240w Power Supply at 93.5% efficiency = 256w or 271w at wall?

Discussion in 'General Electronics Chat' started by EdHo, Jun 10, 2016.

  1. EdHo

    Thread Starter New Member

    Jun 10, 2016
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    I have a Meanwell HLG-240H-C2100B power supply (119v, 2.1a, CC, powered by 240v AC)
    powering 3 Bridgelux Vero29 LEDin series. The output from the PS reads 115v, 2.1a = 241.5w.

    Shouldn't the AC Watts "in" measure 258w? (241.5/.935=258)
    I get a reading of 271w in - which suggests an efficiency of 89% not 93.5%.

    Should I be checking the test equipment or is this difference to be expected?
     
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    93.5% is "typical" and based on a specific load.. Did you read the charts in the datasheet?
    Specifically the "Efficiency vs load" chart on page 7

    Not sure what you are using to measure output/input wattage either.. Could be accuracy issues there too,etc...
     
  3. EdHo

    Thread Starter New Member

    Jun 10, 2016
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    If I read it correctly, 100% load is 250w at 93.5% efficiency. Since this load is 241.5w, which is close to full load (96.6%).
    According to the chart, efficiency shouldn't drop below 90% until load is below 35%. As far as "typical", I have checked 6 of these and they yield similar results +-2%.

    I think you confirmed that I need to check the accuracy of the meters.
    Thank you!
     
  4. RichardO

    Well-Known Member

    May 4, 2013
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    Does this mean that you are using two meters -- a volt meter and a current meter?
    If so, you are also measuring the power factor since the voltrage and current are not going to be perfectly in phase. Even a power factor corrected power supply is going to have a less than 100% power factor.
     
  5. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    The tolerance for an efficiency spec rarely is stated, and typically is 5-10%. Also, peak efficiency might be achievable only with a resistive load.

    ak
     
  6. EdHo

    Thread Starter New Member

    Jun 10, 2016
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    A Fluke79 measures the dc output voltage and current. A separate in-line meter measures the AC input voltage and current. (Bayite AC 80-260V 20A).
     
  7. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    The data I found on the Bayite meter didn't say whether it was measuring true RMS or not. However it did say " This module is only suitable for pure AC 50-60HZ the mains." which rather suggests it isn't <surprised>
     
  8. EdHo

    Thread Starter New Member

    Jun 10, 2016
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    Wouldn't LEDs be a resistive load?
     
  9. EdHo

    Thread Starter New Member

    Jun 10, 2016
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    I am not the sharpest tool in the outlet. I "thought" that my municipal power didn't need true rms to be measured correctly...
    Is that not so?
     
  10. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    The voltage should be OK, but the current (input to SMPS) is unlikely to be pure sine.
    [EDIT] What are the voltage and current readings from The Bayite?
     
    Last edited: Jun 10, 2016
  11. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    No. They have a very non-linear voltage-current relationship.
     
  12. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    But they are being fed with a constant current (I think that's what the "CC" in the original post means).
     
  13. EdHo

    Thread Starter New Member

    Jun 10, 2016
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    Bayite numbers for 3 Power Supplies
    247v - 3.39a - 811.9w

    3 Power supplies output
    #1 114v 2.077a = 236.77w
    #2 113.5v 2.097a = 238w
    #3 115v 2.1a = 241.5w
    716.27w total
     
  14. EdHo

    Thread Starter New Member

    Jun 10, 2016
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    Sorry,
    The above should have read:
    Bayite numbers for the AC going into 3 power supplies.
     
  15. EdHo

    Thread Starter New Member

    Jun 10, 2016
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    So do I need a true RMS meter for the AC going into the Constant Current power supply, the DC out, neither or both?
     
  16. crutschow

    Expert

    Mar 14, 2008
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    For the AC power you need a real power meter that compensates for the effect of the power factor, such as a the Kill A Watt meter.
    Measuring the voltage and current separately, even with an RMS volt/amp meter and calculating the VA product, will give you the apparent power, not real power.

    For DC power any DC meter will work since they all measure real (RMS) power.
     
  17. crutschow

    Expert

    Mar 14, 2008
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    The may be non-linear but they are still resistive.
    Being non-linear doesn't make it non-resistive, i.e. the power is still current times voltage drop.
     
    Roderick Young likes this.
  18. EdHo

    Thread Starter New Member

    Jun 10, 2016
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    Thank you.
    Can't find anything like the Kill a Watt for 230v.
     
  19. crutschow

    Expert

    Mar 14, 2008
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    Bummer.
    It's curious that they don't make one since 220V-240V is commonly used in much of the world.
    Perhaps one of these would work.
     
  20. Techno Tronix

    Member

    Jan 10, 2015
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    I agree. Even Kill a Watt meter can really help to cut down on costs and find out what appliances are actually worth keeping plugged in.
     
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