Testing for sine wave quality

Discussion in 'General Electronics Chat' started by hanajack, Sep 22, 2012.

  1. hanajack

    Thread Starter New Member

    Sep 22, 2012
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    [​IMG] Testing for sine
    I have a military, trailer mounted, 4-cyl. diesel generator made in the mid '50's.
    Use it all the time - I'm off-power. You set the engine speed to the desired cycles and then dial in however many volts you want.

    I would like to know if it puts out true/pure sine but don't know how to determine that. Any advise, tips, information appreciated.
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
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  3. crutschow

    Expert

    Mar 14, 2008
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    Most AC power generators put out a fairly good sine-wave. If you need to measure it then an Oscilloscope is the best way, as suggested by Dd.
     
  4. hanajack

    Thread Starter New Member

    Sep 22, 2012
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    Thanks for that; and the confirmation. I'll check out "Oscilloscopes for dummies".
    Re: "Most AC power generators put out a fairly good sine-wave." Would that apply to one made in the 50's?
     
    Last edited: Sep 23, 2012
  5. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Probably, it's natural for an AC generator to make a sine like waveform as it is a rotating device and sinewaves are a math form that comes from a circle.

    If your AC generator has fixed RPM and you "dial in the voltage" it probably is an AC generator with adustable field. It will probably be sine-like unless overloaded.

    Maybe you should say why you need a good sine shaped AC? There might be specific issues.
     
  6. hanajack

    Thread Starter New Member

    Sep 22, 2012
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    It doesn't have a fixed RPM. The engine speed is adjustable for the purpose of setting the cycles per second on the meter [range 50 to 65]. I rarely have to adjust the engine speed once the cycles are set at 60. [For some reason on the door it says to set it at 61.8 cycles at initial start up - I never do. This is a heavy duty US Army tactical unit I purchased 25+ years ago at a DOD auction].
    With the cycles set, you can dial in whatever voltage you want. I usually dial in 112 to 116 volts due to the length of extensions I'm using. I use to set it at 125 volts thinking of the possible loss of voltage in the lines but destroyed a vacuum motor.
    As to need for true sine, there are no utilities in my area and I use a lot of battery stuff: tools, laptop, cell phone and don't want to damage the batteries - so I never charge them with this generator [go into town for that]. Be nice to charge them when I need to use electric power tools or hair dryer to defrost the gas fridge.
     
  7. crutschow

    Expert

    Mar 14, 2008
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    Generators are normally designed to put out a good sinewave since any harmonics tends to reduce efficiency and increase heating in the generator. If it was designed for the Army, it likely was built very well and I would expect the output to be a good sinewave.

    Generally the only devices that output a sinewave with significant distortion are electronic inverters since it requires a more elaborate and expensive circuit to generate a low distortion sinewave with those devices.
     
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