Some basic generator/motor questions

Discussion in 'Physics & Math' started by thall53, Feb 9, 2011.

  1. thall53 Registered Senior Member

    Messages:
    65
    I've recently become interested in building a generator to produce electricity. I am very new to this and would like to get some background information before purchasing materials. I've looked online everywhere I can think and cannot find the answers to these basic questions:

    How does wire thickness and number of times the wire is wrapped affect electricity production in a generator?

    Essentially, how can I optimize electric production? More wrappings of a thin wire or fewer of a heavier one?

    Also if anyone can suggest some quality reference materials I would appreciate that as well.

    Thank you in advance for you help!
     
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  3. Read-Only Valued Senior Member

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    10,296
    Unless you want to do this for just a small demonstration model, you'll discover that making a practical generator involves far more than you've bargained for.

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    You'll have to build both a rotor and a stator and if it's a generator, you'll also have to construct a commutator, brushes and brush holders. If it's an alternator, you'll need slip rings instead of a commutator (and still provide brushes and their holders). And since you'll find that permanent magnets don't produce a strong enough field, you'll have to provide excitation current to field windings - and that also requires an electronic control to maintain the output voltage at a stable level because it will vary with the load.

    It's much more than just a matter of winding wire and connecting it to something (called a prime mover) to run it.

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  5. origin Heading towards oblivion Valued Senior Member

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    You would definitely want to buy a generator or a motor for this. A generator is usual more expensive than a motor and it is more efficient at generating power than a motor. The thing is that you can usually buy a used DC motor for a reasonable price. Just make sure it is a LOW rpm motor with a high current requirement.

    Just for clarification if you apply power to the motor it will turn the shaft. If you turn the shaft the 'motor' will become a generator.
     
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  7. Fraggle Rocker Staff Member

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    Do you mean one that can actually power an appliance, or maybe your entire house, in an emergency?

    You'll have to start out small and build a tiny one first, one whose only purpose is "proof of concept." This will show you whether or not you know what you're doing, and can do the work precisely enough for the artifact you're building to be safe.

    What are you going to use for fuel?

    You have to be careful that it doesn't overheat and start a fire, that it doesn't make sparks and cause an explosion, that it doesn't leak fuel, that it's stable and not easy to knock over. You also have to get just the right voltage out of it if you plan on using it to power your appliances.

    Depending on where you live, the power in your house could be AC, alternating current, in which case you need to build an alternator, or DC, direct current, in which case you need to build a generator. (Household emergency "generators" in the USA produce AC, but that's imprecise nomenclature.)
     
  8. cosmictraveler Be kind to yourself always. Valued Senior Member

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    33,264
    An electromagnet is a type of magnet whose magnetic field is produced by the flow of electric current. The magnetic field disappears when the current ceases. Electromagnets are very widely used as components of other electrical devices, such as motors, generators, relays, loudspeakers, hard disks, MRI machines, scientific instruments, and magnetic separation equipment, as well as being employed as industrial lifting electromagnets for picking up and moving heavy iron objects like scrap iron.

    An electric current flowing in a wire creates a magnetic field around the wire (see drawing below). To concentrate the magnetic field of a wire, in an electromagnet the wire is wound into a coil, with many turns of wire lying side by side. The magnetic field of all the turns of wire passes through the center of the coil, creating a strong magnetic field there. A coil forming the shape of a straight tube (a helix) is called a solenoid; a solenoid that is bent into a donut shape so that the ends meet is called a toroid. Much stronger magnetic fields can be produced if a "core" of ferromagnetic material, such as soft iron, is placed inside the coil. The ferromagnetic core magnifies the magnetic field to thousands of times the strength of the field of the coil alone, due to the high magnetic permeability μ of the ferromagnetic material. This is called a ferromagnetic-core or iron-core electromagnet.

    The direction of the magnetic field through a coil of wire can be found from a form of the right-hand rule.[1][2][3][4][5][6] If the fingers of the right hand are curled around the coil in the direction of current flow (conventional current, flow of positive charge) through the windings, the thumb points in the direction of the field inside the coil. The side of the magnet that the field lines emerge from is defined to be the north pole.

    The main advantage of an electromagnet over a permanent magnet is that the magnetic field can be rapidly manipulated over a wide range by controlling the amount of electric current. However, a continuous supply of electrical energy is required to maintain the field.

    http://en.wikipedia.org/wiki/Electromagnet
     
  9. Thoreau Valued Senior Member

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    Everyone here has contributed some pretty knowledgable answers and sources. And I'm here to do just that. I work in the Power Generation industry and am a certified technician and have been for 8 years now. If there is something I can assist you with, feel free to PM me. Thank you.
     
  10. Dr_Zinj Registered Senior Member

    Messages:
    38
    You CAN build a primitive generator out of insulated copper wiring, a few nails, a block of wood, couple of flat kitchen fridge magnets, glue and a piece of cardboard. I did as a Boy Scout Electricity merit badge project way back in the dark ages of the 1970s. (The cardboard was for a fan blade as wind power was the prime mover. Enough to light a grain bulb.)

    Didn't take a whole lot of windings and the whole apparatus was about the size of two fists.
     
  11. quadraphonics Bloodthirsty Barbarian Valued Senior Member

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    No, it isn't. A generator is any device that converts mechanical energy into electrical energy - doesn't matter whether the output is AC or DC. The term "alternator" refers to the specific case of AC output, and the term for a DC generator is "dynamo." However, nobody uses that latter term any more because nobody uses generators to directly produce DC output any more (except in museums, or for demonstration purposes) since the rise of solid-state electronic AC-DC converters. I.e., even if you want a DC output at the end, the way to go is to build an alternator and then hook it up to suitable electronics to get the DC output. So, the term "generator" has come to imply AC generation, since that's effectively the only kind that anyone actually does.
     
  12. quadraphonics Bloodthirsty Barbarian Valued Senior Member

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    9,391
    Why?

    I.e., is this for an actual practical purpose, or for fun/hobby/science fair or something? If it's the former, you're almost certainly better off just buying a generator.
     
  13. ULTRA Realistically Surreal Registered Senior Member

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    1,555
    In England, the frequency of the power is 50hz. If you didn't increase the power, but introduced a far faster switching capability - say 500,000hz would you produce more power, because as I understand it, the power comes from magnetic lines of force intersecting the copper coil. If this was stepped up would it not produce more power?
     
  14. Pete It's not rocket surgery Registered Senior Member

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    10,167
    If you don't increase the power, then you don't increase the power, right?
     
  15. Read-Only Valued Senior Member

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    10,296
    The frequency has no direct bearing on the amount of output power. The power out is simply a result of the mechanical power input times the efficiency of the system. 1 Kw at 50 or 60 cycles is the same as 1 Kw at 500,000 cycles.
     
  16. ULTRA Realistically Surreal Registered Senior Member

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    1,555
    Ok. Got it. Yeah, makes sense.
     

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