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Can AC devices (like heaters etc) work on DC power supply?

  1. May 27, 2013 #1
    Hello,

    Is it possible to run heating and elements and other devices with DC supply?

    I have turned on Nickel-Chromium Heating wires with AC but is it okay to use it with DC supply?

    What's the main practical difference between AC & DC, as long as the voltage and current of supply is similar???

    Many thanks :)
     
  2. jcsd
  3. May 27, 2013 #2

    mfb

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    If you have a simple heating wire, I would not expect issues with DC (as long as the average current is the same). If you have some electronic system, it can require AC.
     
  4. May 27, 2013 #3

    jim hardy

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    Turning it off might get interesting.
    Mechanical switches count on the natural zero crossing of the power line sine wave to help quench the arc.
    DC has no zero crossing so requires a much more robust switch.
    Look at the DC vs AC ratings of a typical switch.

    That'd be the only trouble spot I see for the resistive load you describe.
    Motors driving say a fan or timer are quite another story.


    old jim
     
  5. May 28, 2013 #4
    Thanks :) I see, so even a tungsten bulb will work fine with DC if I have understood correctly.
     
  6. May 28, 2013 #5
    An incandescent light bulb will work just as well on DC if you match its voltage to the RMS rating of the AC supply. For 120 VAC, you'd need 120 VDC etc. They typically last longer on AC, though, since on DC, if I recall correctly, the ionized filament will evaporate from one end and deposit at the other, leaving a thin structure behind to burn through.
     
    Last edited: May 28, 2013
  7. May 28, 2013 #6
    Thanks milesyoung, very interesting indeed... how about heating elements like Silicon Carbide or Nicrome wires, they too last longer on AC?

    I haven't really figured out why is it that the Graphite heating elements are plugged in DC generally speaking...?! Is there any special reason?
     
  8. May 28, 2013 #7
    I doubt it makes any difference in the case of heating elements. Compare the size of a tungsten filament used in an incandescent light bulb to that of the resistive element in a typical household electric heater. The surface temperature of the heating element would probably also be somewhat lower.

    I can't see any reason to prefer DC to AC for powering a graphite heating element. Do you have a reference I could take a look at?
     
  9. May 28, 2013 #8
    I had only read one article sometime back on internet which had a supply of 50V 150Amps DC... but couldn't find anything else...

    There are these AAS (Atomic Absorption Spectroscopy) devices which utilize Graphite Heating tubes, from manufacturers like Buck Scientific... I wonder what the specs of their transformers are... are those DC ?! searched a lot on net but unfortunately not a clue on how many amps/volts either :(
     
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