how a generator works?

Discussion in 'Energy & Electricity' started by redpanther, Oct 20, 2008.

  1. redpanther

    redpanther Guest

    Does anyone know how a generator makes electricity?
  2. Jerseyzuks

    Jerseyzuks Well-Known Member


    A magnet spins inside a coil of wire, moving the electrons through the wire, creating electricity.

    Bigger magnet, bigger wire, more coils = more electricity

  3. Jerseyzuks

    Jerseyzuks Well-Known Member

    On a side note, any electric motor will produce power if you spin it
  4. Blister

    Blister Active Member

    Actually, a flux field of different polarizations (north and south) is passed over opposite sides of the same coil at the same time. The magnets are on what's called the rotor and the coils are on what's called the stator. The coils conduct the flux field which is accelerated and produce electricity.

    Bigger wire will make more amperage and smaller will make more voltage. Voltage will make your hair stand up, amperage will kill you.
  5. JeepHammer

    JeepHammer Well-Known Member

    Sure, it's called 'Electromagnetism' or the 'Electromagnetic Link'.

    The basic principal is,
    When you pass a magnetic field over an electrical conductor, you create an electrical current.

    The MOVING magnetic fields excite extra electrons in the outer most orbits on conductive materials, and they start jumping along the conductor either towards, or away from the magnetic field depending on if it's a 'North Pole' field, or a 'South Pole' field on the magnet.

    Reverse the situation,
    And run an electrical charge through a conductor, and you will create a magnetic field...
    ANY MOVING CURRENT will produce a magnetic field around the conductor.

    ANY MOVING MAGNETIC FIELD will produce current in any conductors around it.

    Some simple experiments you can do to test the 'Electromagnetic Link' yourself.

    Take some insulated wire, make several wrap it several times around a bolt or spike nail, and add a battery to the ends,
    The bolt or nail or what ever you used to focus the magnetic field will pick up nails, since with the current 'ON' it will be magnetic!

    Here is a link to moving a magnetic field through a coil of wire.
    Molecular Expressions: Electricity and Magnetism - Interactive Java Tutorials: Faraday's Magnetic Field Induction Experiment
    You can do this one your self by shaking any of the 'Emergency' flashlights they make with the big magnet and coil of wire inside, then simply turning it on.

    Here is one I like, this shows you can make an electro magnet with a battery and once coil of wire,
    And transfer the power to the coil of wire on the other side of a Ferrous (metal) ring.
    Molecular Expressions: Electricity and Magnetism - Interactive Java Tutorials: Faraday's Experiment

    Now, if you want to the long winded version, try here,
    Faraday's law of induction - Wikipedia, the free encyclopedia

    Modern generators, the small scale versions, use PERMANENT MAGNETS and coils of wire to produce electrical current.

    Other, larger generators, like car 'Alternating Generators', or 'Alternators' use an electro magnet to produce the magnetic field.

    Here is a pretty good resource for working with small alternators... Secrets.htm
    And in this case, it's free.
    Last edited: Oct 20, 2008
  6. solaceofwinter

    solaceofwinter Guest

    kind of a dumb question but...
    aside from how they actually generate electricity, how do they 'work'.
    i mean how do you get electricity from it into your home or appliance? do you just plug the lamp 'into it?' thats what i never understood.
    and if you just plug items into it how would you run your house on it? could you?
    you always see the scenario, power goes out, 2 seconds later powers back on in the whole house.
    is this how they work or a bit of a stretch? thanks!
    Last edited: Oct 29, 2008
  7. northernontario

    northernontario Well-Known Member

    Ok... your average small generator has a panel on it with a couple of 110v plugs. If you need power, you head over to your generator, start it up. Now plug in your lamp (or radio, or fridge), turn the item on (if it has a switch... like a lamp, or a radio). Bingo, that's it.

    The generator will have a limit on how much power it can supply (watts). Small generators may not be able to power your fridge or freezer; it depends on the wattage rating of the generator, and how much power the item draws.

    Some mid-sized generators have 220v outlets, and some have 12v outputs to charge batteries as well.

    Now a larger generator is often built into a complete "system" in the house... something you'd get an electrician to install for you if you don't have the skills. An extra panel is added, and the generator is hardwired into the house. A control system is installed which basically sits there and waits for a power outage... your generator has an electric starter and a car battery... when the power goes out, the control unit tells the generator to turn on, and a couple seconds later, power is being fed back into your house.

    You can also do the above setup, but without the controller... so if the power goes out, you have to manually start the generator. This gives you a chance to shut down power-hungry appliances (like a heat-pump if your house has one), start the generator, and turn on individual appliances as they require power. (If your generator isn't powerful enough to run both your fridge and freezer, you would kill the breaker to one of them or unplug one, run the other for an hour or two, then switch to the other appliance to cool it down.)

