you need, the right voltage and amperage. Then, you need to calculate how many lights you are going to have, their wattage, and all that, to figure out how many ilghts per channel, and how many will need to be on at the same time. For instance, in the pre-mentioned dimmer with 1.2k channel, 2.4k total, wattage, you could have each channel loaded to 1200 watts (by using two 575 watt lamps) but, you can only have two channels on at the same time. Other dimmer packs will let you have all channels on at the same time, say, a 4 channel pack, 1.2k/channel, 4.8/total dimmer pack,you could have all channels loaded to 1.2k watts, and all of them on at the same time.

    Anyways, I have to go eat dinner, hopefully someone else can add to this!
     
  3. propmonkey

    propmonkey Well-Known Member

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    Location:
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    im taking an electronics class right now. think of
    elctricty as water. lets say you have 20 gallons(which is like voltage). how fast the water/electricty moves is the amps. so you could have 1000V co through you and not be hurt as long as the amps are low, it takes just one to kill you.

    http://www.elec-toolbox.com/Formulas/Useful/formulas.htm

    http://science.howstuffworks.com/question501.htm <---- that explains it the best

    http://www.singaporetheatre.com/technical_theatre/theatre_safety/theatresafety.htm
     
  4. bdesmond

    bdesmond Active Member

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    Location:
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    Well, here's the first thing you should learn about electricity: It kills the first time. Don't be messing around with any quantity you don't know how to deal with. Given the nature of your question, I think a good line for you at this jucnture in terms of power you should be dealing with is the batteris you can pick up at the local store. I don't mean to be harsh, but, it's signficantly more difficult to do something life threatening with some AA batteries than if you've got your fingers in a 1900 box.

    THat said, plugging in fixtures is probably not life threatening assuming the wiring and fixtures are in good operating condition.

    So, to answer your questions:

    There are three units in particular we need to worry about here:

    Watts (W)
    Volts (V)
    Amps (I)

    Watts is the rate at which power is being used. If you go look at your electircal meter on your house, you'll see the unit on there is kilowatt hours (kWh)

    Voltage is the different in eletrical potential between two points. Think of it as when water is flowing - water flows downhill. Likewise, electricity flows to the point of highest potential. The positively charged terminal on a battery, for example.

    Finally, amperage is the rate at which the current is flowing. The number on a circuit breaker or the front of a dimmer is usually the amperage the breaker is rated for before it trips off. Wire comes in different gauges, and each gauge has a maximum current rating. Running 30 amps through some 18 gague would be a good wya to start a fire. So, instead you throw a 10 or 15 amp breaker in front of the run - prevetns this from happening.

    The usual water analogy implies to these three units - watts is the number of gallons of water you're using, voltage is the water, and amperage is the speed the water is flowing.

    All three of these units are related mathematically. If you need to find amps (I), you divide watts by volts. Likewise, total wattage is volts times amps, and, voltage is watts divided by amps.

    So, if you have a 1000W lamp running at 120V, you'll need eight and a third amps of power.

    In the US, breakres don't blwo hardfast at the number printed on them. I know in Europe, this isn't the case - I have no idea what the drill is in the UK. Someone hear may know.

    Always consult an electrician in your area if you're not sure what to do, or if what you're doing is safe or allowed. They're going to be the people that know the rules in your area, and are most able to train you. Explaining these sorts of things over the Internet is not very easy to do, and is dangerous given that there isn't osmeone watching over your shoulder.

    Hope this helps.
     
    chausman and (deleted member) like this.
  5. rgsw

    rgsw Member

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    get your hands on some zero 88 betapack plus's. we are kitting our school out with them because they double up as patch bays. the great thing about the betapack plus it that they have local control on the front of them so you dont' have to have a lighting board for a small event.

    we are running them off an 100A three phase supply as each unit draws 63A (i think). this will create problems when running off a 13A socket but this is obvious as most lanterns pull about 5A anyway
    http://www.zero88.com/products_main.php?prodID=12

    don't hesitate to pm if you want to know any more bout betapacks or electrics in the uk as us british people seem to be one of a kind on this forum :D
     
  6. emanueltech

    emanueltech Member

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    Location:
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    so would this be correct : an example please say if its worng

    MY QUESTION
    I have a 13 amp (230v) plug socket. I plug in a 13 - 15 amp adaptor. How many 500 watt lamps could i use if i linked them all to this plug?

    ANSWER
    v = watts/amps
    = 500/13 = 38.46
    230/39 = 5.8

    so you could run 5 x 500 watt lamps

    IS THIS CORRECT
     
  7. rgsw

    rgsw Member

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    yes

    Each 500W unit uses 2.17A (based on 230V, UK average +-10%)

    (500W/230V=2.17A)

    So you should be able to run 5 with a bit to spare and you may be lucky enough to get a sixth :!:

    I would recommend against this as the fuse may keep tripping if you flash the lights. If you bring up the 6th light very slowly you could get away with it as you can technically run 5.99 500W lamps as :

    13A/2.17A=5.99
     

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