Can anyone please help me

Discussion in 'The Projects Forum' started by Profiteer, Sep 28, 2011.

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  1. Profiteer

    Thread Starter New Member

    Sep 28, 2011
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    I am working on a project that requires that I automatically reverse polarity on a High Voltage (1200 VDC) electromagnet at I believe 60 times a minute in order to achieve 60htz which is the American power standard if I'm not mistaken. But I can find nothing online to help me.
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    Well, how much experience do you have working with high voltage?

    You ARE aware that you could be killed instantly by that kind of power, right?
     
  3. SgtWookie

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    60Hz (60 cycles per second) is indeed the frequency of the power grid in the USA.

    In the other thread you started about this, you mentioned 3600 for some reason. That would be cycles per minute. Perhaps you're getting RPM and Hz confused?
     
  4. Profiteer

    Thread Starter New Member

    Sep 28, 2011
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    I am a 12 year veteran industrial electrician and fully aware of the dangers and the precautions to take that it not the issue I just wanted to know if there was a circuit I could build to automatically reverse polarity of the electromagnet at the right time intervals to get 60htz usable electricity.:)

    PS: Sorry about the double post My computer crashed and I didn't realize that the other post even went through
     
  5. SgtWookie

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    OK, I see. Have to ask, you know - 1.2kv DC if stored in a cap bank is a LOT of potential energy.

    What kind of power were you planning on getting out of this project? Standard residential 60Hz 240VAC split phase, 120v/phase? Or are you just trying for a square wave output?

    What's the nature of your load? If it's purely resistive (such as incandescent lighting) you wouldn't have to get very fancy about it; a square wave or pseudo-square wave would do. However, if the load is reactive (appliances, computers, motors, etc) you really would need a regulated sine wave output, and that would be a fairly advanced project.

    You can find what looks like "simple" inverter schematics on the Internet consisting of a re-wound microwave transformer, a couple of transistors, a couple of caps and some resistors - and they either just don't work, or work very poorly.

    If you're wanting something that puts out a pretty good facsimile of a sine wave and is regulated, the circuit is going to be pretty complex.
     
  6. Profiteer

    Thread Starter New Member

    Sep 28, 2011
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    The project is a generator to supply power for my entire house and my shop I need usable 120 volt 60hz power from the generator. That is why I need to switch the polarity of the electromagnet at the right intervals to get the 60hz usable poer from the generator coil.

    PS: I understand why you had to ask and I am not at all offended actually just the contrary there are far to many backyard inventors online throwing out useless and dangerous information to anyone that asks and that is what gets people seriously hurt.
     
    Last edited: Sep 28, 2011
  7. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    What is your primary energy source?
     
  8. SgtWookie

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    Jul 17, 2007
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    Well, that's going to be a pretty ambitious project. A typical modern residential service panel is 200A split phase 240v, so that's 48kW, plus 20% overcapacity is 60kW. If the inverter is 85% efficient, you'll need ~70.5kW input power. :eek:

    Where are you getting the 1,200VDC ~70.5kW power from?

    And what's this "electromagnet" that you are considering using?

    [eta]
    Here's a generator sizing guide published by Generac; just some basic information about sizing power generators for various applications: http://www.mygenerac.com/PublicPDFs/0172610SBY.pdf

    It's not exhaustive, but gives one something to work with when attempting to size a generator or power inverter for an application.
     
  9. Profiteer

    Thread Starter New Member

    Sep 28, 2011
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    There is no inverter the feed is coming off the generator coil putting out 120 VAC at 60hz the whole unit measures 9" x 16" x 6" and is powered from a 12V lead acid battery that is feed through a capacitor/diode voltage multiplier circuit to the electromagnet. One for the house and two for the shop (1@120V, 1@480V). The back emf of the electromagnet is captured and feed back to a second battery that has been depleted to recharge it and the unit is self powered from then on for as long the batteries continue to take a charge.
     
