Increasing AC Current - convert 12dc to ac

Discussion in 'Power Electronics' started by Butch47, Jun 5, 2017.

  1. Butch47

    Thread Starter New Member

    Jun 5, 2017
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    Hey Fellas,
    I need to convert 12dc to ac with as high as possible amps.
    I am currently using a 150W inverter that puts out 240v ac with 10 amps but need more amps.
    Any Ideas???
    Cheers
     
  2. bertus

    Administrator

    Apr 5, 2008
    19,515
    3,975
    Hello,

    Where is the 10 Amps?
    When it is at the input (12 volts side), you are putting in 10 Amps X 12 Volts = 120 Watts.
    Depending on the efficiency of the inverter, you will get likely get about 100 Watts at the output.
    At 240 Volts that will be about 100 Watts / 240 Volts = 0.42 Amps.

    If you want more power, take a larger inverter.

    Bertus
     
  3. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    8,004
    1,355
    What current on the output side do you need?
     
  4. Reloadron

    Distinguished Member

    Jan 15, 2015
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    My guess is you want an inverter and you need to decide what the output waveform can be? You can get a MSW (Modified Sine Wave) or a PWM (Pulse Width Modulation) sine wave or a PSW (Pure Sine Wave)? The latter waveform being expensive. The bottom line is then power. How much power do you need? For example 240 VAC @ 10 Amps for example is 240 * 10 = 2400 Watts. Therefore on the 12 Volt input side this becomes 2400 / 12 = 200 Amps so you will need large cables and a very large battery on the 12 Volt side to get 240 VAC @ 10 Amps on the output side. Those numbers do not even take into consideration the efficiency of the converter / inverter. While 12 Volt input inverters do exist the newer high current models use 24 VDC or higher inputs to reduce the needed current. A 5000 Watt 240 VAC inverter capable of 240 VAC @ 20 Amps would typically be fed using a short as possible length of 4/0 gauge wire (US Standard) and fused at 500 Amps on the input side.

    So what exactly did you want?

    Ron
     
  5. wayneh

    Expert

    Sep 9, 2010
    16,099
    6,210
    Definitely a buy versus make situation. You can't come close to the commercially available units, unless you need something they cannot deliver.
     
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  6. Papabravo

    Expert

    Feb 24, 2006
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    As with an SMPS the power output will always be less than the power input. If this is your first design it will probably be a lot less. I always use 80% efficiency as a starting point. Once you get good at a design you can shoot for 90% or 95%.
     
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  7. EM Fields

    Active Member

    Jun 8, 2016
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    Which inverter are you currently using?
     
  8. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Power out can never be more than power in..
    So please give us specs on your 12VDC power source.. Specifically is maximum wattage..
     
  9. Butch47

    Thread Starter New Member

    Jun 5, 2017
    8
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    Regular auxillery car output, 12vdc 10 amp
     
  10. Butch47

    Thread Starter New Member

    Jun 5, 2017
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    0
  11. Butch47

    Thread Starter New Member

    Jun 5, 2017
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    12VDC 10Amp Input, 240 VAC Output
     
  12. Butch47

    Thread Starter New Member

    Jun 5, 2017
    8
    0
  13. Butch47

    Thread Starter New Member

    Jun 5, 2017
    8
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    Regular auxillery car out put, 12VDC, 10 Amp
     
  14. dendad

    Distinguished Member

    Feb 20, 2016
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    An idea could be to connect the inverter to your car battery directly and not use the cig. lighter socket in the car. This will eliminate some voltage drop in the car wiring harness. I would not run high current through the existing car wires. But remember not to let it flatten your battery.
    But the short answer to getting more power is a bigger inverter.
     
