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Thread: operating frequency

  1. #11
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    i could just eliminate the input rectifier. and run 120 dc to that. i have a 120v dc motor i could just belt to the engine. thast would probably be too dirty. wait. u meen after rectifacation, the voltage from the rectifier is 300v!?!? that would n't be much of a prob tho, just finding the right transformer

  2. #12
    FLAC DodgeCummins's Avatar
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    I am not the smartest guy in the group, but if you have a US system that is designed to run off 120vac mains, then when you rectify that (diode bridge) to DC...you get 120vdc (minus a bit for heat transfer)...The European guys can play with the 250v.

    I don't have any idea what a 120vdc motor could be used for, but if you had one, and put a load on it, (with a little rewiring)it would make a dc generator...but it would really be crappy at the job...

    Just get one of those DC-DC power supplies.

  3. #13
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    i have a 120v dc motor i could just belt to the engine.

    Yes, that can work...but aint we going back to the inefficiency situation again?

  4. #14
    Raw Wave Rob Withey's Avatar
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    Quote Originally Posted by DodgeCummins
    I am not the smartest guy in the group, but if you have a US system that is designed to run off 120vac mains, then when you rectify that (diode bridge) to DC...you get 120vdc (minus a bit for heat transfer)...The European guys can play with the 250v.
    Nope, 1.41 times for a full wave bridge rectifier (less a little bit for voltage drop across the doides - the heat transfer you talk of). Don't forget the 120vac is an RMS reading, it peaks higher than that. Same for 250vac.

    See here for more info about bridge rectifiers:

    http://www.mitedu.freeserve.co.uk/Design/dcpsu.htm

    So 250v ac turns into around 350v dc, and 120v ac turns into nearly 170v dc.


    Rob
    Old Systems retired due to new car
    New system at design/prototype stage on BeagleBoard.

  5. #15
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    so it should manage at 120 dc

  6. #16
    FLAC DodgeCummins's Avatar
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    Quote Originally Posted by Rob Withey
    Nope, 1.41 times for a full wave bridge rectifier (less a little bit for voltage drop across the doides - the heat transfer you talk of). Don't forget the 120vac is an RMS reading, it peaks higher than that. Same for 250vac.

    See here for more info about bridge rectifiers:

    http://www.mitedu.freeserve.co.uk/Design/dcpsu.htm

    So 250v ac turns into around 350v dc, and 120v ac turns into nearly 170v dc.


    Rob

    Yes, the resistance across the diodes causing the heat transfer, and the voltage drop.

  7. #17
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    Ok but how you gonna keep the power to your pc if you stall the engine? Its not gonna be easy working with high voltages

  8. #18
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    well, if my engine stals, i got bigger problems than no music! i doubt my engine will stall and i probably won't use the 120vdc generator, ill use a transformer running on pulsed dc. then rectify that and feed it past the rectifyer on the psu

  9. #19
    Raw Wave Rob Withey's Avatar
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    Quote Originally Posted by DodgeCummins
    Yes, the resistance across the diodes causing the heat transfer, and the voltage drop.
    Diodes are semiconductors, they don't have resistance. Specifically, if the current flow increases, the voltage drop does not increase linearly as with a resistor.


    Rob
    Old Systems retired due to new car
    New system at design/prototype stage on BeagleBoard.

  10. #20
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    Diodes are semiconductors, they don't have resistance.

    Sure they still have internal resistance. Thats one of the reason that limits the amount of power it can handle. A high power semiconductor do have very low internal resistance when they conduct...so it enable them to pass higher currents

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