    That give a good enough explanation, or is there a more specific scenario you'd like described?
  8. solaceofwinter

    solaceofwinter Guest

    you got it brother, thanks!
    pretty interesting stuff. the power rarely goes out here and its just outside city limits but you never know...
    thanks again!
  9. labotomi

    labotomi Well-Known Member

    No, it would have to be a permanent magnet motor and most motors are squirrel cage induction. This means they create their own magnetic fields and don't rely on a magnet.
  10. labotomi

    labotomi Well-Known Member

    I have no idea where you got that, but voltage is what is generated and the amount of voltage is proportional to the strength of the magnetic field, number of conductors and relative speed of the conductors and magnetic field.

    Bigger wire will carry more current without burning up. Wire size has no affect on voltage in the way you're implying. If anything, smaller wire will result in lower voltage due to voltage drop caused by the resistance of the wire.
  11. Tex

    Tex Pincushion

    Maybe Blister meant that larger coils with more windings will creat a larger voltage.
  12. labotomi

    labotomi Well-Known Member

    that would be true
  13. JeepHammer

    JeepHammer Well-Known Member

    Actually, smaller wire in the windings will produce more voltage,
    While large wire in the same space will produce more amperage at lower voltages.

    Multiply your voltage times amperage to get 'Watts'.
    Volts X Amps = Watts.
    This gives you a way to equalize the output of high voltage/low amperage vs. high Amperage/low voltage generators.

    12 volts X 10 Amps = 120 Watts
    120 volts X 1 Amp = 120 Watts

    Or with a gasoline generator rated in 'Watts', it will usually have 120 volt outlets and a 220 volt outlet, but the amperage available won't be the same...

    4,000 Watts ÷ 120 Volts = 33.33 Amps
    4,000 Watts ÷ 220 Volts = 18.18 Amps

    The higher the amperage you want to use, like for running a welder instead of a light bulb or two...
    You will have to know what the amperage load you are pulling through the conductors...
    Lights will work just fine in 16 Ga. wire,
    Where a 30 Amp welder needs at least a 10 Gauge wire conductor.

    With smaller wire, there is more conductors to 'Induce' voltage in, but the smaller wire restricts Amperage.

    With larger wire in the same space, you can't have as many windings,
    But the larger wire size will support more Amperage.

    When I'm rewinding a car alternator for wind or hydro production,
    I have to balance between voltage output, and usable amperage.

    Since most generators you will be messing with produce in AC or Alternating Current, and WILL NOT produce a directly usable current for something like lighting,
    You will have to find a way to 'Filter' that power into a usable form.

    The easiest way is to use a 'Rectifier' that converts AC to DC (Direct Current).
    Direct Current is VERY usable, and it's what batteries put out.

    Then your DC current can be converted via an 'Inverter' into AC with the correct 'Cycles' for you AC appliances.

    Most people that produce AC from a home generator (gas, wind, hydro) will either charge a battery bank,
    Then draw from the battery bank through an Inverter for their AC power,
    Or use the DC directly from the batteries.

    They will use appliance intended for DC current,
    Like the stuff made for traveling in cars that plug into the cigarette lighters.

    Batteries give you the option of making very little generation over long periods of time (hours) that adds up,
    Is stored in the batteries,
    And then can be used at high current loads for short periods of time,
    Like when you have a 12 Volt, 5 Amp wind generator that charges batteries,
    Then you run a large load for a short period of time,
    Like a microwave oven to make dinner.
    Last edited: Mar 28, 2010
  14. labotomi

    labotomi Well-Known Member

    If you re read my post, you'll see that I said the same thing as you in the latter part of your post.
    I was just stating that the size of the conductors isn't the controlling factor for's the number of conductors. I will agree that wire size can limit the current you can safely carry.
    Why is AC not usable to power lighting? Every light in my house is powered by AC.

    Gas powered generators can produce enough energy to power AC appliances directly without the need for batteries and inverters which would lead to lower efficiency as some power is lost with every conversion. Also adding batteries and inverters where they aren't needed is a waste of money.

    Wind and hydro I can see it as the generators are too small to produce immediate power, so accumulating it over time makes sense.
    Solar generates DC so Batteries and inverters are a necessity.
  15. JeepHammer

    JeepHammer Well-Known Member

    Small, Home made generators have a tendency to be made from electric motors or car alternators.
    They have a tendency to have 'Cycle' counts that cause 'Flickering' or detectable 'Blinking' of the lights we have now.

    Wrong cycle counts can burn up all sorts of electronic devices, but are especially hard on motors wound specifically for a specific cycle count,
    And on transformers that like to overheat when subjected to higher cycle counts...

    A capacitor will stop or at least minimize that flutter, but you will still see it,
    And with electric motors, you will find that that many of them aren't compatible with the 'Cycles' of the generator.
    They will do strange stuff, or just burn up when you try to run them directly off a home made generator.