  15. Reloadron

    Distinguished Member

    Jan 15, 2015
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    12 VDC @ 10 Amps = 120 Watts. That 120 Watts at 240 VAC = 240 / 120 = 2 Amps. Actually less because even on a good day your inverter efficiency will be about 80%. So again I ask how much current do you want at 240 VAC? Your original post stated:
    So what you stated makes no sense. An inverter that puts out 240 VAC @ 10 Amps is a 2400 Watt inverter. You stated you wanted more than the 10 Amps you stated you had. A 240 VAC inverter which is a 150 Watt inverter would be 150 / 240 = 0.625 Amp so what is it exactly you want?

    Finally you can't run a 10 Amp auxillary output at a constant 10 Amp current draw unless you have a pocket full of 10 Amp fuses. The maximum you should run is about 7.5 to 8.0 Amps so as not to exceed 80% of the rated maximum. Your auxillary 12 Volt out even at 10 Amps would be 10 * 12 = 120 Watts. That same 120 Watts is as good as it gets so at 240 VAC, as I said you get well below 0.5 Amp.

    The specs on the linked unit are:
    Be sure that your cigarette lighter circuit can supply more than 15 amps.

    Specifications:
    Output Power Continuous: 150W
    Output Power Surge: 450W
    Standby Current: < 300mA
    Input Voltage: 10 - 15VDC
    Output Wave Form: Modified Sine Wave
    Efficiency: > 90%
    Size: 156(L) x 91(W) x 58(H)mm
    Weight: 0.4kg

    So you get 150 Watts @ 240 VAC with a MSW (Modified Sine Wave) which is 150 / 240 = about a half Amp after figuring in 90% efficiency. The Input current will be about 13 Amps. This is why they mentioned a cigarette lighter supplying greater than 15 Amps or at least 15 Amps. You will not get what you originally mentioned as to greater than 10 Amps.

    Ron
     
    Last edited: Jun 5, 2017
  16. EM Fields

    Active Member

    Jun 8, 2016
    583
    154
    OK.
    According to Jaycar, that inverter will supply 150 watts into a load which, with 230 volts RMS across it, will draw I = P / E = 150W / 240V = 0.0625 ampere from the inverter. The inverter is touted to exhibit greater than 90% efficiency, which means that for 150 watts out it'll need about 167 watts in, which is about 14 amperes into the inverter's input with 12VDC across it .

    If you need to be able to supply more current into a higher power load, then probably the easiest way to get there would be to buy a commercially available inverter and use that.
    For example, Jaycar offers this:
    DC AC Inverter.png
    Its spec's also claim >90% efficiency, so 1500 watts out would require 1667 watts in; 12volts X 139 amperes.
     
    Last edited: Jun 5, 2017
  17. Butch47

    Thread Starter New Member

    Jun 5, 2017
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    0
    Is it possible to get a battery with that high a current. And if so, any recommendations as to where i can get one?
     
  18. Rahulk70

    Member

    Dec 16, 2016
    445
    20
    Hi,
    Mate are you seriously considering the 1500W??:eek: You will need one hell of a huge battery/bank of batteries for powering that I guess. But if you are talking about the above 150W inverter it is possible but it depends on the size of your car battery. If your car battery is the normal small one it will pretty much drain the battery real quick than it can be charged and ruin it. Plus the cigarette lighter receptacle (not the ACC one, it handles a lot less) is usually able to handle 10-15Amps max. The lighter pulls around 8.5 to 10Amps, but the lighter functions only for like 15-25 sec so the wiring is able to handle that load and the battery can cope with it. But using an inverter will put continuous load and damage the outlet, wiring and run down your battery unless you have a big bank of truck batteries. Also, vehicle batteries are not meant for heavy continuous deep discharge. Are you planning to use this in an RV?
     
  19. Butch47

    Thread Starter New Member

    Jun 5, 2017
    8
    0
    Nah Mate, just looking for a battery to run it separately, not from a car or RV
     
  20. Rahulk70

    Member

    Dec 16, 2016
    445
    20
    You can get one of those deep cycle solar power batteries. The bigger the better.It will help you run the inverter longer. Look for at least a 12V 20Ah if you plan to run only for brief periods of time. How much current does your load draw at 240VAC?
     
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