Non Linear Loads

Discussion in 'Homework Help' started by ElecNerd, Jan 30, 2011.

  1. ElecNerd

    Thread Starter New Member

    Jan 2, 2011
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    Hi,

    I am doing an assignment on Harmonics and the textbooks and handouts I am using refer to non linea and linea loads. Please could someone explain what is meant by non-linea loads and an example please?

    Thanks alot
    ElecNerd
     
  2. Papabravo

    Expert

    Feb 24, 2006
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    The basic idea is to ask if the application of a sinusoidal signal at frequency f, produces signals at other frequencies besides f.

    A linear load will NOT produce new frequencies.
    A non-linear load will almost certainly produce new frequencies

    Also:
    non-linear nodes CANNOT be combined using the principle of superposition.

    Q: What is a non-linear load?
    A: A diode.

    You know -- a poem about death.
     
  3. Georacer

    Moderator

    Nov 25, 2009
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    Another typical example is the transistor, with its switching operation.

    ?
     
  4. Papabravo

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    Feb 24, 2006
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  5. Papabravo

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    Feb 24, 2006
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    A doubly balanced diode mixer is another classic example. Two frequencies go in and four frequencies come out. The trigonometric identities to prove it are pretty rough going, but it can be done with high school math.
     
  6. Georacer

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  7. studiot

    AAC Fanatic!

    Nov 9, 2007
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    Muses on Odes

    The original Attic (greek) version was sung.

    The later English version (a la Keats) was not.
     
  8. Georacer

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    Nov 25, 2009
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    "Muses on Odes"
    Are you sure this phrase is correct? A Muse referring to an Ode doesn't make much sense. On the other hand "Ode to the Muse" is more reasonable, and reminds me of something.

    Can you provide a link on some info?
     
  9. studiot

    AAC Fanatic!

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    Again a play on words.

    The classic ( Greek I think ) Muse was a noun - Mythical daughters of Zeus.

    The muse I am referring to stems from classic English referring to semi random thinking about something and is the verb to muse. Modern parlance might say brainstorming.
    The word to amuse is still pretty common, even in these times of cuts.
     
  10. Georacer

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    Ok, I 'll admit that was a good one. I can use English pretty fluently, but the English culture still hides many mysteries from me.

    P.S. The Muses were deities of literature and arts on the ancient Greek mythology. Their descent is diverse and told by many myths, but it is well known that they were invoked by artists to grant them inspiration for their work.
     
  11. steveb

    Senior Member

    Jul 3, 2008
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    The best way to understand this is to define what a linear load is, and then realize that everything else in "nonlinear".

    A linear load obeys the strict form of Ohm's Law which is V=IR, where V is instantaneous voltage, I is instantaneous current and R is a constant independent of everything, at all times.

    There is also a strict mathematical definition of "linear" (which you can Google if interested), but it amounts to the same thing. One confusing thing is that even an offset of the V=IR curve (i.e. V=IR+C, where C is another constant) is "nonlinear". This is confusing because the shape of the curve (voltage as a function of current) is a line. But, this is still NOT a linear load, in the strict sense. Note that this type of nonlinearity looks linear to AC signals, so it does not generate harmonics. When AC signals operate on a part of the load-curve that is not piecewise linear, then harmonics of some type are always generated.
     
    Last edited: Feb 2, 2011
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