    Last edited: Sep 28, 2011
  10. Papabravo

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    Feb 24, 2006
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    There is not enough power in the battery to do what you want to do, at least not for very long. A typical automotive battery might supply 600 A for a minute at 12V or 7.2 kW which is about 1/10th of the 70 kW you need.

    Voltage multiplier circuits such as those used in automotive paint applications are designd for very low current on the order of 50 microamps. What you want to do is a fantasy.

    AWG 0000 is about two thirds of the diameter you would need to draw 600 amps out of the battery. I'm guessing you need wire with a diameter of 650 mils to carry that much current.
     
    Last edited: Sep 28, 2011
  11. Profiteer

    Thread Starter New Member

    Sep 28, 2011
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    The electromagnet only uses 276 milliamps from the battery so the battery will last a LONG time there is nothing else it has to do but power the electromagnet. I don't mean to be rude but could I please just get an answer to my question can I automatically switch the polarity of the electromagnet at the proper speed to get 120V 60hz power from the coil?
     
  12. Papabravo

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    Feb 24, 2006
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    OK the simple answer is no. Your power in must exceed your power out and your numbers, not to put too fine a point on it, are pure fantasy. That's the difference between an electrician and an engineer. Engineers don't deal in fantasy they deal in reality.
    Code ( (Unknown Language)):
    1.  
    2. 12 V * 276 mA = 3.3 Watts
    3. 3.3W /1200V = 2.76 mA
    4.  
    Are you starting to get the picture?
     
    Last edited: Sep 28, 2011
  13. Profiteer

    Thread Starter New Member

    Sep 28, 2011
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    The battery only feeds the electromagnet which only draws 276 miliamps so the battery will last indefinitely. I don't mean to be rude but could please just get an answer to my question..... how can I automatically switch the polarity of the electromagnet at the right speed to get 60hz electricity from the coil?
     
  14. Papabravo

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    Feb 24, 2006
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    No. There is no switching circuit that will generate 60 Hz AC from a single coil.

    Even if there was a way to do it, you could not even make a CF light bulb turn on with only 2.8 watts = 3.3 * 85% efficiency so what's the point?
     
    Last edited: Sep 28, 2011
  15. Profiteer

    Thread Starter New Member

    Sep 28, 2011
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    is there a circuit that I can use to automatically switch the polarity of the electromagnet? I will worry about getting it to go at the rate that will give me 60hz latter on even if that means I have to add more than one electromagnet.
     
  16. Papabravo

    Expert

    Feb 24, 2006
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    The rate is not even the issue. The issue is generating an AC waveform. What you get from a switching circuit that reverses the polarity is a square wave and not an AC wave form. What you get is a device that consumes power and produces no useful output.
     
  17. Profiteer

    Thread Starter New Member

    Sep 28, 2011
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    what is difference between switching polarity and spinning a magnet over a coil of wire to create electricity?
     
  18. SgtWookie

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    If you want to switch polarity 120 times per second, you will need an H-bridge and appropriate clocking circuitry.

    However, at this point I don't know if you're thinking of trying to switch the power at the battery (dealing with 12v), or at this high voltage thing you've come up with - it's supposed to be 1,200 volts, right?

    And how are you planning on getting power out of this electromagnet?

    You really need a transformer. But, if you're going to be switching at 60Hz (120 reversals per second), you'll need a really large and heavy transformer.

    I have no clue how you think you are going to power your house and garage with 276mA current from a battery, AND charge a depleted battery as well.
     
  19. SgtWookie

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    When you're simply switching the polarity, all of the power comes from electricity.

    If you're spinning an electromagnet near a winding, then you have electrical power being multiplied by the mechanical force applied to spin the magnet.
     
  20. Profiteer

    Thread Starter New Member

    Sep 28, 2011
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    The power is coming from the generator coil, the electromagnet is simply providing a magnetic field to the generator coil to induce voltage in the coil. I need to switch the 1200 VDC that feeds the electromagnet to simulate the spinning of the magnets
     
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