Boost 100-150V ac to 600V ac

Discussion in 'The Projects Forum' started by FrankenPC, Nov 24, 2012.

  1. FrankenPC

    Thread Starter New Member

    Nov 24, 2012
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    Hi, I'm working on a steampunk-ish project. It needs a ~600V AC power supply and I want it to be generated using partial mechanical motion. To that end, I have a H bridge controlled 18V DC motor and a 100-150V AC generator coupled together. Good stuff. Now that I have an alternating power source which I need to boost to about 600V before rectifying it up to around 900V DC.

    So, the alternator only puts out about 24ma. I've tried 6-12V : 110V transformers and the amplification does not work. Either the transformers are not capable of working under the frequency or 24ma isn't enough to generate the EMF necessary to couple the coils. I don't know enough about electronics.

    Where should I go from here? Remembering it needs to be relatively small, should I try to wind my own 4:1 toroid or something along those lines? How would you approach this problem?

    Thanks!
     
  2. wayneh

    Expert

    Sep 9, 2010
    12,154
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    It should work, and 24mA would be plenty. What frequency are you using? Also, are you sure you're getting 24mA with the transformer secondary attached? It will be low impedance and will look like a short to the power supply. Your voltage is probably pulled very low due to that.
     
  3. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    You would be better off winding a 4:1 ratio toriodial transformer, this would give you 600V at 50Hz.
     
  4. FrankenPC

    Thread Starter New Member

    Nov 24, 2012
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    The frequency is MUCH higher than that. It's a drill motor. Somewhere between 600 and 1800 RPM is where it operates best. That correlates to 100-150V AC on the generator side. Does that make a difference to a toroid transformer? At what point does it get saturated and start choking?
     
  5. FrankenPC

    Thread Starter New Member

    Nov 24, 2012
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    Hi, thanks for responding. I didn't think about that. I'll try passing the secondary through a full wave rectifier and measure the DC. The diodes should present a good enough load.
     
  6. wayneh

    Expert

    Sep 9, 2010
    12,154
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    I meant the normal secondary that is now your primary. It's probably too big a load on your "alternator" and pulling your voltage pulses very low. The ideal load - for maximum power output for a given rpm - would have an impedance equal to the impedance of your alternator. You can estimate that by using a series of resistive loads on your alternator and plotting power vs ohms. You'll see a peak at, say, 100Ω. Higher ohms reduces current more than voltage goes up, lower ohms drops voltage more than the current goes up.

    Your wall wart's old secondary has an impedance quite a bit below your alternator's, so you're way back down the power curve.
     
  7. FrankenPC

    Thread Starter New Member

    Nov 24, 2012
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    OK, I'll give that a shot. Thanks for the info.
     
  8. FrankenPC

    Thread Starter New Member

    Nov 24, 2012
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    Can I add a resistor in series with a coil to simulate the impedance match? Or is that counter productive?
     
  9. SgtWookie

    Expert

    Jul 17, 2007
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    The transformer designed to run off of wall power would have far too high inductance to operate with high frequency; it's designed to be efficient at 50Hz to 60Hz.

    You will need a high frequency transformer. A toroid would work. However, it would help a lot if you could give us a frequency range for your generator's AC out.
     
  10. FrankenPC

    Thread Starter New Member

    Nov 24, 2012
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    1-3 Khz for the signal.
     
  11. tkng211

    Well-Known Member

    Jan 4, 2008
    65
    2
    If the final power supply you need is 900VDC, you can use simple voltage multiplier consisting of diodes and capacitors. You may take a look at http://www.blazelabs.com/e-exp15.asp
     
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