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Simple electric generator

  1. Apr 23, 2014 #1

    If you turn the bit in an electric drill will it generate electricity? What would you need to do for it to produce enough electricity to feed back into the grid?
  2. jcsd
  3. Apr 23, 2014 #2


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    Yes, it will generate electricity. A motor and generator are almost identical. In simplest terms:

    For a generator, some type of mechanical energy rotates a magnetic field around a wire inducing a current. Ussually the force of either steam or some pressurized gas, but in your case, turning the drill is the same thing at a way smaller scale.

    For the motor, the current induces a rotating magnetic field that turns the motor.

    If you take a generator and put a current thru it, it essentially acts like a motor.

    If you take a motor and mechanically turn its shaft, it becomes a generator.

    Since a typical drill is 1 HP, if you could turn it fast enough, you would almost have enough power to make another 1 HP drill operate. So, as you can see, it wouldn't make much sense to do it.
    The generator in the power plant is jusssssst slightly bigger than your average drill to say the least.
  4. Apr 23, 2014 #3
    The hand drill was just an example of something that has an interface (the bit) that would allow for external rotation of the internal rotor, thus making it a handy tool for discussing 'reverse' generation. You'd need a few to make your morning toast!

    if you hooked it up (via all the necessary gears etc) to a water wheel, then could it produce enough power to reduce your power bills?

    obviously a hand drill wouldn't be hugely economical at producing energy, so what commercially available product would be better suited for producing 'reverse' generation?
  5. Apr 23, 2014 #4


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    The electric utility in your area can give you more information about how to interface your home power generation with the grid, so that you can supply some of your own electricity needs, and even sell your excess generation capacity back to the power company. There are important regulations for how you connect your own generation facility to the grid, so be sure to get that information. The power company needs to inspect and approve your connection mechanism before you can connect it to the grid.

    Here is a starting point for your reading: http://en.wikipedia.org/wiki/Home_Power_(magazine [Broken])

    It has some useful references and links at the bottom. The most common power generation that folks are connecting to the grid currently is solar cells (like roof-top units), but that's really only economical via government subsidies (at least in the U.S.). If you happen to have a briskly flowing stream, or strong winds, or some other natural source of power on your property, then it may make sense for you to invest in the power conversion mechanims, and invest in the grid-connection mechanisms.
    Last edited by a moderator: May 6, 2017
  6. Apr 24, 2014 #5


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    Connection to the grid ('Feeding In') is a seriously fraught business and the electricity companies have very strict rules about it. In most parts of the world, you would need to use 'type approved' equipment and have it fitted by a 'certificated' installer.
    Nonetheless, speaking in principle, it's possible. However, you need to ensure is that the voltage, frequency and phase of the AC you are producing are matched to the grid - so that you are actually supplying power and not draining it from the grid / blowing up your equipment (a very possible scenario).

    These considerations apply to every generator that is hooked up to the grid and involve a high degree of control. In the case of a power station, this involves adjusting the steam pressure in a turbine and the rate that coal is fed to the boiler. A bit of a nightmare, in the days when that involved a man, with a meter on the wall, a manual steam valve and a shovel!
  7. Apr 25, 2014 #6
    Thanks for the reply,

    Now for a HUGELY moronic question.

    If we were to take the fabled drill and plug it into the living room wall in the normal way, then turn the bit externally, would the electricity generated go back into the grid (via its connection on the living room wall), either reducing consumption, or making the meter 'go backwards'? Or, if it was a cordless drill, would it recharge the battery. (I'm not as stupid as I sound - promise, I just need to get some simple premises in place)
  8. Apr 25, 2014 #7


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    Your electric drill would make a really bad generator.

    It is a series connected machine which has its field coils powered by the armature current.

    If you just rotated the chuck it would generate only a few volts of DC.

    If you put a load on it, like a small lamp, it would generate a larger voltage because the magnetic field from the field coils would be greater.
    But the output would still be DC.

    So, connecting it to the mains as anything except a drill would be a really, really bad idea.
  9. Apr 25, 2014 #8


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    Please reread Berkeman's post seriously and put some serious thought into it. He told you exactly what you need to know - at least as a starting point.

    The short answer though (and again: you need to put serious effort into understanding the long answer) is no, you can't just plug a drill into a wall, spin it manually, and expect your electric meter to run backwards.

    This is a serious issue and you need to put more serious effort into it.
  10. Apr 25, 2014 #9
    Hi russ_waters,

    I'm not actually planning to connect anything to the grid, whether it be an electric drill or any other device, if I WERE planning to do so I wouldn't come to the PF and ask questions about running an electric drill backwards, I would go to relevant website re the subject and I would contact the national grid and ask them for all the information they have.

    This is a physics forum and I'm asking very simple questions in order to find the lowest common denominators in the field of electricity generation, asking these question and reading the answers helps me to understand the basic principles, and I hope also gets others thinking eg, with the correct rectifiers and grid tiers you could connect your waterwheel powered washing machine to the grid or have it keep your toaster going. What other household items could be re-engineered to perform other tasks....?

    It's about thinking and experimenting with thought.
    Last edited by a moderator: Apr 25, 2014
  11. Apr 25, 2014 #10


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    It's a good thing that you are curious and want to learn. Did you follow my link and do some reading about Home Power? I think you will get a lot out of reading through some of the related links.
  12. Apr 25, 2014 #11

    jim hardy

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    Read up on motors, they're not all that complex.

    Here's a tutorial on the basics and a search on "electric motor fundamentals" finds plenty more.

    Now in this one they use the old notation of current as electron flow, so their "left hand rule" will be a "right hand rule" in modern textbooks.

    Point being - speaking generally a motor and generator are the exact same machine,
    so the electrical - mechanical conversion of energy can go either direction.

    I'm doubtful whether your electric drill would return power to the mains because current is likely to be blocked by the variable speed electronics in the trigger.
    Along same thought lines, inserting the battery backwards into a transistor radio will not make it into a transmitter.

    Induction motors that are slightly oversped will return power to the mains. Your ceiling fan is probably capable of that.

    Your thought experiments will become much more productive if you'll learn the basics.

    old jim
  13. Apr 26, 2014 #12
    Thanks for the replies!

    I'm putting a day aside to read the link Jim, thanks for that. (got 4yo twins, so time's a premium)

    I've been constantly frustrated in my thought experiments by coils. Is there a ready reckoner that can tell you the ideal gauge, number of windings, distance from magnet, speed of pass etc. for a given size and power of a permanent magnet. Such that, if got hold of a 50mm radius n50 magnet I could go to the reckoner, look down the list until I got to n50 and it would tell me all of the optimums for generating the strongest and most useful current (I would imagine that, rather than having a different entry for each size and shape of magnet you could have the 'n50' figure be representative of a 1cm by 1cm (same thickness across the board, probably 1cm) magnet at 1cm distance from a metal plate that's attached to a scale that then gives a pull figure - if no such measurement exists then I claim it! the Marodo scale!!!!).

    Also, how does one determine whether the coils should be connected in series or not?

    Thanks guys
  14. Apr 26, 2014 #13
    Sorry, 50mm diameter would be more realistic for a hobbyist.
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