What is "power asymmetric"?

vtmaps
vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
in General Solar Power Topics #1
I was looking at the data sheet on Steca Solarix inverters and in the table below (from this document) one of the specifications is "power asymmetric". What does that mean?
Attachment not found.

--vtMaps
4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #2
    Re: What is "power asymmetric"?

    My guess would be, for example, somebody using a 1/2 wave rectifier (battery charging, using a diode to reduce light from a filament bulb, reduce output of a space heater, etc.).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #3
    Re: What is "power asymmetric"?
    BB. wrote: »
    My guess would be, for example, somebody using a 1/2 wave rectifier

    That makes more sense than anything I've been able think of. Do other sine wave inverters have this limitation? --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #4
    Re: What is "power asymmetric"?
    BB. wrote: »
    My guess would be, for example, somebody using a 1/2 wave rectifier (battery charging, using a diode to reduce light from a filament bulb, reduce output of a space heater, etc.).

    -Bill

    Since this inverter offers both 120 and 240 volt outputs, my guess is that 350 is the max power you can draw when only loading one AC phase, while 500 is the output it can deliver to a 240 volt balanced load.

    Not asymmetric waveform but asymmetric (unbalanced) phase loading.
    SMA SB 3000, old BP panels.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #5
    Re: What is "power asymmetric"?

    I don't think any of those inverters are 120/240 VAC split phase...

    As a kid, I had taken an old high intensity lamp and added a diode to make it two level of brightness... Also, ended up cooking the transformer for the lamp (created an average DC current flow?).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #6
    Re: What is "power asymmetric"?
    BB. wrote: »
    I don't think any of those inverters are 120/240 VAC split phase...
    OK, next hypothesis is that asymmetric refers to low power factor? 350 VA at poor power factor, regardless of how much or little the actual watts drawn are? While 500 VA is the output for PF of 1, where VA=Watts?
    Or, it could indeed be a load that only pulls from one polarity of the output, since that would take more peak current during each half cycle to make up the same watt or VA value.

    BB. wrote: »
    As a kid, I had taken an old high intensity lamp and added a diode to make it two level of brightness... Also, ended up cooking the transformer for the lamp (created an average DC current flow?).

    Yes, and a very high one too...
    If you had used a diac, triac or other symmetric breakdown device, which held off on each phase until some voltage threshold you would not have had net DC, nor would you have dissipated much heat in the "dimmer". But the transformer would still have buzzed like crazy. Almost as badly as with a Modified Square Wave inverter powering it. :-)
    -Bill
    SMA SB 3000, old BP panels.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #7
    Re: What is "power asymmetric"?

    Give me a break--An 8 year old with a lamp, a diode, and a soldering iron. :roll:

    VA rating should be Amps RMS--No PF derating needed (for watts). They are very careful about using VA everywhere except where they specify Watts.

    Limiting to 350 VA with Asymmetric current flow(?--Only pulling current on 1/2 of the voltage wave form--i.e., 1/2 wave rectification) would seem that only 1/2 of the FETs would be under load--So that would be a derating to prevent overheating those FETs (i.e., cannot carry full rated VA on only 1/2 the switching transistors).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #8
    Re: What is "power asymmetric"?
    BB. wrote: »
    Only pulling current on 1/2 of the voltage wave form--i.e., 1/2 wave rectification) would seem that only 1/2 of the FETs would be under load--So that would be a derating to prevent overheating those FETs (i.e., cannot carry full rated VA on only 1/2 the switching transistors).

    So then, do many/most inverters (such as my Outback) object to 1/2 wave rectification? --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #9
    Re: What is "power asymmetric"?

    Has anyone contacted Steca Solarix and asked them, or is this more fun? :D
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #10
    Re: What is "power asymmetric"?

    I would assume that any inverter would have problems with 1/2 wave rectification loads... If, as ggunn asks--this is what Steca means.

    I cannot think of any common loads that use 1/2 wave rectification these days (you used to be able to by diodes that would go in a lamp socket under a filament bulb that would allow a lamp to run at "1/2 power"--But I have not seen anything like that for almost 50 years (even then, it was probably just in our junk drawer).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • boB
    boB Solar Expert Posts: 1,032 ✭✭✭✭
    #11
    Re: What is "power asymmetric"?
    BB. wrote: »
    I would assume that any inverter would have problems with 1/2 wave rectification loads... If, as ggunn asks--this is what Steca means.

    I cannot think of any common loads that use 1/2 wave rectification these days (you used to be able to by diodes that would go in a lamp socket under a filament bulb that would allow a lamp to run at "1/2 power"--But I have not seen anything like that for almost 50 years (even then, it was probably just in our junk drawer).

    -Bill

    I believe that a hand held hair dryer uses a diode on the low setting and maybe some other appliances ??

    The typical inverters are designed to be able to run 1/2 wave loads. They have to be able to do that and
    not break at least.

    boB

    PS... Maybe what is meant by power asymetric is any load with power factor less than 1.0 ??
    That would be my guess.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #12
    Re: What is "power asymmetric"?

    I would have thought they were taking Power Factor into the discussion--But given that they define their limits as VA and not Watts--Power Factor does not enter into the discussion as a limiting factor (assuming that they are using RMS volts/Amps / Meter for the V*A rating).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #13
    Re: What is "power asymmetric"?

    So, is someone going to contact the inverter company to settle this bar bet? :D
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #14
    Re: What is "power asymmetric"?

    Nah, we'll settle it in the men's room, more stimulating that way :roll:... yes it is... no it isn't....
     
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #15
    Re: What is "power asymmetric"?
    ggunn wrote: »
    So, is someone going to contact the inverter company to settle this bar bet? :D

    You already answered that question earlier in this thread:
    Has anyone contacted Steca Solarix and asked them, or is this more fun? :D

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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