Wiring 130V DC from AC

Discussion in 'The Projects Forum' started by jeff vogt, Mar 13, 2014.

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  1. jeff vogt

    Thread Starter New Member

    Mar 12, 2014
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    Needing some help up here in Alaska to hook up motor to wheat grinder.
    Have a small 130V DC Bodine Gear Drive motor. Model 192. Only pulls .3 Amps, for a wattage of 39.
    Need to put a rectifier, capacitor and in-line fuse in place to convert the AC to operate this DC motor. Have read some posts, but not clear enough for me to understand.
    I know a person can buy an off-the-shelf controller for about $100. But I am hoping I can just add these parts to get it to run (for about $10-$15).
    Problem is I am not sure of the exact parts needed.
    Rectifier I need (a 130V .3A) is not anywhere to be found.
    Bridge rectifier - Our small RS has a bunch of rectifiers/bridge rectifiers, and most appear to be “over-rated” ex: 200V 25A, 200V 50A, 600V 25A. Is it OK to use one of these as it is “over-built”?
    For the capacitor, are their different types? A 10uf be OK?
    For fuses, most at RS seem to be 50 Volts rated…OK to use an in-line fuse with 200V and 1 amp?
    I can build a house, but electronics is greek to me...
    Thx a bunch
     
  2. Papabravo

    Expert

    Feb 24, 2006
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    The only safe way to do it is with a TRANSFORMER, Rectifer, Capacitor...
    I predict imminent thread closure.
     
  3. inwo

    Well-Known Member

    Nov 7, 2013
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    Just use a 25amp rectifier. No capacitor needed.

    1 amp 200v fuse in line side should be fine.
     
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  4. burger2227

    Member

    Feb 3, 2014
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    You could use a bridge rectifier if you know how it hooks up. Bigger voltage and amps the better.

    A 1 amp 150 volt fuse would probably work OK.
     
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  5. wayneh

    Expert

    Sep 9, 2010
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    It is absolutely OK to use an "over-rated" rectifier. Problem: Fully rectified AC is ~170V DC. This might be OK for your motor, or it might not. I'd be a bit nervous. And if you want control you'll need something more anyway.
     
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  6. wayneh

    Expert

    Sep 9, 2010
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    A ghetto solution would be to place a light bulb in series with your motor. On paper a low wattage bulb (12W) would drop the voltage from 170 to 130. You could experiment with bulbs from 7-20W or so, and see what happens at the motor.

    I'd use a capacitor filter as well. I haven't done the math, but I think you'd want at least 1000µF electrolytic in parallel with the rectifier DC poles, with a voltage rating of 200V or more.
     
  7. burger2227

    Member

    Feb 3, 2014
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    RS should have 1N4007 rectifiers good up to 1000 volts. I'd use a fuse and a switch to be safe too!
     
  8. wayneh

    Expert

    Sep 9, 2010
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    I'd use one of the pre-built bridges. Just easier, IMHO.
     
  9. inwo

    Well-Known Member

    Nov 7, 2013
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    No problem with peak voltage, just don't use capacitor.:cool:
     
  10. burger2227

    Member

    Feb 3, 2014
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  11. wayneh

    Expert

    Sep 9, 2010
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    Why not? It'll reduce the ripple.
     
  12. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Full wave rectifier only is fine, this is no different than running a SCR drive, you will only get 90v on 120vac but usually it runs those Bodine motors fine.
    Max.
     
  13. wayneh

    Expert

    Sep 9, 2010
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    You guys are confusing me. (It's not hard to do!) I can accept that you don't need the filter cap, but how do you get 90V DC from rectified 120V AC?
     
  14. burger2227

    Member

    Feb 3, 2014
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    RMS voltage is about 2/3
     
  15. inwo

    Well-Known Member

    Nov 7, 2013
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    Not a resistive load.
    Just as a capacitor input filter increases the voltage above rms. A choke input reduces voltage below rms.

    That's my understanding. I didn't look it up.:p
     
  16. MrChips

    Moderator

    Oct 2, 2009
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    If you were to check out the Terms of Service found at the bottom of the page you will find that there are restrictions on discussion of certain topics. Transformer-less power supplies is one such topic.

    In order to continue with this discussion a AC mains transformer would have to be incorporated into your design.
     
  17. inwo

    Well-Known Member

    Nov 7, 2013
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    I've no dog in this fight.:D

    Technically you may be totally correct.

    In my opinion, a dc motor connected thru rectifier only, with no other components, could easily be thought of the same as any other "how do I connect this motor" question.

    It may be a good place to draw a line in the sand.

    If not, backing up one step, and explaining a proper dc motor connection method, with an isolation transformer, is fine with me.
     
  18. Wendy

    Moderator

    Mar 24, 2008
    20,765
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    Se3ing that this thread is still open I will close it. It is indeed a violation of ToS.
     
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