DC load with high amplitude AC component

Discussion in 'Power Electronics' started by powergui, Dec 14, 2017.

  1. powergui

    Thread Starter New Member

    Nov 13, 2017
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    Hi everyone,
    If a DC load with very big AC component (around 1Khz frequency) is supplied by a AC-DC power supply, what would happen? Is there any harm for the power supply?
    I'm having a problem with my AC-DC supplies, when I apply a load with a mean value of 9A (DC), but the AC component has also about 8A peak to peak value with a frequency of 1Khz, my power supplies stop working (something is blown inside) in about 50% of the samples. There is obviously a problem but I wonder is that the high frequency, high amplitude AC component the cause of power supplies' malfunction.
    Thanks in advance.
    Cheers.
     
  2. dendad

    Distinguished Member

    Feb 20, 2016
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    It sounds like you may need a higher current power supply. Also, add low ESR filer caps to the input of the load.
    What is the load anyway?
    More details will help.
     
  3. powergui

    Thread Starter New Member

    Nov 13, 2017
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    Hi dendad,
    Thanks for your answer.
    The load is a radio transceiver, which uses amplitude modulation. The 1kHz frequency of the AC component (unavoidable) is from the audio frequency transmitted by the transceiver.
    Both the amplitude of the AC component and the mean value of the DC component are still well within the current limit of the power supply. I'm just wondering is there any limit of the AC component's amplitude for the load of a typical AC-DC power supply, maybe these supplies are designed to supply constant DC loads with very little AC ripple?
     
  4. dendad

    Distinguished Member

    Feb 20, 2016
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    What is the power supply rated at?
     
  5. powergui

    Thread Starter New Member

    Nov 13, 2017
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    24V, 30A output. The load peak current is still much lower than the rated capacity.
     
  6. dendad

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    Feb 20, 2016
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  7. powergui

    Thread Starter New Member

    Nov 13, 2017
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    I'll try that. But is there any theory related to the amount of AC ripple allowed? Like, is there any way to determine if 8Ap-p is too much for a 30A rated power supply? Or, it can have something to do with the frequency too, as I can imagine, a 10kHz 4Ap-p ripple is even more harmful than a 1kHz 8Ap-p ripple. Obviously these kind of things are not in the power supply's specification sheet.
     
  8. dendad

    Distinguished Member

    Feb 20, 2016
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    I'm sure there are others that can help with the theory calcs. I'd just try a number of low ESR electros that have a fairly high ripple current rating. What in the power supply has burnt? You may have to add RF bypassing to keep that out of the power supply.
    Is the power supply case well grounded?
     
  9. KeepItSimpleStupid

    AAC Fanatic!

    Mar 4, 2014
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  10. powergui

    Thread Starter New Member

    Nov 13, 2017
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    Thanks for all the info, I will try to fix it accordingly.
     
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