DC Power supply rating

Discussion in 'General Electronics Chat' started by superway, May 14, 2015.

  1. superway

    Thread Starter Active Member

    Oct 19, 2009
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    Hello,
    Can I ask you a question about DC power supply?
    I looked many websites, sometimes I see a DC supply 60V/80A the output rating up to 1200W.
    But sometimes I see DC supply 60V/80A and the Output rating more than 3000W.
    What is the difference between of them, even they have the same Voltage and Current?
    Thanks,
    Ken
     
  2. dl324

    Distinguished Member

    Mar 30, 2015
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    There should be no difference, both should have the same power rating. Can you cite some examples?
     
  3. Reloadron

    Active Member

    Jan 15, 2015
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    Watts = Volts * Amps

    A power supply rated to deliver 60V @ 80 Amps is a 4,800 Watt supply. I would have to read the data sheet(s) on any other supplies you are speaking of.

    Ron
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,347
    Hello,

    Do you have links to datasheets of the mentioned power supplies?
    A 1200 Watt power supply will give a max current of 20 Amps at 60 volts and will deliver 15 Volts at 80 Amps.

    Bertus
     
  5. ian field

    Distinguished Member

    Oct 27, 2012
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    Don't forget a small difference between input and output power.

    A switcher should be 80% efficient at the very worst - but I doubt that would account for the difference the TS stated, unless one of them was linear.
     
  6. dl324

    Distinguished Member

    Mar 30, 2015
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    The power rating should be what the output can provide to a load.
     
  7. ian field

    Distinguished Member

    Oct 27, 2012
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    You have to watch out when skimming over adverts - often one or the other power specification is in the small print, or not mentioned at all.
     
  8. Reloadron

    Active Member

    Jan 15, 2015
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    Yes, good point but I haven't a clue where the OP is getting his numbers. :) This is why I always ask for a data sheet, even one written in Chinglish.

    Ron
     
  9. crutschow

    Expert

    Mar 14, 2008
    13,022
    3,236
    It would seem that neither supply can deliver both the maximum current and maximum voltage at the same time.
    Thus the power output (output voltage times the current) can't be more than its power rating.
     
    mcgyvr likes this.
  10. superway

    Thread Starter Active Member

    Oct 19, 2009
    128
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    Thanks for your inputs. Here are the screenshots to show the power ratings, 60V @50A , 1000W. It is not W = VI
    upload_2015-5-14_14-6-21.png

    upload_2015-5-14_14-6-45.png
     
  11. ScottWang

    Moderator

    Aug 23, 2012
    4,855
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    1. Vo=Wmax/Imax=1000W/50A=20V
    It means that when you want to using the Imax 50A then you only can be use with 20V.
    Because the Wmax is limited in 1000W, so you have to using Wmax to divide by Imax 50A.

    2. Vo=Wmax/Imax==1200W/50A= 24V
    It means that when you want to using the Imax 50A then you only can be use with 24V.
    Because the Wmax is limited in 1200W, so you have to using Wmax to divide by Imax 50A.
     
    Reloadron likes this.
  12. superway

    Thread Starter Active Member

    Oct 19, 2009
    128
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    Thanks. How about this model below; it is rated 60A, 85A, 51000W. That is W = 60 x 85 = 5100W. So It is different my previous screenshots ?
    upload_2015-5-14_14-26-48.png
     
  13. ScottWang

    Moderator

    Aug 23, 2012
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    Yes, they are different, so this kind of type will be more expensive.
     
  14. ScottWang

    Moderator

    Aug 23, 2012
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    Some power supplies was designed for the output by wattage, it means that the V/I output will be combined and limited by Watt, maybe this is the one.
     
  15. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,771
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    Yep its UP to 60V and UP to 80A with UP to being important.. You just can't do both at the same time as its limited to how much power it can dissipate
    You can really only do 20A @ 60V..(1200W) or 80A @ 15V (1200W) or any combination that doesn't exceed 1200W
     
  16. crutschow

    Expert

    Mar 14, 2008
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    Yes. Note that you will need a special high current mains outlet to power that supply as it takes up to 24A @ 230Vac at its rated power.
     
  17. ian field

    Distinguished Member

    Oct 27, 2012
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    IIRC: the cooker point is usually rated about 30A or so.
     
  18. ScottWang

    Moderator

    Aug 23, 2012
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    Th posted in #11 were used the max current, the similar when we using the max voltage then the current will be as these:

    1. Io=Wmax/Vmax=1000W/60V=16.67A
    It means that when you want to using the 60 Vmax then you only can be use 16.67A current.
    Because the Wmax is limited in 1000W, so you have to using Wmax to divide by 60 Vmax.

    2. Io=Wmax/Vmax==1200W/60V= 20A
    It means that when you want to using the 60 Vmax then you only can be use 20A current.
    Because the Wmax is limited in 1200W, so you have to using Wmax to divide by 60 Vmax.
     
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