    Grid energy is a very constant 60 cycles a second,
    Where your generator might be 400 cycles a second, or 10 cycles a second.
    (Cycle is where current flips form positive to negative and back again,
    AC does this 60 times a second from the grid,
    Where DC power doesn't do it at all)

    If the motor is built correctly, you can run it on about any type of current,
    Amount of current will determine speed.
    Low current = Low speed...

    If the motor is build specifically for AC current, it will melt down when you try to run it on DC current.

    Same if it's the other way around,
    You have a DC motor and try to run it on AC current.

    Some motors are wound for specific input cycles,
    Can't run them on anything else correctly...

    For instance, your cordless drill works great on DC current,
    But if you plug it into an AC outlet, no matter if the voltage is dropped down to 18 volts or whatever,
    It's going to burn that DC motor up in short order!

    Generator has to match equipment to run directly off the generator...
    That's why batteries and converters/inverters that put out SPECIFIC current type are very handy to have...
    Last edited: Mar 28, 2010
  16. labotomi

    labotomi Well-Known Member

    Please don't think you have to "simplify" your wording for me. I spent 10 years as a Nuclear trained electrician on Navy submarines before getting out and spending another 10 as an electrical engineer (by title, not degree) at a large manufacturing facility. I'm familiar with how electricity works so you don't have to dumb things down for me to know what you're talking about.

    Generally what you're saying is correct, but their is much misinformation there as well. I'm not going to point out the errors in your post as this isn't a me against you thread. Just try and stick to the original question asked by the OP.

    Does anyone know how a generator makes electricity?

    I was just commenting on basic generator theory (which was hammered into us by the Navy), not application specific home/small alternator/off the grid stuff.

    Ok. I can't resist.

    you can only run one type of motor on AC or DC. It's called a universal motor and I can think of only two applications currently being used in residential settings, drill motors (corded) and shop vacs (maybe all canister vacs. I dunno)

    DC Motor speed is controlled by VOLTAGE.

    AC Motor speed is controlled by APPLIED FREQUENCY (60hz)

    Yes, running a AC motor at SLOWER frequencies can make them overheat (Inductive reactance goes down causing current to increase)

    incandescent lights would have to have a very low frequency to flicker since they give off light due to their heat and it takes some time for the cooling to occur. Look at a light when you turn it off and watch it fade. Even at as slow as 10Hz, I believe any dimming would be undetectable by the human eye.

    Fluorescent lighting does actually turn completely on and off at 2X applied frequency. in your home that would mean 120x/second. They can also be run off of DC but it will significantly reduce the life of the bulbs. This probably would be noticed by a very low frequency, but that's why adjacent florescent lights are wired to opposing 120v circuits. This makes the flickering alternate in adjacent pairs. This was done to prevent similar effects as a stroboscope on rotating equipment which would cause anything running at a harmonic frequency of 60 Hz to appear as if it were rotating very slowly or not at all.

    A capacitor will help with dips or spikes in DC voltage, but would be counterproductive in an AC circuit because capacitive reactance is inversely proportional to frequency meaning the lower the frequency (or cycles as you put it) the more the capacitor tries to stop current flow. (1/(2*pi*freq*capacitance))

    Last edited: Mar 28, 2010
  17. JeepHammer

    JeepHammer Well-Known Member

    What ever you say...

    I'll go back to my job of wiring 'Green' energy stuff.
    Last edited: Mar 29, 2010
  18. model130

    model130 Active Member

    Quick amperage test of appliance.

    Make a plug and electrical extension cord of heavy wire. Or buy a short one.
    Cut off the main insulation leaving the 3 wires (with insulation on) exposed. Plug your appliance into the cord and the cord into the wall. Put a clamp on amp meter over the hot wire and read the amperage. Convert that to wattage and you will know how much current each of you appliances uses and how far you can stress your generator. You might find this interesting. We had a cable box pulling as much amperage as our refrig!
  19. labotomi

    labotomi Well-Known Member

    For less than $20 you can purchase one of the "kill-a-watt" meters. They plug into the outlet and you plug the appliance into it. It will give you the following measurements

    Voltage (volts)
    Current (amperes)
    Kilowatt-hours (kW·h)
    Frequency (Hz)
    Volt-amperes (V·A)
    Power factor (PF)
    Elapsed time
  20. nj_m715


    Awhile back I posted a link to how I made welder/genset with an alternator and lawnmower engine. I can charge 12v batteries or bypass the regulator and make about 70 volts DC. It will light up a standard light bulb and run most power tools. Any AC motor with brushes can run on DC once the volts are high enough. It doesn't have to be 110v. You can do the old jumper cable trick with a couple car batteries to increase the volts too. I modified my truck alternator too. It can make about 100v before the engine is turning too fast. Of course I don't rebuild nuke engines, but I know just about enough to get myself in trouble.

    "If the motor is build specifically for AC current, it will melt down when you try to run it on DC current."