how ac mains polarity changes

Discussion in 'General Electronics Chat' started by mikemongo101, Feb 22, 2010.

  1. mikemongo101

    Thread Starter New Member

    Aug 19, 2009
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    how does the ac voltage polarity issue forth from the mains terminals specifically, as positive from black to neutral and then negative from neutral to black or what??? i need to know in order to set up my diodes and SCRs with the proper gated polarities. thanks for your considerations in advance.

    mikemongo101
     
  2. Jony130

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    Feb 17, 2009
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  3. KMoffett

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  4. mikemongo101

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    Aug 19, 2009
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    the tutorial only shows that the black and neutral mains only issue negative polarity but receive positive polarity alternations, so why do people portray positive polarity as being issued forth from the mains terminals when this is not the case? I do not under stand this procedure at all!

    mikemongo101
     
  5. KMoffett

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    The polarity at the mains terminals reverse every 0.008333 seconds for 60Hz. Generally they are labled as HOT (black) and NEUTRAL (white). HOT is positive and Neutral is negative for 8.333mSec. Then are reversed, with Hot negative and neutral positive for the next 8.333mS. And so repeat the reversal on every 8.333mS.

    Ken
     
  6. beenthere

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  7. mikemongo101

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    Aug 19, 2009
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    let me redirect the intent of my question, i was speaking of the direction of "electron flow" as utilized by the electronics semiconductor industry with regard to polarity. the assigned polarity that electrical engineers use in drawings and diagrams of basic generators is in the "conventional flow" form which was first used by benjamin franklin and later era engineers. the actual direction of flow was later proven to be the exact opposite and as such was adopted as standard practice by the semiconductor industry. link by kmoffet shows electron flow. only negative to load.
    mikemongo101.
     
  8. KMoffett

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    It makes no difference whether you use conventional current or electron flow, the polarity to the load from the mains terminals 'reverses' every half cycle. Did you distinguish the difference between the "alternator" that generates AC and the "generator" the produces pulsating DC. The term "generator" is a rather generic term and often includes devices the output AC as well as ones that output DC.

    Ken

    Ken
     
  9. beenthere

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    Apr 20, 2004
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    Do you know how to orient your semiconductor devices?

    Are you in need of a polarity detector? -
    That is an issue not particularly related to the regular reversal of polarity on the mains AC supply. We know it will happen 50 or 60 times per second, so we make circuitry that gives the "correct" output that we desire. Knowing the reason for the reversal is immaterial to the circuit design.
     
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